Camber Change

The cambers will change as the car dives and rolls as it enters and negotiates a turn. True camber change is a combination of both chassis dive and chassis roll. Gone are the days when we would jack up the wheel and measure how many degrees the camber changed in each inch of bump. Those numbers really don't tell us anything. That is only part of the answer. Chassis roll has an affect that adds or subtracts from what dive does. So, what we really need to know is what the dynamic camber ends up at after the car dives and rolls, just like it does in the turns.

The left front always loses a lot of camber, so we need to allow for that in setting the amount of static camber. Generally, if we end up with between 1/2 to 1 degree of positive camber at the LF wheel after the car dives and rolls, then that tire will have the dynamic camber that it needs.

The RF camber change is a little different. We can design our car so that the RF camber doesn't change after dive and roll with the more conventional setups. This is actually exactly what that tire wants for most short track applications. The reason for this is that as we enter the turn, the RF tire takes a set fairly quickly. If the camber continues to change after that initial set, then the tire will give up traction and the car will usually push.

The more modern soft spring setups where we run on bump stops will do basically what the conventional setups have done in years past. Once the car is on the bumps, the cambers are basically fixed and don't change much around the entire racetrack. That lack of change is one of the positive aspects of the soft spring setups that we have seen.

Still, with any setup, the cambers will change from where they are at normal, static ride height. The right upper control arm angle mostly controls the amount of RF camber change, so we try to work with that control arm angle and once we have the minimum amount of camber change, we leave that angle alone as we further design our front end for Moment Center location.

Spindle Height

Spindle height affects the amount of camber change at each wheel too. The taller the spindle, the less camber change will occur. Trends that have taken place in the past have resulted in greater camber change due to the use of shorter spindles. That trend is in the reverse mode now as car builders move toward using taller spindles.

Measuring Camber Change

We can measure camber change by several different methods. In the shop, we can set the chassis ride heights just as they would be at mid-turn on the racetrack and then directly measure the camber at each wheel. To do this, we will need to know the shock travel at mid-turn, which is very hard to estimate.

If we look at the shock travel indicators on the shaft of the shock, it always tells us total shock travel which includes braking, going over bumps, banking changes such as exiting the racetrack and driving down onto the apron (this could be quite a lot of LF shock travel at some high banked racetracks) or something as simple as steering the car back and forth to warm the tires before running hot laps.

Sometimes it is sufficient to place the car to where the front valance looks similar to what it is on the racetrack at mid-turn. The team can remove the springs, place spacers under the crossmember and adjust the height until the car looks the same and then measure the camber. When using bumpstops or bump rubbers, you can lower the car onto those and the attitude will be close to what happens on the track.

Conclusion

Remember that caster settings are mostly adjusted for driver preference and comfort and are relative to the design of the track, and camber settings are important so that the front end will have the maximum amount of footprint and traction to use to turn the car at mid-turn. Many of our problems related to a car that won't turn well come from incorrect camber settings and camber change problems.

Often, a car that has a serious push can be helped by analyzing and adjusting the static camber as well as knowing the camber change amounts. For dirt cars, taking tire temperatures may not be feasible, but measuring tire wear can have the same effect as temperatures. The more wear, probably the more temperature that part of the tire experiences. Even wear translates to more even tire temperatures and the best camber settings.

Gone are the days when we would jack up the wheel and measure how many degrees the camber changed in each inch of bump

Remember that caster settings are mostly adjusted for driver preference and comfort and are relative to the design of the track, and camber settings are important so that the front end will have the maximum amount of footprint and traction to use to turn the car at mid-turn

SOURCE
Intercomp
North Minneapolis
MN
800-328-3336
www.intercomp-racing.com