checking rear camber

[CSatterley]

I was wondering if people change/check camber by adjusting the shock or adjusting links from the trailing arms to the shock/zero roll. My total camber is good but is uneven from one side compared to the other. Is this scrubbing straight line speed? The difference from the right side to the left side is about 1-2 degrees.

[Larry Bradley]

The links should be the same length, and you adjust with the spring/shock length.

If you have a difference side to side you need to check it on a level surface.

You should be able to get camber the same on each side without much screwing around.

Larry

[hardingfv32-1]

It really doesn't matter. One possibility if the two sides are not equal is a twisted frame or the beam is not mounted/positioned properly to the frame.

Brian

[DanRemmers]

Now wait a minute. If it's a zero roll, then unequal links, tilted front beam, or a twisted frame would not change the rear camber much at all, would it? Please correct me if I'm wrong. (Z-bar is a different animal)

If the camber really is that different between the two rear tires, the zero roll may be binding. Jack up the gearbox and see if the wheels move freely up and down.

[CSatterley]

There is no binding in the zero roll when I jack it up, but when I check camber on level ground there is big differece from side to side and i notice I'm getting uneven tire where on the side that has more camber. The car actually handles really well, so I'm a little reluctant to change anything. If I'm losing straight line speed though I would change it and I it seems I am, but then again I don't have one of the MONSTER manifolds or whatever : ) I need the excuse so i'm not buying one until I run out of other excuses.

[remmers]

Do you have the same result with a different gearbox? where do you check your camber from? I personally check it from the center of the axle tube with a digital gauge my dad picked up at the runoffs one year. If you're checking from the wheel, could there possibly be a bend somewhere in the wheel or tire that causes your readings to be out of whack. I think you would notice a vibration if there's a bend. Only other thing I can think of is if your transaxle is twisted longitudinally. That would cause you to have odd readings because the geometry is all out of whack. you'd be able to check that by putting the car on a level surface and checking the height from the ground to the bottom of the axle at the point it connects to the trans. If they're different, you've got a twist in either the frame or the trans mounts, which personally I would want resolved, but I don't think it would be completely necessary if the car's already handling well enough.

[CSatterley]

I do check it from the wheel, but they are pretty much new and have never been bent. It is a Caracal and the front beam is very high on the frame so I'm not sure if that make much of a difference with a zero or not, but it isn't bent. I've had a couple different tranny's on the car with the same situation. Maybe I will look into the mounting points on the frame to try to find the reason.

[remmers]

yeah, the front beam should have no bearing on the rear camber.

[hardingfv32-1]

You are correct, the beam mounting has nothing to do with the rear camber in the normal situation. I was thinking more about the car not setting flat to the ground. I'm not sure how you would get unequal rear camber if all the links are the same and the car is level to the ground. Is the transmission centered in relation to the rockers and control arm pickups?

Brian

[DanRemmers]

Take a good picture of the car from the rear with the body off (hi res picture, square with the viewfinder frame, looking straight up the shift linkage, maybe hang a couple plumb lines near the wheels). We should be able to SEE what's wrong.

[jpetillo]

Anything that causes the transmission to rotate from perfectly flat and centered will cause the rear cambers to be different. This is just geometry and has to do with the swing arms and their mounting points in the transmission. This is independent of the rear suspension geometry and has nothing to do with zero roll resistance or anything else. A non zero roll resistance rear suspension can cause this or help prevent it, but a zero roll resistance rear suspension shouldn't be able to unless it's binding or has significantly different arm lengths on each side.

So, assuming that the transmission is square in the frame, then anything that causes the frame to roll can cause different cambers in the rear. This could be from the engine/transmission not being mounted square (unprobable), twisted frame, the rear suspension binding perhaps on one side or different arm lengths, unbalance of weight (may take a lot of unbalanced weight), or the front beam being off somehow.

I'd say that the front beam is the most likely suspect since it can cause/prevent roll, and that's the first place I'd look.

If the spring on the front end is not providing the same force from side to side, you have a twist in your anti-roll bar, or suspension movement binding on one side in the front, this would roll the car if you jacked up the front (in the center) and then set it down, causing the rear camber change.

I believe this is right and I hope it helps.

John

[brian]

Jim makes some great points and it makes a lot of sense. I always take all the adjustment out of the shocks when setting camber in the shop to eliminate any sticking and friction. Track side is another matter. I like to acheive desired camber with the least amount of spring then use the shocks to tune the car. Once at the track if I want to change camber, I do so with the push rods and readjust the droop. Moving the spring is good for big adjustments but I like to keep the spring perch constant as a base line. If the car continually gains camber(more negative) during a session I will add a bit of spring to compensate. If the car still sags, it may be time for a spring or better cooling for the spring and shock. Many a spring has met it's death from excessive heat.

[problemchild]

I would check that the droop limiting device is not preloading the rear suspension so as to simulate rotatation of the tranny slightly as if it is not squarely mounted. Many Caracal, Adams, Mysterian type cars that use a bump rubber on the upright on one side are prone to odd preloads when the car is sitting driverless. While I don't like this situation (and try to rectify it) it rarely affects the suspension when movingthrough the on-track dynamics. I have seen championship-winning cars that would cock the rear suspension to one side when jacked off the ground.
Probably not anything to worry about but you won't know that until you identify the cause.