Tire size on Carrera III wheels - 18x8/18x10

[FoFoJoe]

For reference, the Carrera III's I run are ET57 up front, ET58 in the rear. I use a 15mm spacer in the rear, and will probably grab a 3-5mm spacer for the front.

8Jx18 ET57 (P/N 99736213600)
10Jx18 ET58 (P/N 99736214001)

I am on Eibach lowering springs, bringing me down about 1.5" if I had to guess. No rubbing as is.

From my math the 275's won't rub, but they will be here next week so we'll see.

[FoFoJoe]

Out of curiosity I ran the offset calculator to compare our set ups.

Our rear set up is identical when you aren't running the spacer (not accounting for wheel width, but with matched tires offset calculators read them as the same width.)
If I had to guess, your set up could be a tad thinner at the fender because your tire is a tiny bit more stretched compared to mine.

58mm stock -15mm spacer (43mm effective) on my wheels.
43mm stock, no spacer for yours.

With the spacer on your rear, you push to 38mm. So by that math, the extra couple mm should let the 275 tire fit without issue on my car.


Here are the fronts.



You're 7mm out compared to mine, with the same width wheel (8inch). I am currently running a 225 tire. With a 7mm spacer and a 235 tire, by these numbers I shouldn't rub. Especially considering you ran your setup for Auto-X, which in my mind would push the suspension to rub if the chance was there.

Main difference is our ride height. I don't know your suspension set up, but I am about 1.5inch lowered so maybe a 3-5mm spacer would be a better choice for me.

So your data was very helpful. Do you have any pictures of your Boxster with the auto-x wheel set up on by chance?