track

Track is the lateral distance between the centerlines of two wheels mounted on the same axle, measured perpendicular to the vehicle's direction of travel. On a car or truck, front track and rear track are measured independently; they are often different from each other. This dimension is fundamental to suspension design, steering geometry, and overall vehicle stability.

Track width directly affects a vehicle's resistance to rolling during cornering. A wider track lowers the center of gravity relative to the pivot point of the vehicle's body during a turn, which reduces the likelihood of tipping. Wider track also improves the mechanical advantage of the suspension components and distributes lateral forces more evenly across the tires. Conversely, a narrower track reduces unsprung mass and can improve ride comfort on rough surfaces, but at the cost of reduced cornering stability.

The relationship between front and rear track influences handling balance. When the rear track is narrower than the front, the vehicle tends toward understeer; the rear swings out less readily during a turn. When the rear track is wider than the front, oversteer tendency increases. Manufacturers adjust this difference by a few inches to tune the handling characteristics of each model. Heavy trucks often have dual rear wheels, which increases rear track significantly and improves load stability.

Practical constraints and measurement

Track width must clear the vehicle's body and fenders, particularly at the wheel's outermost points during suspension droop and compression. It is also constrained by the width of available axles and the diameter of brake drums or rotors, which sit inboard of the wheel. Track is typically specified to the nearest quarter inch in automotive engineering. Measuring track accurately requires measuring from wheel centerline to wheel centerline while the vehicle is at rest on a level surface with correct tire pressure and no load.

The term track derives from the physical path or "track" that repeated wheel passes wear into the ground, implying the spacing between those parallel marks. Do not confuse track with wheelbase, which is the distance between front and rear axles, or with gauge, an older synonym that persists primarily in railway contexts where it denotes the spacing between rails.