Dirtbeam: great off-road design, in focus

Also: AAL, add a leaf, extra leaf, helper leaf

An add-a-leaf is an extra steel leaf inserted into an existing leaf spring pack to raise the back of a truck and stiffen it for load, as a cheap alternative to replacing the pack.

Amber light

Also: yellow light, yellow fog lights, amber fog lights, selective yellow, amber lens

Amber light is off-road lighting in the yellow part of the spectrum, and what the manufacturers who sell it claim for it is less glare back from dust and fog, not better penetration through them.

Approach angle

Also: front approach angle

Approach angle is the steepest ramp a vehicle can drive onto without anything at the front touching first, measured between the ground and a line drawn from the front tire's contact patch up to the lowest point ahead of it.

Backscatter

Also: glare back, light blowback, reflection off dust

Backscatter is light from your own lamps hitting airborne dust, fog or snow and bouncing back toward you, and it is why a badly placed light can leave you seeing less than you would with none.

Beam cutoff

Also: horizontal cutoff, cutoff line, sharp cutoff

A beam cutoff is a sharp upper edge to a light's beam, above which it throws almost nothing, and it is the optical feature that makes a wide beam usable when the air is full of dust, fog or snow.

Breakover angle

Also: ramp breakover angle, ramp angle, rampover angle

Breakover angle is the sharpest ridge a vehicle can drive over without grounding out in the middle, measured between the two tire contact patches and the lowest point of the chassis between them.

Candela

Also: cd, candlepower, luminous intensity, peak beam intensity

The candela is the SI base unit of luminous intensity, meaning how much light a source sends in one particular direction, and it is the number that decides how far a light actually reaches.

Center of gravity

Also: centre of gravity, CoG, center of mass, CG height

A vehicle's center of gravity is the single point its whole weight acts through, and how high that point sits above the ground is the largest factor in whether the vehicle leans, tips or rolls.

Color temperature

Also: colour temperature, CCT, correlated color temperature, kelvin, light color

Color temperature is the number in kelvin that says whether a white light looks warm and yellowish or cool and bluish, and it describes appearance only, not how bright a light is or how far it reaches.

Cornering light

Also: cornering lamp, Zone 2 lighting, peripheral lighting

A cornering light is an auxiliary light aimed out to the side rather than straight ahead, so it fills the space either side of the trail that headlights leave dark.

Departure angle

Also: rear departure angle

Departure angle is the steepest slope a vehicle can back down or drive off without dragging its tail, measured between the ground and a line from the rear tire's contact patch to the lowest point behind it.

Ditch lights

Also: auxiliary lights, aux lights, A-pillar lights, pillar lights, cowl lights, hood lights

Ditch lights are auxiliary lights mounted at the hood corners or the base of the A-pillars and aimed outward, so they light the verges, the ditch and the inside of a turn where your headlights do not reach.

Flood beam

Also: wide beam, diffused beam, work light, scene light, flood pattern

A flood beam is a wide off-road light pattern, often forty degrees or more across, that fills the near ground and the sides at the cost of distance, and it belongs low because a wide beam lights a lot of air close to the vehicle.

Four-wheel drive

Also: 4x4, 4WD, four by four, four wheel drive

4x4 means a vehicle with four wheels of which all four can be driven, the first number being the total wheels and the second how many receive engine power.

Ground clearance

Also: running ground clearance, belly clearance, diff clearance

Ground clearance is the distance from the ground to the lowest fixed point under a vehicle, which means it is set by whatever hangs lowest rather than by how tall the tires are or how much lift is fitted.

GVWR

Also: gross vehicle weight rating, gross vehicle weight, weight rating, GVM

GVWR is the maximum loaded weight the manufacturer certifies a vehicle for, printed on a label in the driver's door jamb, and it covers the vehicle, everything bolted to it, everyone in it and everything packed in it.

Hawse fairlead

Also: fairlead, hawse, aluminium fairlead, synthetic line fairlead

A hawse fairlead is a smooth aluminium block that guides a synthetic winch line onto the drum without letting it saw against the bumper, and it exists because synthetic rope does not need the rollers steel cable needs, and is damaged by them.

Hidden winch mount

Also: stealth winch mount, behind the bumper winch mount, concealed winch mount

A hidden winch mount is a bracket that carries a winch behind a vehicle's factory bumper instead of inside an aftermarket one, keeping the standard front end at the cost of approach angle and access.

Independent front suspension

Also: IFS, independent suspension, A-arm front end

Independent front suspension lets each front wheel move up and down on its own, which rides, steers and handles better on the road than a solid axle, at the cost of articulation, clearance under the front differential and some ultimate strength.

Kinetic recovery rope

Also: kinetic rope, snatch strap, snatch rope, recovery rope

A kinetic recovery rope is a nylon rope built to stretch under load, storing energy from a moving vehicle and releasing it to pull a stuck one free, which makes it a different tool from a tow strap and not a substitute for one.

Light bar

Also: LED light bar, off road light bar, bar light

A light bar is a long housing holding a row of LED emitters, sold and mounted as one unit, and its shape is a packaging decision rather than an optical one.

Locking differential

Also: locker, diff lock, differential lock, locking diff

A locking differential forces both wheels on an axle to turn at the same speed, so a wheel with grip keeps getting power even when the wheel on the other side is spinning in the air.

Lumen

Also: lm, luminous flux, raw lumens, effective lumens

A lumen is the SI unit of luminous flux, meaning the total amount of visible light a source puts out in all directions added together, which tells you how much light exists and nothing about where it goes.

Lux

Also: lx, illuminance, one lux distance

A lux is one lumen falling on one square metre, so it measures light arriving on a surface rather than light leaving a source, and it is the unit behind the one lux distance that off-road lamps are advertised by.

Overlanding

Also: overland travel, vehicle-dependent travel, expedition travel, overlanding trip

Overlanding is vehicle-based travel where the journey itself is the point, the vehicle carries what you need to be self-sufficient, and the destination is usually somewhere with no services when you get there.

Payload

Also: payload capacity, carrying capacity, cargo capacity

Payload is what is left of a vehicle's weight rating once the vehicle itself is on the scale, GVWR minus curb weight, and it has to cover the people, the fuel, the gear and every accessory bolted on since it left the factory.

Recovery point

Also: rated recovery point, recovery hook, rated shackle mount

A recovery point is a rated, frame-mounted attachment designed to take the shock load of a vehicle being pulled out, which is a different thing from a tie-down loop, and using the wrong one is the most common way recovery gear hurts somebody.

Rock slider

Also: sliders, rock rails, rocker protection

A rock slider is a frame-mounted bar running along the side of a vehicle that can take the vehicle's full weight on an obstacle, protecting the rocker panel and giving you something to pivot on deliberately.

Skid plate

Also: bash plate, sump guard, underbody armor, skid plates

A skid plate is a panel of steel, aluminium or plastic bolted under a vehicle to protect the engine, transmission, transfer case or fuel tank from rocks, and to let the vehicle slide over an obstacle instead of catching on it.

Snatch block

Also: pulley block, winch pulley, recovery pulley, soft shackle pulley

A snatch block is a pulley you run a winch line through to double the pulling power, halve the speed, or change the direction of a pull, and despite the shared word it has nothing to do with a snatch strap.

Soft shackle

Also: synthetic shackle, rope shackle, Dyneema shackle

A soft shackle is a loop of synthetic rope closed with a knot and an eye that does the job of a steel bow shackle at a fraction of the weight, and with far less to throw if something in the recovery fails.

Spot beam

Also: pencil beam, long range beam, driving beam, spot pattern

A spot beam is a narrow off-road light pattern, typically under about ten degrees wide, that trades width for distance, and it is the only pattern with a good reason to be mounted high.

Traction boards

Also: recovery boards, traction mats, sand ladders, Maxtrax, recovery tracks

Traction boards are stiff ramps with aggressive lugs that you wedge under a spinning tire to give it something to bite on, and they are the fastest self-recovery there is when the problem is grip rather than clearance.

Transfer case

Also: t-case, transfer box, transfer gearbox

A transfer case is the gearbox behind the transmission that sends engine power to the front axle as well as the rear, and usually offers a low range that multiplies torque for slow, difficult ground.

Veiling luminance

Also: disability glare, glare veil, veiling glare, contrast loss

Veiling luminance is the even glow that scattered light lays over everything in your field of view, and it blinds you not by being bright but by shrinking the difference in brightness between an object and its background.

Winch

Also: recovery winch, electric winch, truck winch

A winch is a motor-driven drum that pulls a vehicle out of trouble along a line anchored to something that is not moving, and its rated pull is the figure on the first wrap of line on the drum rather than the fifth.

Plain words for the jargon.