In the process of shopping for wheels, you may encounter questions about your vehicle’s suspension. Whether your vehicle uses stock suspension or a lift kit, it’s important to choose wheels that won’t hit your suspension components or create an unpleasant ride quality. In this guide, we’ll review which wheel specifications are impacted by your vehicle’s suspension and why your suspension plays a key role in determining which wheels will best fit your vehicle.
The interplay between your vehicle’s suspension and wheels is best understood by first defining some key terms.
: If you were to stand at the front of your vehicle and draw an imaginary line between the upper and lower ball joints, that line would be your steering axis. On vehicles equipped with a MacPherson strut system, the strut bearing would serve as the top pivot point instead of the upper ball joint.
This is a vertical line drawn through the center of the tire as viewed from the front of the vehicle.
The distance between the wheel centerline and the steering axis, in relation to the surface of the road, is defined as the scrub radius. If these lines intersect at the surface of the road, zero scrub radius is present. Lines that intersect above the road create a negative scrub radius, and lines that intersect below the road create a positive scrub radius.
The sideways sliding movement of a tire within its scrub radius.
The angle between the vertical axis of your truck and the vertical axis of the wheels attached to your steering linkage (the front wheels in almost every case). Wheels that lean in towards the vehicle at the top have negative camber, while wheels that lean in towards the bottom have positive camber.
Offset is the position of a wheel’s mounting plate relative to the wheel centerline.
The distance from a wheel’s mounting plate to its rear edge is referred to as backspacing.
Suspension and Wheel Choice
A cross section of a MacPherson strut system
A short/long arm suspension with upper control arm visible.
The suspension, wheels, and tires that accompany your vehicle from the factory are designed to work in harmony to create a specific amount of either negative or positive scrub radius (zero scrub is considered undesirable due to poor road feel). A vehicle equipped with factory strut suspension will usually create a negative scrub radius while vehicles equipped with short-long arm (SLA) suspensions usually have a positive scrub radius. In order to maintain factory ride quality, it’s necessary to only use wheels which fall within the backspacing specifications set forth by the vehicle’s manufacturer.