My front PP SO-2s are on the way out pretty soon. Right now, I've got 225/45-17 and 245/40-17 on 7.5 & 8.5 rims respectively. The only upgrades to the car are Koni SA inserts, x-brace and E46/Z3 RSMs. I have not yet tracked the car, but may in the future. I ran 30F/35R psi, but changed that to 35/35 to try to dial out some understeer. Konis are set at almost full soft front and rears are about 1/2 way to stiff.

Without changing wheels, do you think that running 235/40-17 up front will help reduce understeer even noticably? In most steady state cornering on ramps and such, I definitely feel that the front is about to push unless I gas it a bit.

I'm thinking that when the rears wear out, I'll go 235/40-17 all around on the staggered rims. This is what the Euro setup is no?

Also, has anyone noticed poorer turn-in characteristics with 235/40-17 up front as opposed to 225/45-17?

Please post your opinions for those who have been there.

TIA!

235/40/17 on 7.5/8.5 whels works quite well. This is the same way that the 95 LTWs came fom the factory. It will definatly help get rid of some understeer, but I would consider looking for 2 additional 8.5 wheels and running those with 235/40/17 on all 4 corners.

I've never known the reason for this. . . why did bmw go with 235's on staggered wheels? Brian, any thoughts?

It does seem weird to me a full 1" difference in wheel width, yet the same tire size. The ideal wheel width for most 235/40 tires would be right in the middle at 8" from what I've seen on most tire manufacturer sites. But, if BMW considered it, there must have been a reason.

I just worry that the larger front will be less sharp in turn-in than the 225, although perhaps providing more ultimate front grip. I assume that the 235/40 on 8.5" in the rear doesn't appear too 'stretched', although I've yet to see it.

Naw, rolling diameter, and hence effective sidewall height, are smaller for 235/40's vs. 225/45's.