track measurement

Track width is measured from the centerline of each wheel. This means that track width of the car can vary with different wheel offsets.

 

Hmmm...interesting...

Like Damon, I'd say the recent technical meaning for "track of a wheeled vehicle" would be "the distance between the tire/wheel centerlines" (or maybe the distance between the centers of the tire-to-ground contact patches), BUT the on-line M-W dictionary has it as most usually to the "outside of the wheels".

george -- Are you really interested in the "track[width] of a suspension" (which I don't think is well-defined) or the "track[width] of a wheeled vehicle"?

 

Finding the wheel/tire center can be difficult, tricky at best. Make it easy by:

If you have wheels on the car without tires mounted, measure the distance from the inside of one wheel lip of one to the outside wheel lip of other.

If wheels have tires mounted but you can measure the width of a wheel at the rim, measure the distance from the inside of one at the rim to inside the other one at the rim and add the wheel width measurement.

Same can be done on tires but can also induce small errors.

 

Track is always defined as wheel centerline, or in reality, the center of the hub between the inner and outer wheel bearings. Generally we want the center of weight focused under the center of the wheel bearings. If the focal point moves off center it puts more leverage on one bearing than the other. Of course we have all seen or used spacers or offset wheels to move that point outward in an attempt to increase track. Many of you who have done this may also have noticed the car no longer steers the same way, because you have moved the point of leverage outward, away from the point originally built into the car. Bump steer will increase as offset moves off center, and at some point become critical.

If you can imagine an invisable line running down from the upper ball joint, through the lower ball joint, and continuing down until it hits the road, imagine where you would want the center foot print of the tire to stand. If you move that footprint inward or outward from the axis of steering, you increase the leverage needed to steer, and in reverse, take more loads from bumps and whatnot. That footprint is called the scrub radius. IIRC, Porsche, in an attempt to gain better handling built into thier cars what they called a zero scrub radius, where they moved the tires footprint directly under the steering axis.

With the front wheels pointed straight, and centered, you can measure the toe-in/out with a trammel guage. If you can get the front of the inner rim to match the distance of the rear of the inner rim you will have 0 toe. If you know what that distance is, add one wheel width and youll have your track. Repeat with the rear axle. I believe the service manual has information on chassis measurments that give precise specs and points of measure.

 

Correct, but if you measure the hub-to-hub distance and then add 2X the wheel offset value that would be equal to the track (as measured to the wheel/tire centers).

 

Oops.. that should've been "then SUBTRACT 2X the wheel offset value that would be equal to the track (as measured to the wheel/tire centers)" to keep the sign convention consistent.