Determining correct front camber gain?

[69427]

After several track days with some reasonably soft tires (Hoosiers) I've noticed that I'm wearing the inside of the tread more than the outside. I have minimal static negative camber on the fronts so I'm thinking I have too much camber gain. Seems like a little less camber gain might be the answer, but it would also help keep the tires more vertical during hard braking (due to any nose dive issues), so that should be two improvements from one change. I'm thinking that raising the UCA inner pivots upward should help out. The ride height is currently a little higher than this old picture, but it does show some angle on the upper control arms.



The UCA mounts are removable/unboltable from the frame (in the event that I wanted to alter the front geometry), but in the mean time I was thinking about making some spacers to raise the mounts up a bit to see what height gets the geometry where I want it. I can then just weld up some new UCA mounts when time permits and swap them in.

I don't know how to "calculate" an ideal virtual swingarm length for the suspension, so it seems that some trial and error adjustment is necessary (correct me if I'm wrong) to get the camber gain correct. Make sense, or am I missing anything?

 

[phantomjock]

The yellow is a quick and dirty VSA. A bit more difficult with the body all on.


And, a "fancier diagram:




Cheers - Jim

 

[BBShark]

I don't think there is an ideal virtual swingarm length.

Does your car tend to under/oversteer?

 

[Twin_Turbo]

Or...your car has too much roll stiffness (or too much camber gain for little body roll). Easier than modifying the suspension, loosen the sway bar and check if it mogrates the wear pattern to the outside.

 

[SuperBuickGuy]

A lot of ideas, but have you filmed the car doing hard braking, cornering or both? Any of the ideas (or none) could the be the cause of your issue - but maybe a day of autocross filmed with a GoPro would give you a better idea of what is wrong and what needs to be fixed.

 

[racervette69]

Could you post a picture of the wear?

 

[redvetracr]

try a infrared gun to measure tire temps, but find someone to shoot the tires hot right when you come off the track, otherwise by the time you get unstrapped and get the helmet off to do it yourself you won`t get accurate readings ...worked for me!

 

[69427]

Okay, several questions/suggestions.

Handling: The car is remarkedly balanced. I attribute that more to the inherent quality of the C4 suspension geometry than to the guy who put the suspension in. I copied the spring rates I was running previously with the stock C3 suspension pieces, and it's nice having a rear suspension that doesn't keep trying to bite me at inconvenient times.

Too much roll stiffness: I don't know how to quantify that. I assume my car still has some roll in the corners, but I don't have any video to quantify it. I am curious if perhaps I'm getting too much camber change under hard braking, and causing the inside tread to do most of the braking work (just speculation at this point).

Checking tire temps: Makes perfect technical sense but I usually end up at the track solo, so there's rarely anyone to help me get the temps taken quickly.

Tire pics: I don't have any presently, but I'll grab the camera and take a photo to show the wear.


I think I'll try raising the upper a-arm pivot height a touch and see how the car feels in cornering and braking. It shouldn't take much effort and material to do this change.