You didn’t sleep through highschool geometry class, now did ya? You’re gonna need some of those math skills now if you really want to understand your race car’s steering and suspension. To understand the real nitty-gritty details of how they work, you better go back and get your Engineering degree. But with a little patience, some homework, the right tools, and a lot of practice, you can save ALOT of money in the long run adjusting your steering and suspension yourself, instead of paying someone else to do it for you.
Cars from the factory are not very adjustable, the engineers decided for you what you get, and that’s it. But with a race car, you can adjust for the demands of each and every racetrack. Adjusting the steering geometry of your race car will change three important characteristics; how quickly it reacts to steering inputs, how much tire patch remains on the track while cornering, and how straight and stable it tracks down the straightaways. The three adjustments that change these characteristics are toe, camber, and caster. The problem is adjusting one will affect the others, so only make one adjustment at a time, and then do your testing. Factory cars only have adjustable toe; the difference in distances when measuring between the leading edge of the front (or rear) tires and the trailing edge of the tire. Increments are commonly measured in 1/16ths of an inch, and yes, measurements that small make a difference. A little bit of toe-out (the distance between the leading edges of the tires is greater than the distance between the trailing edges) on the front tires creates a car that reacts quickly to steering input. About 1/4″ of toe-out is a starting point for many race cars. A little bit of toe-in on the rear (1/8″) will stabilize this increase in steering reaction, a little bit of toe-out will destabilize it. Zero degrees of rear toe is a common starting point. Camber (specifically, negative camber) is the angle of lean the top of the tire has towards the centerline of the car. A straight up and down wheel has 0 degrees of camber, and it causes the tire to “roll-over” onto the outer sidewall during heavy cornering loads. Increasing negative camber allows the tire to remain on it’s contact patch while the car is leaning over, increasing traction and diminshing tire wear. Add too much however, and you start to wear out the inner part of the tire. Negative 2-3 degrees camber is a starting point for most race cars with adjustable camber. Caster is the angle of the steering pivot axis. This is only adjustable on a custom race suspension. Think of a shopping cart wheel, the axis of steering is ahead of the wheel when you push the cart forward (positive caster) giving straight line stability at speed. But the greater the caster, the greater the steering effort that is required, so a tradeoff is required. Race cars usually benefit from about 5 degrees of positive caster. See these additional articles steering geometry more steering geometry
If you are still interested in more, do a search on Ackerman effect and bump steer to read about how static steering settings change when steering iputs are made or when one tire goes over a bump while turning.
For the price of a couple of professional alignments, you can buy the tools to do your own. For less than half that, read someone elses plan on how you can make your own tools.
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