|Caster, Camber, Toe, Part II: CAMBER
Camber is defined by the angle of the vertical line through the center of the wheel and tire relative to a straight line, perpendicular to the ground (on the flat). If the top of the tire is leaning away from centerline of the car you have positive camber; if it's leaning in toward the centerline you have negative camber.
Too much or too little camber produces uneven tire wear, because it has a significant effect on how the tire meets the road surface. Any modifications you make in camber will affect the shape and size of the contact patch. You can correct tire wear problems (as well as other suspension or ride issues) and increase your grip in the corners by adjusting the camber - giving the suspension negative camber in the setup, if you know that it loses camber in the corners for example. (Preset negative camber will flatten out when it is neutralized by positive camber in cornering.)
However, you can cause problems by trying to preset camber without taking into consideration all the other things going on in the suspension. "Camber" has become something of a quick-fix - often without understanding what's actually going on in the suspension.
For example, if you're using 1400-lb. springs, and then you set the car up with lots of negative camber for the corners, you'll find you're still getting significant tire wear, because the springs simply won't let the body roll - and won't stand the tires up in the corners. You need to take out some camber to get the face of the tread back down on the road.
MacPherson Struts Camber control was the reason MacPherson designed the MacPherson strut. When a wheel hit a bump it would swing up and in, towards the centerline (negative camber). To counteract this increased negative camber over bumps, race cars were set up with the tire tops are angled out - with severe positive camber, sometimes to ridiculous extremes. MacPherson designed his strut to deal with this uncontrolled camber gain (increased negative camber) by getting the wheel to go up and down, rather than arcing, over bumps.
Struts vs, A-arms But the problem with struts even now, in comparison to A-arm (wishbone) suspensions, is the upper mounting point is fixed and because it can't move relative to the body, the body roll tends to push the top of the strut and therefore the top of the tire out, causing positive. Heavier springs will reduce the body roll. But, as in the example, if you then also dial in lots of negative camber to counteract the effect, the car will carry tilted-in tires through the corner, as well as on the straight, and you'll have even more uneven tire wear.
The advantage to a double A-arm or wishbone suspension is that you can dial-in positive or negative camber to keep the tire face flat when the body rolls.
Camber Adjustment Although we will cover the adjustment of caster, camber and toe in a later University Topic, camber is adjusted by changing the position of the control arms; or, in strut cars, with camber plates. The plates have bolt slots that allow you to change the angles of the struts to change the camber by moving the top of the strut in or out. Many cars now (VW and Porsche were among the first) have two-bolt flange mounts for the struts that accomplish the same result.
Next time we will look at Toe - and examine what to look for when you're trying to determine if a tire wear problem is being caused by the need for camber or toe adjustment. Later we will get into adjusting all of these.
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