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[Oofie]

My brother just got a 135i which is replacing his Z4. We autocross his Z4 with a set of Kosei 17s et40 8.5" wrapped in Dunlop Direzza SS 255/40/17. So now we have a dilemma.

From what I've read here, there's no way we can fit this set on the car without a lot of neg camber/fender rolling. Problem is we want to keep the car bone stock except for the wheel/tire combo we have.

I've read that we can fit 235's all the way around, but I'm still looking for other options. Is there a set of wheels that we can use so we can fit 255s all around? If we decide on just using the Kosei with 235's, is there be a big difference between 235/45/17 and 235/40/17?

Thanks!

[fboutlaw]

I've played around a lot with tire fit and finally have my car setup with a 255/275 setup.

With a stock suspension, you can only fit 235 up front. You can always downgrade the rears to 235 if you want to go square, but your grip is going to suck.

The problem here is front fitment. From my experience, here's what you can fit.
235 | stock
245 | -1 deg camber
255 | -2 deg camber - have to shave down the flashing where bumper meets front quarter

The correct offset for the front is +45. It's incredibly close so based on the bead protector on the tire, you may need a 3mm spacer. Also, Vorshlaq camber plates are the only ones that allow the camber to fit 255's.

In the rear, the correct offset is +62. It's hard to find wheels in this fit, but the reward is being able to fit up to 275's with no rubbing.

Note: the fitments I listed are for 18" wheels. You may need slightly more offset on a 17" to clear the strut tube.

[Dackelone]

Every car is slightly different in build. Why not jus TRY to mount your square setup and see IF it works?

[Lubo]

Originally Posted by Dackelone

Every car is slightly different in build. Why not jus TRY to mount your square setup and see IF it works?

I drove about 30 miles with identical tires wheel offsets. You will need to dial max camber in the rear and you may still rub a bit. I went with -2.0* and slight roll. There is no way to fit 255 up front without camber. I am running -2.5* with the plates. Here are some pictures of the tires with stock alignment.

[Dackelone]

^^part of the problem is no two tires measure the same widths - even IF they are the same number size. What I mean is say a 255 wide Michelin will not be the same size(real life measured in mm wide) as a 255 Dunlap.

[Lubo]

Originally Posted by Dackelone

^^part of the problem is no two tires measure the same widths - even IF they are the same number size. What I mean is say a 255 wide Michelin will not be the same size(real life measured in mm wide) as a 255 Dunlap.

yes but OP has same exact tire and size as do I. Even though we have 2 different wheels they are the same size and offset.

[Oofie]

Originally Posted by Lubo

yes but OP has same exact tire and size as do I. Even though we have 2 different wheels they are the same size and offset.

Thanks Lubo! Just the answer I was looking for

Looks like we might have to go 235's all the way around, unless we install camber plates.

[Oofie]

Originally Posted by Dackelone

Every car is slightly different in build. Why not jus TRY to mount your square setup and see IF it works?

We mounted the set yesterday. Looks like the rear might be ok with some more camber, but we won't risk it as we would like to run a square setup, so it might be 235/45/17 for now. Wheels will be painted black next month before our next autocross.