Front tire cupping

[DeansBimmer]

I haven't been stumped like this in a while. My front tires are scalloping on the inside, on both driver and passenger sides. The whole front end is pretty new, I've rebuilt it completely over the last few thousand miles. I cannot find anything worn out. In picking up the car and trying to jar the front wheel assembly, it is rock solid, nothing moves.

In about 5k miles, the new Eagle F1 front tires have been worn down to less than 1/16" tread in the scalloped area! The toe is adjusted as close to zero as possible, but it feels as though it may have a bit of toe out. The car pulls straight ahead with no shimmies or vibrations at any speed. I even paid $75 for a professional computer alignment, but that has seemed to accelerate the wear.

You can clearly see the massive wear in these shots. Any ideas? :eyecrazy

http://img.villagephotos.com/p/2003-11/511157/XRVLF-_MG_8951.JPG

http://img.villagephotos.com/p/2003-11/511157/PPYIS-_MG_8952.JPG

[slipstream]

That shock doesn't look stock so what else have you done to the suspension? Do you have camber plates? What's the angle? How good was they tech who did the alignment? Do they work on modified BMW's alot?

[DeansBimmer]

GC springs, 450lb front.
Koni Yellow Adjustable
Vorschlag Camber plates (need to measure angle) I suspect about 2 degrees
M3 CABs and sways

Bushings, tie-rods, and other balljoints are fresh.

The shop I went to has a good reputation and "works on Ferarri's", but I don't think the know about modified BMW's, as the f*cked up my brother's e30 aligment.

I went back in and readjusted it to as close to 0 degrees toe as possible with some toe plates and tape measures.

Right now I'm leaning towards worn struts. The ride doesn't really indicate them being an issue, but I don't know what else it could be.

[slipstream]

I'd try to find a good shop that has experience with racing BMW's. They will know how to setup the car for how you want it, and they'll know what works and what doesn't. Unless the tech who ran the alignment machine was experienced with aftermarket setups they will go with what the computer says is supposed to be correct, for a stock setup. When they did the alignment did they give you a printout of the before and after settings?

[DeansBimmer]

No. the shop didn't give me a printout. I told them to set it at zero, but they obviously didn't.

I don't know of any BMW racing shops in my area that would have the expertise in suspension and frankly am pretty low on funds right now, but that sure sounds like a good idea.

[marlinspike]

Is 0 toe the right spec? I imagine with stock rubber bushings it ought to run a little toe-in. I'd also wonder what the total camber is up front.

[DeansBimmer]

I requested 0 toe. They wanted to put in .03 degrees of toe in. Running 0 is quite reasonable for modified setups. There is 2.5 degrees of negative camber. I removed the shocks and found no resistance in its compression, plus the gas has mixed with the oil. They're blown.

I believe the spring rate is too high for the shock, and will probably be sending them to Koni to be revalved.

[Critter7r]

So there's your answer...

[TyKBlue82]

I have only seen cupping like that caused by blown struts/shocks...makes sense.