need help with new tires on 03 roadie with oem 18's

[DannyZ]

from the dealer it came with 225 40 18 in the fronts and 255 35 18 in the rears (according to tirrack.com) I bought the car used and it came with 225/40/18 in the front and 245/40/18 in the back... it's definatly time for some new tires and I don't know what size to get.

I have a 2003 sport suspension z4 roadster with the 3.0i engine and the oem 18 " wheels the car does not have runflats on it now and I will not be putting runflats on it.

I was hoping to put one size bigger in the front and rear to hopefully get me a little more clearance and ride comfort(I know it would be a small difference , but i'll take waht i can get)

what are the different sizes I can get and combos that you guys have tried and worked out...what should I stay away from, etc.

SHOULD I JUST GO BACK TO THE STOCK SIZES? STAY WITH THE SIZES I HAVE NOW? OR...?

PLEASE HELP TIME SENSITIVE...

[zuendi]

Hi there,
It depends on the wheel width, what do you have 18" x ?? front and 18" x ?? rear?
Zuendi

[Reach]

Assuming you have the stock sport wheels (the ellipsoid ones) I'd go back to the stock sizes.

[DannyZ]

thanks, i do have the stock 18's what are the benifits disadvantages of changing them and to what size?

[zuendi]

Because I don't know the stock size of the 18" I can just tell you if you have
18x8.5" Front & 18x9.5" Rear you can go for a combination of 225/40-18 Front & or 255/35-18 rear or 235/40-18 Front & 265/35-18 Rear.
According to my information the mentioned size 225/40/18 in the front and 245/40/18 in the back is not applicable I think. The problem is the tire hight 35 is correct
(40 in the rear?) BR Zuendi