Off-Road Terms Glossary

The distance between the sidewalls at the widest point of an inflated tire not under load.

A semi-floating axle is one that is supported at the inner spline end then is supported by a bearing before the outer end, carrying vehicle weight.

A shim is a thin piece of material used to fill small gaps or spaces between objects. Shims are typically used in order to support, adjust for better fit, or be used as spacers to fill gaps between parts.

The Side Gear is an internally splined gear that receives the axle shaft. The spider pinion gear then drives this gear.

The side portion of a tire between the tread and bead.

The Spanner is also known as a side bearing adjuster. This adjuster is used to move the carrier assembly side-to-side to set back lash.

A normal wrench with one open end and one closed end for fastening bolts or nuts.

Splines are the raised portions that look like teeth. Splines provide a strong and effective way of easily joining two parts together that will need to be removed at a later date. Splines are usually seen as an external (male) and internal (female) receiver variety.

A spool is used to permanently lock axles together. Spools are usually used in competition vehicles that require no differential action between the axles. Spools are not recommended for street use.

The steering knuckle is the main component that allows a solid axle to perform its steering function. The knuckle is usually retained to the housing by the ball joints or king pins.

The Stub Axle is the outer most axle shaft of a multiple shaft assembly.

Standing for short wheel base, usually found in either pickup trucks or SUVs with 3 doors, this refers to shorter wheel base vehicles where the distance between the front and rear wheels are around 90 inches. This often provide more maneuverability off-road, shorter turning circles and better break-over angle, but also are usually less stable on-road and at speed.