A triangular-shaped suspension component with two pivot points connected to the truck's frame and one point attached to the spindle.


Abbreviation for Antilock Braking System. A computer-controlled braking system that senses impending wheel lockup and pulses the brakes many times a second to prevent it. This results in the most important benefit of ABS: by preventing wheel lockup, it allows the driver to maintain steering control.

Ackerman Angle

(Also known as "toe-out turns".) The turning angle of an inside wheel is different than the turning angle of the outside wheel to account for the fact that the inside wheel travels a shorter path. This difference, which is an engineered value, is called the Ackerman angle. 


Extra spring leaf installed into existing leaf springs and which in most cases lift a vehicle between 1 to 2 inches. Depending on make,  model and the condition of the actual springs. These leaf´s high spring rate will give additional arch to the old or worn springs and increase load capacity.

after-cat system

Exhaust system from the aftermarket that is attached to the outlet side of the last catalytic converter. Basically  it consists of a rear pipe, a resonator, a free-flow muffler and a mid-pipe (X-, H- or Y-pipe). This will provide more power and more sound and a improved gas mileage. A increase in fuel economy is a result of the cat back system due to the fact that the engine has not to work as hard to push exhaust gases through the flowing mufflers. 

air box

Refers to a enclosed chamber that routes fresh air to the carburetor or intake manifold. There are different types of air boxes:  air boxes with integral filter or air boxes with a remote filter on its intake duct.              

air dam

Metal or plastic full-width panel extending down from the front bumper to improve aerodynamics by reducing or modifying airflow. It reduces air resistance and increases the stability of the vehicle by blocking the flow of turbulent air under the chassis.


Describes the reduction of the air pressure in tires. The footprint augments by airing down. This improves traction and off-road capabilities and leads to smooth out the run while driving over rough terrain. Attention! Tire manufactures do not guarantee using their tires with low pressure.

air/fuel mixture

The proportion of air / gasoline in a carbureted gasoline engine. The ideal mixture is basically 14.7:1

Air Locker

A locking differential produced by ARB that engages the side gears using compressed air.

all-season tires

(also known as "4-season tires" or "touring tires") This classification is a compromise between a tyre developed for dry and wet roads (summer) and winter conditions (also for snow covered roads). All-season tires are not able to provide as much grip as a pure winter tyre as required in cold conditions. They are harder compound with softer sidewalls and usually quieter than any type of performance tyre. In addition this all-season tyres have a good ability for water evacuation.

all-wheel drive (AWD)

Drive system which allows all four or more tyres to rotate at a different speed and lacks a multirange transfer case. The wheels are constantly connected to the source of power.


Gauge / display which indicates measurable physical quantities such as velocity (mph), number of revolutions (rpm) or fuel level according to the position of the dial and moveable needle.


To coat a metallic surface (such as aluminum or magnesium) with a protective oxide film through electrolysis (electrical charge). 

antisway bar

Also known as "sway bar", "anti-roll bar", "stabilizer bar". A part of the suspension that minimizes body roll while doing quick cornering or driving over unsteady underground. It provides a prevention of excessive side-to-side body sway.

approach angle

Referring to the maximum approach angle that a vehicle can reach without touching it´s front.


The contact area of the tyre to the road is reduced when water is on the road. In extreme cases, the vehicle hydroplanes (glides) on the water, thus drastically reducing control of the vehicle. Tyres have special tread patterns that ensure optimum drainage of the water away from the tread surface. This effect does, however, reduce proportionally as speed increases. The most effective protection is to adjust driving speeds to the weather conditions.


Refers to the manufacturer of the Air Locker differential and the biggest Australian distributor of all kind of 4x4 accessories.


Refers to the capacity of the suspension to combine compression ("bump") and droop on one axle over unsteady terrain. In the best of cases, the body of the vehicle remains generally level while the axles work at extreme angles when driving on uneven ground.


In general referred to a engine´s breathing system.

asymmetrical tread pattern

An asymmetrical tyre refers to a tyre with a tread pattern that does not form in line symmetry or point symmetry to its central line; it thus has a distinctive inside and outside edge. Asymmetrical tyres may be mounted on either side of the vehicle. Since the tread pattern of many ordinary tyres do not form symmetry in relation to design or pattern noise, the method of mounting tyres is specially prescribed.

axle hop

Refers to the axle housing of the vehicle which is rotating opposite the direction as the tires under acceleration. It snaps back to its original position relatively to the chassis. Sometimes, this motion is repetitive until the driver reduces the degree of acceleration. Also known as "axle wrap".

axle housing

In general the exterior nonrotating casing which is held in place by bearings or bushings and contains the axle assembly on a vehicle (axle shaft, differential, gears that drive the wheels). In addition the axle housing operates as a protective layer for the spinning axle. The whole assembly can crush in case of damage to the axle itself.

axle wrap

Also known as "axle housing" and refers to the rotation of the axle housing. Under extreme acceleration (or deceleration), the rear axle housing of vehicles equipped with leaf-type springs attempts, while applying immoderate throttle, to rotate around the axles as the tires touch the road´s surface. The bending or wrapping of the springs under high-traction conditions is known as "axle wrap". The Springs which are bent into an "S"-Shape have the ability to store spring energy until the tires slip. Occasional risks are breakness of the rear springs, pulling out or breakness of the transmission. This rotation condition affects race vehicles and specially drag racing vehicles.



Indicates the resistance to the free flow of exhaust gases.


Measures the distance (in millimeter) from the mounting plate to the back edge of the wheel and the higher the measure the further into the fender well it will sit. Attention: not to confuse with "wheel offset", which defines the distance (measurement in millimeters) from the backside of the mounting plate to the center line of the wheel.


A acoustic baffle or baffle board inside a muffler to reduce sound (plate, panel). Also known as "silencer" (British English).

balance tube

Also known as "H-Pipe Kit": As a short and laterally sited tube it connects the exhaust pipes on a dual-exhaust system. It balances the pressure and flow between both sides of the exhaust.


At high speeds, tyres generate enormous centrifugal forces. Even tiny irregularities of only a few grams in the tyre are multiplied by many orders of size. Such imbalance stresses tyres and suspension. This weight irregularity can be tested and identified at tyre dealerships and is balanced by adding small counterweights. Every time a tyre is fitted to a wheel, it should be balanced.

ball joint

Refers to a flexible ball joint which consists of a spherical bearing enclosed in a casing connecting the control arms to the steering knuckle. Due to the adaptation of a wide range of angles, it appears mainly in vehicles with front suspension.


Bottom Dead Center. It describes the lowest point at the end of the piston´s down stroke within a cylinder.


The bead of the tyre is that part which sits on the rim. At the center of the bead is the core, which comprises a bundle of steel wires embedded in rubber. This provides a safe and solid seating of the tyre on the rim.

bead lock

A standard bead lock is a two-piece system that clamps the tire bead between the outer and the inner ring. It helps when the tire pressure is insufficient or when airing down for off-roading drives to sustain the bead of the tire.


Refers to a vehicle that is rough or dented on the outside and has seen some stuff. Also known as "hoop die".

bed bar

Indicates a steel bar assembly, usually made form tubular bars. It can be bolted or welded to the vehicle's bed. The bed bars are typically used for style. They do not offer the requested safety of a roll bar in case of flip over while off-roading. Bed bars are useful for the mounting of off-road lights.


A strengthened 4x4 vehicle in comparison with the average ones of the stock.

bell housing

Concerning vehicles with manual transmission, it refers to a bell-shaped enclosure for the clutch and flywheel respective the flex plate and torque converter on an automatic transmission. Replacing the old / corroded bell housing provides the torque converter and flywheel from damage.


Body line that goes along the side of a truck and that separates the lower body from the lower edge of the greenhouse, the roof and the window assembly.

bench race

Discussions about vehicles engine outputs (horsepower) by comparing one engine to another.


A mainly chromed or polished ring that holds the crystal of a chronometer and surrounds headlights or gauges.


Riding either on both right- or both left-side wheels.

bikini top

Used for a soft top variety for the front seats which provides overhead covering and leaves the rear side uncovered. The standard bikini tops are fixed with solid straps to the footman loops at the rear side of the vehicle. Modern types are additionally provided with roof coverage.


1. A part machined from a single piece of metal, not a casting. 2. Aluminum part for the rig.


To remove air in a hydraulic system (hydraulic clutches, brake lines) by pumping out the fluid. This procedure operates by pushing air up as the air soars in a fluid.


1. A quick throttle to rev up the engine briefly.


A fan or compressor that inserts high pressure air into an internal-combustion engine to increase it´s power. Also known as "supercharger" or "booster". 2. Commonly referred to a ventilation system´s engine.

blown engine

Used basically to describe a gravely damaged engine. Also referred to a supercharged engine.

blow the doors off

Means basically to beat a competitor during a speed contest.


Usually referred to a rebuilding of a engine to its own design specs, machining and checking the weight, size, and fit of each component against a manufacture blueprint.


The shortening of a truck, a SUV or Jeep. Usually this adjustment is made for a better departure angle.

body roll

By making a turn the chassis of a truck tends to lean toward the outside as the result of cornering forces. The suspension keeps the wheels in contact with the surface providing grip.


Driving in too high gear for the speed or load when an engine is running below the intended operating range. 2. In relation to mud-bog races it also refers to the mud pit on the race ground.


1. A race vehicle built for mud racing. 2. Refers to the driver of mud-races. 3. Name for off-road-tires used for mud races.


Used for the spinning of tires.


It describes an aftermarket component that can be installed without special modifications or major disassembly, such as fender flares etc.


Refers to wrecking or salvage yard, junkyard.


The procedure of increasing intake pressure above atmospheric pressure (measured in psi = pounds per square inch) provided by a supercharger (booster) or turbocharger. 


1. Machining (drilling, turning, drawing) a cylinder to fit larger pistons. 2. The diameter of a cylinder.


Procedure to increase the size and the power of the engine by combining an enlarged cylinder bore and a lengthened piston stroke. Boring: to bore the cylinders larger for oversized pistons. Stroking: to modify the crankshaft for a longer throw.

bottom end

1. Lower part assembly of the engine that contains the crankshaft, the pistons, connecting rods (which fixes the pistons) and other main engine bearings. 2. Power at low engine speed.


The truck´s suspension reaches the extreme compression limit of its travel by overstressing or overloading it. Further suspension travel is no more available when its bump stops.


By adding a metal plate to an open-channel frame rail or cross member, the frame is strengthened. So a three-sided frame rail can be turned into a four-sided rail.

brake fade

Indicates a loss of braking power because the brakes' friction surface or the brake fluid is becoming overheated.

braking distance

Required distance for braking and to come to the standstill. It depends on the speed, the condition of the road surface and the condition of the tires (especially the tread). It is recommendable to check the tyre tread depth regularly and to provide the vehicle with new ones when worn down to the tread.

break over angle

It refers to the degree of base slope (decline) the defines the largest ramp or hill that a vehicle can travel over without scraping its mid-section between front and rear wheels against the surface. Also known as "ramp break over angle".


Used for a type of winch strap or tow strap that is construed to be attached to two separate points such as the right and left chassis members of a vehicle. At the bridle's center where the straps get together, the bridle serves as a point of attachment for a tow rope, hook etc.


To some extent also referred to a splined cut on a gear or flange. Generally means to pierce or open.

bull bar

To the front structure bolted assembly of a vehicle. It is construed to protect the center and the underside of the front bumper from damage caused by frontal or underside impacts. The bull bars block incoming crash energy from reaching softer front body panels, directing it the  vehicle's structure. They include skid plates on their underside.


Refers to an allegedly indestructible truck couch or part.


1. A level impediment / obstacle. 2. To give a blip to the accelerator ("blipping": just a quick tap to the gas pedal to bring the engine´s rpm up).

bumper bar

Describes a tubular metal strengthening assembly provided with two bars to offer full protection for a front or backside bumper area during minor parking speed impacts. Bumper bars are attached to the steel framework under the vehicle rather than to the bumper itself. It offers a minimal protection during off-roading.

bump steer

A circumstance in which the controlling jerks at an truck couch encounters a knock in the street. Knock steer is frequently created by inappropriate guiding geometry.

bump stick

Mechanical device that controls and limits downward suspension travel. Usually they are installed on both front tires and provides the vehicle with more consistency

bump stop

Elastic or urethane square used to limit the point suspension compression travel.


Intentional spinning or turning of the back tires to heat and clean those tires' tread in preparation of a extreme acceleration from a standing start. Also used to impress onlookers.


Used for a trail impediment that scrapes on a truck's back side end.


cadence braking

Refers to a method of manual braking with the foot brake to simulate the action of ABS brakes. It is effective in slippery condition where brake locking has happened or might happen. The driver applies the footbrake in a series of very quick jabs at the pedal taking the wheels up to the point of brake locking and then let them go before the inevitable fall-off in braking efficiency takes place. Improved braking is provided in any extreme slippery conditions such as ice, snow, wet mud or rain.


An exalted gadget which converts rotating motion into reciprocating movement. Also known as "camshaft".


Refers to the angle of the wheel relative to the vertical (viewed from the front or back side of the vehicle). In case that the wheel leans in towards the vehicle body, the camber angle is negative. If it leans away from the chassis, the camber angle is positive. The angle relative to the drive surface is an essential condition for the cornering force that a tire can develop. So the wheel camber has positive effect on the road holding of the vehicle.

cam duration

Indicates the quantity of time (measured in degrees of crankshaft rotation) that a cam holds open the intake or exhaust valves.

cam lift

Indicates the distance, communicated in thousandths of an inch, toward which a cam opens the valves.


Used for a light brilliance rating. You must consider that not all manufacturers utilize the same technique or method to determine candlepower.


Modern tyres are made of many different materials and components. Looked at schematically, there is the outer cover – the tread and sidewall – and the substructure, the casing. Casing components may include steel and/or textile cord plies, the inner liner (to make tubeless tyres airtight), sidewalls, the apexes, the bead core (keeps the tyre on the rim) and the bead reinforcement.


Refers to the angle to which the steering pivot axis is inclined forward or rearward from vertical (relative to vertical). In case that the pivot axis is inclined backward, the caster is positive. If it´s inclined forward, the caster is positive.

catalytic converter

Describes an emissions-control gadget that routes debilitate gases through a oval-shaped canister filled with palladium and platinum pellets.  It converts the harmful and toxic gases in water vapor, carbon dioxide and less-toxic gasses.


Citizens Band radio. Used for a two-way radio which is regularly utilized for communication between trucks on the trail

center disconnect

Indicates a four-wheel-drive framework that captivates the front axles toward an inboard area rather than the outboard hubs.

center of gravity

Hypothetical middle of mass in a vehicle. It changes due to the passenger load and cargo.


Means clean, done exceptionally or uncommonly in fine shape.


Cubic Feet for every Minute. Used to measure air current through a port, intake manifold, alternately carburetor; an arrangement used to determine carburetor and fuel-injection ability.

chain drive

An arrangement in which a chain and sprockets drive gears instead of the gears being meshed together.


Frightfully terrible vehicle. The opposite meaning is referred as "chick magnet".


It refers to the handles for passengers to grab when the drive gets rough.


Short for microchip: computer's microprocessor (to store computer memory).

chirp the tires

To move rapidly while hard accelerating so that the tires loose currently traction.


Used commonly for the ring-and-pinion gear gathering inside an differential lodging. Also refers when parts are discharged from their functional location.


Indicates the vehicle's whole front sheet metal section, including the fenders, hood and cowl.

coil over

Referring to a suspension that uses shocks for a essential loop encompassing the stun body, regularly utilized with custom-fabricated multilink suspensions because they provide advantages of easy preload and ride-height adjustments, lots of wheel travel and accurate spring dampening / hosing rates. 


Gadget that collects exhaust gases from the debilitate manifold's (or header's) elementary tubes and routes them into a single-exhaust pipe.

combustion chamber

A pit inside the cylinder head(s), exactly over the piston(s), where the combustion takes place.

compression ratio

The total volume of the combustion chamber with the piston completely expanded (max. volume) divided by the total volume with the pistons completely compressed (min. volume). It is a essential peculiarity of an internal-combustion engine. A higher compression ratio usually facilitates a more efficient engine performance. Related issue is the "compression displacement" which defines the alteration of the combustion chamber (in volume expressed in cubic inches or cubic centimeters) while the piston moves from one extreme to the other. It´s related to the horsepower rating of the engine.

contact patch

Part of a tire tread in contact with the road surface.

coordinated tow

During recovering a stuck vehicle, the engine power of both the tug and the stuck vehicle need to be coordinated. This is known as coordinated tow and is usually done by a signal from an external marshaller. To enhance the opportunity of a first-time recovery, the clutches of both vehicles are engaged at the same time.

corn binder

Colloquial (slang) expression for any 4x4 vehicle produced by International Harvester. The company is well known as a manufacturer of farm equipment. Syn.: "Binder"


Referring to a deformation of an unsurfaced track which takes the form of transverse, close-pitch undulations, at right angles to the direction of the track. Also known as "washboard".

crank it

1. Used when the guiding wheel is strongly turned to the left or right. 2. To start the motor.


Refers to the shaft with large, u-molded cranks that are attached to the pistons' connecting rods. It converts the pistons' reciprocal movement into a rotational motion, which forces the drivetrain. Syn.: Crank, wrench.


The least gear proportion in the truck. Found by multiplying the first / initial gear ratio of the low-range rigging proportion of the exchange case by the axle gear ratio ( hub gear proportion).

cross-drilled crank

Indicates crankshafts which are provided with two additional lubrication holes drilled at right angles to each other in the main journal. This procedure provides a high-rpm-bearing lubrication for the main and rod bearings.

Crossover SUV

Crossover Sport Utility Vehicle.

curb weight

Indicates the total weight of the vehicle with full fuel tank, the engine oil at its convenient level, full cooling system (without cargo weight and passengers).

CV joint

Constant velocity joint: two U-joints in a row or a Rzeppa joint which provides a raised angularity of driveline parts. Usually found ahead front drive shafts Furthermore front-drive axles.

cylinder head

Indicates the part on an engine that consists of the valve train and the combustion chambers. The cylinder head covers the tops of the cylinders and pistons.


date of manufacture

A tyre’s date of manufacture is indicated on the tyre sidewall at the end of the DOT serial number (see DOT serial number). Tyre manufacturers have adopted a standard identification system: four numbers that indicate the week and the year of manufacture. For example, the figures 0201 indicate that the tyre was made in the second week of the year 2001.


Refers to a fixed anchor point used during winching like a tree or something else strong enough to remain steady when force is applied against it.  


Used for the surface of the motor block where the head gasket and cylinder sit. 


Commonly used for utilizing a dial pointer and a level wheel to check that a cam's lift and duration is exact. 

departure angle

The greatest point (max. angle) a truck can sink before hitting the back guard or other parts located behind the back tires. 

Detroit Locker

Refers to Locker A, a popular brand of automatic locking differential.


1. Referring to set up a truck's engine, chassis, drivetrain, stereo, or alternately a different framework so that provides most extreme performance. 2. To set up a mechanical part for a operation without inconvenience.


Commonly used for the differential that controls a vehicle's torque and allows it to be diffused at different speeds and is especially important during turns. 

direct ignition system

Ignition system that has no distributor; ignition is sent directly from the multiple modulators (coils to the spark plugs).

direction of rotation

On standard tyres with symmetrical tread patterns, it does not matter which way the tyre is fitted on the rim and in which position it is fitted on the car. However, some tyre manufacturers have started producing tyres with specific directions of rotation in order to improve wet grip and optimize noise generation. The direction of rotation is marked on the side of the tyre with an arrow. This side of the tyre must be on the outside, and the tyre must roll forwards in the direction of the arrow for optimum tyre performance. A number of tyres with asymmetrical tread patterns are also now available which do not have a specific direction of rotation.

directional tire

Tire with a asymmetrical tread that is outlined to provide more traction when rotating in one predominant direction only.

DOT serial number

The DOT symbol certifies the tyre manufacturer’s compliance with the U.S. Department of Transportation tyre safety standards. The DOT serial number is located on the lower sidewall of the tyre, on one side only. Below is a description of the serial number. As of the year 2000, four numbers indicate the date of manufacture – the first two numbers identify the week and the last two numbers identify the year of manufacture. Prior to the year 2000, three numbers indicate the date of manufacture – the first two numbers identify the week and the last number identifies the year of manufacture. To identify tyres manufactured in the 1990s, a decade symbol (a triangle on its side) is located at the end of the DOT serial number. 


A kind of winch fixing that runs the cable to an anchor point and back the vehicle, thereby reduplicating the pulling energy. 


A mechanical device to open both the primary and secondary barrels (a four-barrel Holley carburetor). The mechanical accelerator pumps in both the primary and secondaries.  

drag link

Guiding join that connects the pitman arm to the steering arm. 


Indicates a heavy-duty and D-shaped steel hook used at the end of tow straps, chains or cables that are used to pull or winch a vehicle out of trouble. 

D-Ring attachment

Describes a metal eyehole plate that is bolted or welded in place to serve as an anchor point for heavy-duty metal D-rings or other hooks. These attachments are mounted on some bumpers, grille guards, bull bars and other similar reinforcements. 


Used for any descending suspension travel.

drop the hammer

Commonly used for a quick acceleration from a stop.

dropped pitman arm

An counterbalance arm that lessens the angle between the guiding box and drag connection. 

drum storage capacity

(Also known as "Cable Capacity on the Spool".) The maximum length of cable or wire rope that can be wound around a drum without exceeding the maximum number of layers. It is expressed in feet or meters, and can vary depending on the thickness and diameter of the cable.


"dually": A truck that has dual rear tires on each side.

dual plane

It describes an intake manifold with runners that don't share a normal plenum. Outlined for low- to midrange motor performance. 


Abbreviation for dynamometer, a machine used to measure engine torque either at the flywheel (engine dyno) or rear tires (chassis dyno).



Electronic Control Unit, computer unit for engine management.


Electronic Fuel Injection. A computer-controlled fuel delivery system.


Exhaust Gas Recirculation, an emissions-controlled device that reintroduces burned exhaust gases to an engine's combustion chamber.

electronic ignition

Indicates a ignition system that uses transistorized circuits instead of breaker points.

E.O. Number

Executive Order Number, the number assigned to a part by the California Air Resources Board when it becomes legal to use on emissions-controlled vehicles.


The European Tyre and Rim Technical Organization exists to further align of  national  standards  and  ultimately to  achieve interchangeability of pneumatic tyres, rims and valves in Europe as far as fitting and use are concerned., to  establish common  engineering  dimensions, load / pressure characteristics  and  operational guidelines and to promote the free  exchange  of technical information appertaining to pneumatic tyres, rims and valves. E.T.R.T.O.  Standards are  specifications  of international interest,  including future developments,  approved in accordance with the Organisation's Constitution and Rules of Procedure.

EU tyre label

As of November 2012, a standard label for vehicle tyres became mandatory across Europe. The EU tyre label is based on three criteria and provides information on a tyre’s environmental and safety characteristics with the aim of increasing road safety and reducing fuel consumption.
The tyre label generally applies to tyres for cars, SUVs, vans and trucks. The tyre label only bears limited significance for winter tyres, as winter properties are not shown.

exhaust backpressure

Referring to the resistance to the free flow of exhaust gases through an exhaust system. 

exhaust headers

Performance exhaust manifold built from equal-length steel tubes that is designed to speed the flow of exhaust gases exiting the cylinder head(s).

exhaust manifold

Tubular cast-iron component that routes exhaust gases from the cylinders to the exhaust system.



Commonly used for a steel guide attached onto a winch mount that directs the winch cable. There are two kinds: roller (steel rollers) and Hawse which features a simple bracket with large radiused edges for the cable to rig against. 

fan clutch

A clutch device that is thermostatically controlled and which engages or disengages a mechanical radiator cooling fan according to the motor´s cooling needs.

fitment/mixed fitment

It is recommended that all four tyres be of the same size, construction and speed rating. If tyres of different speed ratings are mounted on a vehicle, the vehicle speed capability will be limited to the lowest speed-rated tyre on the vehicle. It is recommended that the lower speed-rated tyres be placed on the front axle. This should be done to prevent a potential over-steering condition. Vehicle handling may also be affected.

Mixed fitment:
When a vehicle has different tyre dimensions fitted to the front and rear axles, it is said to have mixed tyre fitments. Many powerful vehicle models now come factory equipped with mixed tyre fitments. In addition to the sporty aesthetics this configuration provides, mixing tyre sizes also increases driving safety. While rear-wheel drive benefits from the improved grip of a wide footprint, smaller front tyres help keep the car safely on track (the narrower the tyres, the easier the steering). However, a disadvantage of this configuration is that tyres cannot be rotated axle-wise during seasonal tyre changes (a practice that would be beneficial for even tread wear).


Indicates an early engine that was designed to locate the valves in the block beneath the cylinders rather than the overhead valves as is commonly done. 

flat spot

Describes a momentary decrease in engine power within the power band.


Known as an piston without a dish or a dome. 


It is typical of a vehicle that do not sink on soft going surfaces such as mud or sand due to the large softly inflated tyres.

footprint (tread surface)

The footprint or tread surface is the part of the tyre that comes into direct contact with the road. It is pre-vulcanized and then applied to the carcass of the tyre by means of adhesive rubber. Braking and traction forces are transferred from the vehicle to the road through the footprint.
The tyre tread components (tread blocks, ribs and grooves) are located on the footprint, whereby the tread blocks are designated as the positive portion, and the tread grooves as the negative portion. Footprints differ greatly from each other depending on their intended use (off-road tyres, road tyres, racing slicks). There are also differences between summer and winter tyres. Under German legislation (Road Traffic Regulation or StVO), only tyres with tread on the footprint are permitted on public roads.

forced induction

Referring to "supercharged" or "turbocharged".


Commonly used for a four-cylinder engine. 

four-bolt main

The main bearing caps of a crankshaft that are kept in place by four bolts.


Referring to the drive situation when the front hubs are unlocked and the wheels turn due to the incentive rather than power.


Colloquial (slang) expression that refers to a fuel-injected engine.

fuel injector

An electromechanical gadget that squirts fuel into an motor. 


It describes an axle gathering intended to hold the weight of the vehicle on the axle housing instead on the axle shafts. It contains bearings at both the differential and wheel ends. 


gas shock

A damper shock absorber provided with two separate compartments. One of those contains hydraulic fluid, the other nitrogen gas. In a flexible, moveable separating disc is the gas kept that holds the pressure on the fluid. Thereby, the fluid´s tendency to foam while aggressive driving is reduced.


Physical size (expressed in units of gravity g) which is used to measure the force generated during cornering, acceleration, or deceleration.

glass packs

A tubular kind of muffler: to absorb sound due to the implantation of fiberglass packing. 


Referring to a difficult part of a trail.

granny gear

Indicates an extremely low First gear in a manual transmission: ex. SM465 has a 6.55:1 First gear ratio.


Calamitous failure of a expensive piece. Engines, transmissions and hub assemblies can all grenade.


The upper component of a truck's body. Basically the structure above the beltline, including the roof, windows, and pillars.

grille guard

An assembly that bolts to the front structure of a vehicle designed to protect the center area of the front bumper and grille from damage caused by straight-on frontal impacts. Grille guards serve to block crash energy from reaching softer front body panels, channeling it directly to the vehicle's structure.


Grip refers to how much traction a tyre has on the road. The tyre surface ‘bites’ into the ground surface to ensure driving stability and braking performance. The material properties, tread structure and correct tyre air pressure are the most important factors for achieving the necessary grip. On the one hand, the rubber compound must be soft enough to adapt to the unevenness of the asphalt at a micro level; on the other hand, the structure of the tread blocks (wipers on summer tyres and sipes on winter tyres) must prevent the tyre from sliding in rain or snow. High speeds and wet conditions especially increase the risk of loss of grip. For this reason, the wet grip properties of a tyre is often the deciding factor when it comes to separating bestsellers from substandard products in summer tyre tests.

ground clearance

Indicates the space between the ground and the lowest-lying part of a vehicle's underside. The lowest part (depending on the vehicle) is an axle differential, part of the exhaust system as well as other parts. With the installation of a suspension lift kid the ground clearance can be improved.

ground effect

Used for the reduced airflow under a vehicle due to an air dam and side skirts. Less pressure under the vehicle allows the air passing over its top to push downward which is essential to get an improved grip on the road as well as improved top speed and fuel efficiency. It prevents ground clearance in 4x4's.


Deep, sticky mud.

gun it

To deliberately rev a motor. 


Refers to a triangular metal support that is used to add strength. It is welded in place where two frame rails connect or where two tubes of a roll cage are welded together.


Gross Vehicle Weight Rating. The combined weight and the rated cargo capacity of a vehicle. 


halogen light

Referring to the high-output driving light made of halogen gas inside the bulb. The brilliant effect of the white light is due to the bulb's tungsten filament which can carry a higher current. 


1. Refers to a truck that is completely destroyed. 2. Also known as a truck that has a chopped top or a severely lowered suspension. 


Driver's nickname which is used when communicating on the CB


High-Energy Ignition. A strong and reliable GM distributor assembly with a self-contained coil. 


Indicates a special form of tungsten inert gas welding used commonly on aluminum and stainless steel. 


Describes a stripped thread repair system. It consists of small coil-spring inserts that thread into position on damage female screw threads.


The stuckvehicle is usually caught on its frame on an obstacle and unable to move.


See reverse-rotation.



hole shot

Referring to the beating of a race competitor at the start of a race. Also referred to coming off of a dead stop quicker and coming out of the hole quicker.

hook up

Commonly used for the increase of traction.


Indicates the wheel mounting surface.


Used commonly for a belt driven supercharger.


This expression is used only in past tense. Refers to an engine that has been submerged in water and has sucked water into the cylinders through the intake. Consequently this will no longer rotate because the pistons, which moves up the cylinders, cannot compress the sucked water. 



Independent Front Suspension. It refers to a type of suspension system that allows the two tires on one axle housing to move separately from one another.

intake ports

Describes the passages within a cylinder head that route and direct air and fuel to the intake valves.



Used commonly for an automatic transmission.


kerb weight

The vehicle's weight without load: the empty vehicle + full fuel + 75 kg driver.


Used for a quick downshift on an automatic transmission when is given full throttle.

kicker shocks

Refers to the so called shocks which are installed in a horizontal position between the axle housing and the leaf springs. This kicker shocks are valved with a high rate of compression damping and are intended to reduce axle wrap.


Commonly used for the section of a frame that is curved up to clear an axle housing.


ladder bars

Ladder bars describe longitudinal suspension control arms that link the axle to the frame. It prevents axle wind-up and hop.


Commonly known as the amount of clearance between a valve an a rocker arm or between a rocker arm and a lifter or pushrod.

lateral link

Also known as the tubular suspension rod that positions the axle housing so that a side-to-side movement is reduced while cornering. 


Light-emitting diode. Refers to a small semiconductor that lights up when current is passed through it. Used commonly on some dashboard displays and taillights.


Refers to any 4x4 vehicle that is raised either by a suspension or a body lift. 


 Indicates a spacer that is positioned between the axle assembly and the springs. It´s used to lift a truck inexpensively. Consider the fact that these are only safe on rear-axle assemblies.

light it off

Used commonly for starting an engine.

limited-slip differential

Refers to a final-drive system where the two axle shafts are mechanically attached to a series of churchlike plates to impede wheel spin on slippery road surfaces. It ensures the equal transmission of the engine's power between the two tyres. 


Indicates a path that is selected by the driver and that provides the vehicle with the best route to climb over an obstacle or through a pathway. It is important to choose the right line for a  successful four-wheeling.

load index of tyre

The load Index is a numerical code associated with the maximum load a tyre can carry at the speed indicated by its Speed Symbol under specified service conditions.

load range

See ply rating

locked in

When the manual front hubs are engaged into the lock position.


Referring to a differential lock. A differential lock or locker is a mechanical device in either the front or back differential that sends engine power to both wheels (regardless of traction).

lockers front and rear

Used commonly for the most common truck-owner fibs. 


Used on fasteners to maintain torque.


Refers to an engine assembly consisting of a cylinder block, a crankshaft, a camshaft, bearings, pistons and rings, connecting rods, an oil pump, an oil pan, a timing cover, seals, cylinder heads, and an intake manifold.

loud pedal

Commonly used for the accelerator.

low gears

Refers to the gears that increase the amount of reduction in the transmission, transfer case, or axle. In an axle, they are expressed as the ratio of ring-gear teeth to pinion teeth, so low gears are numerically higher than high gears. (Example: 4.10 gears are lower than 3.55 gears.) Rock crawlers typically have low gears.


Describes when the transfer case is in 4-Lo. Therefore the center differential is locked out (in case the vehicle is so outfitted).


mandrel bend

Indicates a hydraulic or mechanical tube-bending machine that uses dies and mandrels forms to bend tubing in such a way that the walls don't collapse.

manifold cooking

Referring to the use of a hot intake manifold as a heat source for cooking on the trail. 


Mass Airflow Sensor: refers to a device that measures the amount of airflow into the intake manifold. This information, as well as data from other sensors, is sent to the engine's computer, which calibrates the optimum air (fuel and adjusts the EFI system as required.: refers to a device that measures the amount of airflow into the intake manifold. This information, as well as data from other sensors, is sent to the engine's computer, which calibrates the optimum air (fuel and adjusts the EFI system as required.


Commonly used for especially large an aggressively treaded tires.

MIG welding

Metal Inert Gas welding: refers to a wire-feed welding system that uses argon gas as a shielding agent for the weld. Steel, stainless steel, aluminum, and other metals are commonly welded with a MIG welder.


Used commonly for the vehicle's engine. 

modular wheel

Used for a custom or racing wheel with an inner, an outer, and a center section that are bolted or riveted together.


Refers to a type of styling inspired by European performance cars. The bumpers, grille, body trim, and door handles are painted the same color as the body.

mountain motor

A typically bored and stroked big-block engine (to at least 500 cubic inches).

Mouse motor

Refers to a Chevy small-block V-8 engine. It is named Mouse because of its small overall physical size. Some voices indicates that GM executives wanted to scare Chrysler's "elephant" Hemi engine with the new, powerful small-block Chevy.

Multilink Solid-axle

Refers to a suspension design where coil springs are used instead of leaf springs. Furthermore the axle is located by a longitudinal and lateral suspension control arms or links.


nail it

To apply full throttle. 

negative offset

Indicates the mounting surface of the wheel which is outboarded of its centerline while driving. 

normally aspirated

Refers to an engine that relies on vacuum through its intake manifold and cylinders to draw in an air-fuel mixture. Commonly used for an engine without a forced-induction supercharger or turbocharger.


1. Commonly used for: New old stock, which means original equipment, unused parts for vintage trucks, often found in their factory cartons at dealerships. Ant. repro, reproduction. 2. A nitrous oxide injection company. 3. Also referred to: nitrous.



Original Equipment Manufacturer. Refers to the original equipment manufacturer. 


Off-camber describes the situation in which the truck is sideways on an incline, increasing the likelihood of a rollover.

off-road bumper

Replacement bumper (front or rear) that is typically made from heavy gauge steel and that features angled corners and edges that provides extra ground clearance. Where OEM bumpers would normally scrape the ground during steep departure and approach angles off-roading, off-roading bumpers will not.

off-road tyres

Commonly used for off-road tyres for especial use on non-paved roads. The specifics of off-road tyres are a relatively knobbly tread to retain their grip on muddy and sandy underground. SUV's and all-terrain vehicles in general are provided with heavily treaded tyres. 

oil gallery

Refers to the small passages inside the engine block and cylinder heads through where lubricating oil circulates. 


Used for a custom component that is manufactured from plans and which do not have a identical copy. 2. Refers also to wide-productions modifications to actual existing vehicle such as a "Saleen Explorer". 

out to lunch

Used commonly for a vehicle that do not run well or do not look right.


This term describes a rugged, outdoor adventure, usually to a remote area. It is commonly associated with heavy-duty 4x4 vehicles.


When the rear tires slide toward the outside of the turn while cornering. 


P-metric tyre

Refers to P225/60R18 99H. The "P" on the tyre size designation defines a "P-metric" size that was construed to be fitted on vehicles that are generally used as passenger vehicles (cars, minivans, SUV's) and light duty pickup trucks with typically 1/4- and 1/2-ton load capacity. "P-metric"-sizes are common since the late 1970's and represent the most used type of tire size in these days.

Panhard rod

Describes a transverse link or rod that is attached to the vehicle's frame at one end and to the axle housing at the opposite end. Panhard rods provide lateral positioning of the axle housing relative to the chassis.


A component that is broken and can not be repaired anymore. It can be simply used as a paperweight.


Used for the maximum weight a vehicle can carry. It is calculated by subtracting the curb weight of the vehicle and a 150-pound allowance for each passenger from the gross vehicle weight rating. 


Refers to an open differential. "One-legger" is an other expression for a open differential. 

pickle fork

A tool in form of a fork used to separate suspension parts for repair (ball joints, tie-rod ends etc. ). 

pinion angle

Indicates the angle of the pinion yoke on an axle housing in relation to its driveshaft. 

pitman arm

Steering lever that converts the rotary motion of the steering box to the linear motion of the steering system's center link.


Referring to a box or cavity at the entrance of the intake manifold that stores the air and fuel mix for distribution to the intake runners. 


Also known as "understeering".

ply rating

Referring to load range that is branded on a tire's sidewall. A load range / ply rating identifies the amount of load the tire is capable to carry at its industry specified pressure. The passenger tires feature named load ranges. The light truck tires use load ranges that ascend in alphabetical order. The further the letter goes along the alphabet the stronger the tires are that can withstand higher inflation pressure and so carry heavier loads. Before load ranges were adopted, ply ratings and/or the actual number of casing plies were used to identify the relative strength with higher numeric ratings or plies identifying tires featuring stronger, heavier duty constructions. Today's load range (or ply ratings) do not count the actual number of body ply layers that are used to make up the tire's internal structure. But it indicates an equivalent strength compared to early bias ply tires. 

POR tyre

"Professional Off-road" tyre is subgroup of special use tyre primarily used for servicing in severe off-road conditions. POR tyres are excluded from labelling, since they are specially designed to reach exceptional adherence performances in poor conditions and in all

port injection

Related to a electronic fuel-injection system that introduces fuel directly into the cylinder-head ports. 


"Posi-traction". It is a limited-slip differential used by General Motors. Commonly used for any limited-slip device.

positive offset

Refers to the mounting surface of the wheel which is inboard of its centreline.


Used for an off-road truck that is built to prerun a desert race course and provide the possibility to study and to practice the course before the race.

progressive-rate springs

Used commonly for the suspension springs that are getting progressively stiffer as they are compressed.

proportioning valve

Refers to the hydraulic braking valve that varies the braking force at the front or back wheels, depending on pedal pressure, load and weight transfer, to minimizes or eliminate wheel lockup. 


Power Take-Off. Refers to an accessory powered by engine output such a winch. 


Commonly used for the cent resection of an axle housing where the differential carrier and gear set are placed. This is also known as "coconut", "third member".

push bar

Refers to metal bar(s). An extension to a grille guard or add-on to an off-road bomber designed to align with the bumper of another vehicle. This allows you to use your vehicle to push another without damage since pressure is hardly applied. "Pre-runner" are referred to horizontal push bars.


Indicates thin metal rods that transmit the move from the camshaft and lifters to the rocker arms. Thus operate the valves on an overhead-valve (OHV) engine. 



Refers to a four-barrel carburetor as well as to a four-wheeled all-terrain vehicle. 


Side panel used as a body shop term for the front or back corner sheet metal assembly. 


radial tyre

Referring to radial tyres that are provided with body cords that run across the tyre, nearly perpendicular to the beads. They have belt plies which are laid diagonally under the thread and provides stability and strengthen the tread area and add flexibility to the sidewall. During contact with the surface, the belt plies increase tread life by restricting tread movement. It also improves handling.

radius arms

Refers to brackets or clips used by Ford that locate the front axle housing on coil-spring suspensions. Dodge and Jeep use similar brackets. Also known as "trailing arms" or "control arms". 


Used for a steering system. It uses a pinion gear at the end of the steering shaft to engage a horizontal toothed bar, the rack, which is connected to the tie rods and the steering knuckles. 


Used commonly in case the frontend of a vehicle is lower positioned than the rear. 

ramp break over angle

Refers to the angle formed by lines drawn from the front and rear tires' contact patches and the midpoint of the wheelbase on the chassis. The greater the angle, the less likelihood of high-centering. 


Used commonly to chevy big-block V-8 engines which are normally offered in 396ci, 402ci, 427ci, and 454ci sizes. It was named because it was a large companion to Chevrolet's small-block Mouse V-8.


Used when after a suspension spring is compressed by a bump, the spring naturally tries to return to its previous length, extending the suspension upward toward its original ride height.

recirculating ball steering

Recirculating ball steering describes a steering assembly that uses a worm gear on the end of the steering shaft to turn a sector gear that is within the steering box and linked to the pitman arm. For smooth operation ball bearings are used between the worm and sector gears.


Indicates the absolute maximum engine speed (expressed in rpm), at which an engine should be operated (red line on the tachometer). Also known as " rev limit".

Reinforced or XL (extra load) tyres

Reinforced or XL (extra load) tyres are specially reinforced tyres. They can carry higher loads than a tyre of the same size. Reinforced tyres are designated on the sidewall by the letters “RF” and extra load tyres with the letters “XL”. Reinforced and XL tyres require higher inflation pressures compared to standard tyres.


Aftermarket reproduction parts, manufactured to appear, fit, and function as originals. Not the same as OE or N.O.S., which are both factory-issued parts.


To build a truck that is basically restored but has been updated with modern convenience and performance enhancements.


When installing new parts or systems on an older truck for the purpose of upgrading, such as retrofitting a modern fuel-injection system in place of the original carburetor.

rev limiter

Electronic device that is adjustable and restricts engine rpm to a predetermined limit so engine damage does not happen.


An axle design where the pinion is positioned above the axle centerline.


Related to lifestyle (used for a custom fab off-road vehicle).


Refers to the gear set that drives the wheels. The pinion is a gear linked to the rear of the driveshaft. The ring gear is part of the differential that turns the axles.

rock magnet

Used for a low-hanging component of a 4x4, such as a ladder bar. It seems to catch on every obstacle.

rock massaging

Body damage caused by rocks and other obstacles on the trail.

rocker arm

Used for pivoting valve train levers. One end of an engine's rocker arms are moved by the pushrods or lifters and the opposite end's open intake or exhaust valves.

rocker bar

Rocker bars are bolt to the frame along the sides of the vehicle. It protects vulnerable rocker panel body pieces that can get damaged during off-roading. Also known as "rocker guards". 

rocker panel

Indicates the sheet metal section of a truck's body located below the doors and between the front and rear wheel openings.


Used for axles that are easily identifiable due to their square axle tubes and pinion that sits on the top of the axle. They were originally used in military 6x6 2.5 ton trucks. 

rolling circumference (tyre)

The distance covered by a point on the circumference of the tyre when the tyre revolves once at 60 km/h (37 mph).

rolling resistance

Rolling resistance refers to the drag force required to put a free rolling tyre into motion. Tyres are not rigid, but flexible. During driving, the tyres compress and flex – and this flexing absorbs energy, converting it into heat. In order to reduce rolling resistance, manufacturers use special rubber compounds. Any reduction in the rolling resistance of the tyre helps reduce fuel consumption. Since rolling resistance also increases with low inflation pressure, it is beneficial to check tyre pressure regularly.

Roots supercharger

Commonly used for positive-displacement, belt driven supercharger. Roots supercharger were originally designed in 1859 by Francis Roots for use as a water pump.


Ramp Travel Index. A measurement of suspension flexibility and articulation. It is calculated by dividing the distance the hub's centerline travels up a (usually 20-degree) ramp by the vehicle's wheelbase in inches, multiplied by 1,000.


sand ladders

Designed to increase tire grip, sand ladders are a form of traction aid consisting of a pair of ramps with perforations and which are placed beneath the wheels of a vehicle that has become stuck in muck or snow. It provides a solid traction surface that would not otherwise exist.


Used for well designed, engineered and constructed components of a vehicle (when cleanly built, superior mechanical workmanship). Syn. sano.


A part of the axle assembly that carries the weight of the vehicle on the axle shafts. These are typically weaker in comparison to full-floaters.

serpentine belt

Refers to an engine accessory which is drive belt and long. It follows a snaking path while driving the alternator, water pump, A/C unit, and power-steering pulleys.


The shackle is the connector between the rear of a leaf-spring pack and the frame. It allows the spring to lengthen while the suspension is compressed.

shift kit

Indicates a package of high-performance components for an automatic transmission that firms the shifts, alters the shift points. It improves overall performance of the vehicle. 

shiny-side down

Used hen a truck rolls over. Also known as "rubber-side up".


Used for an engine block that has a complete bottom end (including the crankshaft, rods, pistons, and camshaft). But without the cylinder heads, intake and exhaust manifolds, water pump, and other accessories.

side hill

When a portion of the trail leads across a steep hill instead of up or down. See "off-camber"

single-plane manifold

Refers to an intake manifold with a single plenum feeding all of the engine's intake runners.


The tread blocks of a tyre have tiny slits called sipes. Sipes are able to open and close, optimizing the traction and braking forces applied on the road (grip edge effect). Sipes are mainly important for winter tyres, guaranteeing better grip on snow slush, ice and wet road surfaces.

skid plate

Refers to a flat metal plate that bolts onto the frame, the grille guard, the bull bar or bumper of the vehicle. It provides protection for mechanicals behind it such as oil pans, differential, steering linkages, etc. These items are especially vulnerable when off-roading over unsteady underground.


Used for body sheet metal.


Commonly used for tires.

slick rock

Refers to a type of sandstone dominant in Moab, Utah. Basically Slick rock is not slick and provides excellent traction.

slush box

Related to an automatic transmission. Also known as "juicebox".


Used for a V-8 engine which has typically 400 or less cubic inches of displacement.


It is a guide roller or guide pulley often used in combination with a winch to get vehicles unstuck.

snatch strap

A thick nylon strap used to pull out stuck vehicles. Syn. tow strap, yank strap.

snowflake-on-mountain symbol (Alpine symbol)

The Alpine symbol identifies winter tyres according to UNECE regulations (valid in the EU and various other countries) and the tyre regulations of the USA and Canada. The snow performance of these winter tyres has to be proven by objective tests and meet or exceed defined limits. These tyres provide high performance with regards to safety and control on snow, on icy roads and in general at low temperatures.

spare tyre

The spare tyre may only be used in an emergency for temporary, limited use on one wheel of the vehicle with the agreement of the vehicle manufacturer.

speed symbol (SSY) of tyre

The Speed Symbol indicates the maximum speed at which the tyre can carry a load corresponding to its Load Index.

spool out

Used when the winch cable is pull off the drum after releasing the brake.


A spotter is a co-driver who helps guide the driver over obstacles by using hand signals.

spring rate

Requested force to deflect a spring 1 inch (expressed in pounds per inch of spring compression or deflection). The higher the per-inch spring rate, the stiffer the spring.

spun bearing

Used commonly for a bearing that is either worn or frozen and has rotated in its retainer. In general, the bearing to block off its oil passage in an engine produces greater damage.


Means an obstacle that contains one or more ledges that must be climbed in succession. They are common on trails that follow washes or creek beds.

stand on it

Used commonly for a full-throttle acceleration.

static radius (tyre)

The distance between the wheel center and the ground contact patch under maximum load at the recommended tyre pressure.

stinger bar

Stinger bars defines a front-mounted assembly which is an extension to a grille guard or an add-on to an off-road bumper. Stinger bars are angled upward at a steep rake to impede the vehicle's tumbling off its wheels onto the front end. They are especially useful when the driver tries to slide out of a hole without burying the vehicle's front end.

summer tyres

Summer tyres are specially designed for use in high temperatures. Their material composition achieves significantly better performance in terms of fuel consumption, wear and driving performance in warm temperatures than with winter tyres. Their tread is also optimized for driving in both dry and wet conditions. The ‘wiper effect’ they provide ensures short braking distances and high driving stability even on wet roads.


When the engine or the entire truck is drowned. 

synthetic oil

In comparison to the standard mineral oil, synthetic oil is in general provided with a bigger capacity to lubricate and resist. Also called "manmade lubricants".



Gadget used to measure and display engine speed (expressed in revolutions per minute). The short form "tach" is also used.

tack welds

Refers to series of small welds which are spaced approximately 1 inch apart and used to hold together two pieces of metal until the final welding can be performed.


Used commonly for axle housings, frames, or other components that have been severely bent. Usually from jumping the truck.

tail gunner

The last vehicle/driver on a trail ride. The tail gunner is responsible for making sure everyone completes the trail.

tall gears

Tall gears are the opposite of low gears. They are represented in ratios that are numerically lower than "low" gears; e.g., 3.08s are taller than 4.10s.


Throttle-body fuel injection.

threshold braking

When the brake pedal is applied as much pressure as possible without going to wheel lockup.

throwout bearing

On a clutch assembly, a shaft-mounted bearing that is moved from pressure on the clutch pedal and disengages the clutch disc from the engine.


Transfer case.

tie rod

Steering linkage between the pitman or idler arm and a steering arm that moves the steering knuckles.

TIG welding

Tungsten Inert Gas welding, also referred to as heliarc welding, usually used for joining aluminum and stainless steel.

timing chain/gears

Chain or gears that transmit rotation from the crankshaft to the camshaft.


The toe describes the distance between the centrelines of the tyres on an axle. The toe setting can be adjusted on all cars. Since most wheels tend to run towards the outside because of the camber, most cars are set with a slightly positive toe-in. This means that the wheels are slightly closer together at the front than at the back. Incorrect settings for your vehicle result in uneven tyre wear. If you notice uneven tyre wear, then have your vehicle alignment settings checked.

toe-in, toe-out

Inclination of a pair of front wheels slightly inward or outward as viewed from the truck's front.


Torque is the force created during rotation. This is an important consideration during off-road fabrication.

torque converter

It describes fluid coupling between the engine and the automatic transmission. The engine powers a fan-shaped impeller inside the torque converter, which splashes oil onto a turbine which is another fan-shaped device. The turbine transmits its power to the transmission's gearbox.

torsion bar

Refers to a suspension spring similar a long metal rod which one end is connected to the truck's frame and the other end is linked to the suspension's A-arm. The torsion bar is twisted when the A-arm moves, and then springs back to its original shape, thus its springing action.

tow bar

They allow one vehicle to pull another one behind it with 4 wheels rolling on the ground. It is for those who do not have a trailer. A single bar on one end is linked to the tow hitch of the one vehicle, then splits into two bars that is attached to the frame (or D-ring hooks) of the vehicle being pulled.

tow hooks

Heavy-duty forged steel hooks bolted or welded to the front or rear of a vehicle frame that serve as attachment and pulling points for snatch-em straps and winch cables.


Tuned-port fuel injection.


The Tire and Rim Association, Inc. (TRA) is the standardizing body for the tire, rim, valve and allied parts industry for the United States. TRA was founded in 1903 and its primary purpose is to establish and promulgate interchangeability standards for tires, rims, valves and allied parts. TRA standards are published in the Tire and Rim Year Book, Aircraft Year Book and supplemental publications. TRA membership is limited to manufacturers of tires, rims and wheels and allied parts. TRA has available rim inspection material (tapes and gauges) to check rim contours to TRA standards.

trail boss

So called leader of a trail ride.

trailer queen

Primarily built for shows and is just trailered to events.


The tread is that part of the tyre with the groove pattern that is in contact with the road. The tread is specifically designed to provide traction for stopping, starting, cornering and providing long-lasting wear.

tread depth

The measured distance from the tread surface to the bottom of the main grooves away from the tread wear indicators. It is usually specified in millimeters.

Tread Wear Indicator (TWI)

Tread Wear Indicators are raised bars placed in the longitudinal grooves evenly around the tyre. If the tread pattern is worn out up to 3 mm for summer tyres and 4 mm for winter tyres, the Tread Wear Indicators become level with the tread pattern. Tread wear indicators are also placed at 1.6 mm, the legal minimum tread depth for both summer and winter tyres. We recommend changing to new tyres when your winter tyres reach a tread depth of 4 mm and your summer tyres a tread depth of 3 mm.


Twin-Traction Beam. A type of Ford front suspension that utilizes an axle assembly with pivot points. This allows the tires to move independently.

tunnel ram

Refers to an intake manifold with a large plenum and long, straight runner. It is used for high-rpm engines.

turned turtle

When the vehicle is rolled upside down.

two-bolt main

Refers to an engine block which its main crankshaft caps are kept in place by two bolts.


While doing a tricky maneuver and the tires lift off the ground. Also known as "bicycling".

tyre size designation

In the case of a 185/65R14 tyre, the figures mean the following: 185 = width of tyre in millimeters; 65 = the ratio of the height to the width as a percentage; R = radial construction; 14 = diameter of the rim in inches.



Bolts which are u-shaped and commonly used to attach an axle housing to a leaf-spring pack.


This mechanical joint can transmit rotary motion while the vehicle is swiveling. U-joints are used at both ends of a driveshaft to transmit power from the transfer case to the differential.


Commonly used for the cornering condition where the front tires lose grip before the rear tires, causing the front end to slide or push toward the outside of the corner.


When the vehicle is damaged or destroyed. For example: a blown-up engine has become unglued. 


vacuum advance

Refers to a device that advances or retards the ignition timing according to the degree of engine vacuum. The ignition is advanced when there is plenty of engine vacuum at low engine speed. Otherwise, at wide-open throttle, there is little vacuum, so the ignition remains at its original timing advance. 

vacuum secondaries

Secondary carburetor barrels that are pulled open by engine vacuum.

valve lift

A circular device used to control the airflow in and out of an engine. It is operated by the camshaft or pushrods or rocker arms.

valve train

Includes components such as the valve lifters, pushrods, rocker arms as well as the valve springs.

vapor lock

Used commonly for the condition where fuel boils within the fuel line or carburetor.

variable-ratio steering

Refers to the power-steering box that varies the steering ratio. The steering response is quicker for maneuverability at low speeds, at high speeds, the steering ratio is reduced for stability.

ventilate the block

Means to throw a connecting rod through the side of an engine block due to either a component failure or excessive revs.


Used for the carburetor barrel or throat with a slightly narrowed or hourglass shape to its interior and which the small, narrowed area speeds up airflow and helps pull the fuel past the carburetor jets and into the air stream.


Vehicle identification number, a serial number that identifies a vehicle.



A performance at peak power or efficiency.

wheel adapter

Refers to a metal plate provided with wheel studs that allows a wheel with one bolt pattern to be used on a vehicle with a dissimilar bolt pattern.

wheel alignment

A wheel alignment adjustment may be necessary if the vehicle pulls to the right or the left when the steering wheel is in the straight-ahead position. Uneven tyre wear is another indicator of the need for an alignment check.


Refers to the distance from the center of a vehicle's front wheel to the center of the rear wheel on the same side.

wheel hop

When an axle of a 4x4 vehicle quickly hops up and down. Not to confound with "axle wrap". This is a involuntary suspension motion that allows the pinion angle to change. In case of drivetrain breakage the reason is not the hopping but the axle wrap that is a consequence of the hop which is the cause of drivelines that breaks yokes, drive shafts and occasionally pinions.

wheel travel

Refers to the total distance a wheel can move up and down. It is affected by suspension travel and wheelwell 


Related to an obstacle that is difficult and scary enough to make the driver grip the steering wheel extremely tight.

windage tray

Windage tray indicates an internal engine shield which is mounted close to the crankshaft and is designed to deflect oil away from the crank as it rotates.

winter tyres

Winter tyres are specially developed for use in low temperatures and for driving in wintry conditions. Their tread blocks have a large number of sipes that ensure sufficient grip even on slick roads. The material compound is also carefully selected to keep the tyres elastic even in the cold. At high temperatures, however, winter tyres become too soft, which is why they should not be used during the summer.

wiring harness

Major part of a truck's electrical wiring system; a group of wires bundled together.


Wide Open Throttle.

wrist pin

Describes a hollow metal tubular pin that links the piston to the connecting rod.


zerk fitting

Indicates the nipple like fitting on suspension and chassis parts as well as on U-joints. Lubricant is pumped under pressure so to lubricate the components' internals.

Since 1915.
General Tire. A brand of Continental.