Tire Recommendation for 18x8 Square?

[Dubbedown]

Hi everyone

I recently purchased OZ Ultraleggeras in 18x8 square fitment for my Z4 coupe (non-M). I'm going to purchase new tires and would like to know the optimal fitment. Should I run same size tires on all 4 corners or put wider tires on the rear despite the square wheel setup?

The car is only driven on weekends but I will do my first HPDE and auto-x next month and hope to do a few more during the course of the year.

Thanks in advance!

[EpDarks]

I have 225/40 on my 18x8 square, but I would run 235/40 or 245/40 depending on the tire.

Yes, run the same size tires all around.

[Dubbedown]

i was thinking the same. ideally i'd like to run 235/40 but with a 40mm offset i'm rubbing the liners on the front. but 225 all around seems a bit narrow? as of now, plan on going with the hakook v12s

[EpDarks]

Buy some 5 or 10mm spacers for the front and your rubbing is gone...

225 is indeed narrow, but for street driving it should be enough.

Since you mentioned track events I would go with a 235 Dunlop Direzza Star Spec, but I'm biased because mine are in the mail :)

[Dubbedown]

Buy some 5 or 10mm spacers for the front and your rubbing is gone...

225 is indeed narrow, but for street driving it should be enough.

Since you mentioned track events I would go with a 235 Dunlop Direzza Star Spec, but I'm biased because mine are in the mail :)

But If I'm rubbing on the outside, not suspension parts but on the outer part of the liner where it meets the fender, isn't spacers just going to make it worse?

[EpDarks]

You're rubbing on the outside w/ 235/40s? I don't know anything about Z4 fitment but that does not seem right to me.

[Dubbedown]

You're rubbing on the outside w/ 235/40s? I don't know anything about Z4 fitment but that does not seem right to me.

correct 18x8 et40, stock fitment is 18x8, et47 with a 225/40 tire.

it might not be the outer edge, i'll have to check again. maybe you're right and it's hitting the the middle of the liner, which i guess in that case implies it's the inner edge of the tire making contact which in that case a spacer would help.

[EpDarks]

I gotcha, did you get any feedback on the Z4 boards? I'm sure they've been through this...

GL

[Dubbedown]

actually i've dug through alot of posts but nothing really. if u want the whole history, at one point i was running 18x8.5 et 35 with 235/40 and that definitely rubbed on the outside. in fact, the plastic under my sidemarkers almost became non-existent. i ultimately decided to put on new liners after i got my new wheels thinking the less aggressive width/offset would work (keeping the same tire). on my drive home though, i definitely heard it rubbing and after i parked, i stuck my hand behind the liner to feel some plastic "shavings" off the liner. so i came to the conclusion it was really the tires, the overall diameter of a 235/40 vs a 225/40 is about 1/3rd of an inch.

[EpDarks]

Well in short you'll probably need a lower offset wheel to run more rubber.

I believe some wheels can be shaved to decease the offset? Or maybe OZ can source you a pair of +47 18x8? Do you think a fender roll would help?

[Dubbedown]

Well in short you'll probably need a lower offset wheel to run more rubber.

I believe some wheels can be shaved to decease the offset? Or maybe OZ can source you a pair of +47 18x8? Do you think a fender roll would help?

eh, i'd rather run 225s than roll my fenders but appreciate all the feedback upto now. gotta think this through.