Proper 18" tire size for 10" rear wheels??

[ktee]

Hey there,

I ordered 18" Italian replicas (8" front/10" rear) for my summer tire set-up and installed winter tires on my factory 18s. I was planning on installing the factory rubber (265/40/18) on the new wheels, but my installer told me that those tires are not wide enough for the 10 inch rear rims. When I look at Tirerack, I don't see any 275 or 285 18s that are Porsche rated.

Need some help - thoughts anyone??

Thanks,

Steve

[JackTs2K]

Originally Posted by ktee

Hey there,

I ordered 18" Italian replicas (8" front/10" rear) for my summer tire set-up and installed winter tires on my factory 18s. I was planning on installing the factory rubber (265/40/18) on the new wheels, but my installer told me that those tires are not wide enough for the 10 inch rear rims. When I look at Tirerack, I don't see any 275 or 285 18s that are Porsche rated.

Need some help - thoughts anyone??

Thanks,

Steve

I have 18" Carrera 3 wheels on my 07. The rears are 10" wide like yours. I'm using the 265/40ZR18 PS2s. The tires haven't fallen off wheels yet.

[TriGem2k]

Ktee

Is this for a 986 or 987?

You can either run a 265/35/18 which WILL fit on a 10" wheel. The tire will just look a little bit stretched.

I personally run a 285/30/18 on my 10" rear wheels. This is also a factory Porsche tire size.

What is the offset of your wheels? Ultimately this will determin what size tire you can run.

[ktee]

The car is a 987 and the offset is 47. Will the 285/30/18 fit that offset?

[racer_d]

I thought it a bit funny.. Worry about "Porsche rated" tires on your "Italian replicas".

A 275 or 285 would be a preferred width for a 10" wide rim. Porsche doesn't have a prefered tire because they don't equip (base or option) a 10" rear wheel on the Boxster. Now, depending on any mods to the car, in particular the suspension, this is where you could have fitment problems. But, they should work ok.

[husker boxster]

I used 275/35/18s on the 10" 47mm rears on my old 01S. This size really filled out the wheel nicely. (BTW, the tires are for sale in the classifieds - shameless plug.) Your 265 will work but it may be a stretch for that wheel. There won't be much tire sidewall protection of the wheel lip. I went with 275/35 because there were more choices available in that size that were reasonably priced. There's quite a price jump when you go to 285/30, mostly because there are fewer manufacturers.

Also, according to the handy-dandy wheel offset calculator, going from a 9.5" 43mm wheel to a 10" 47mm wheel will move it inward by 10mm (approx 1/4"). That's a healthy move. Might want to see if there are going to be clearance issues. Some spacers may be required. On a 986 it's an 8mm move (9", 52 to 10", 47) and there are issues with the e-brake cable. Don't know what might be lurking on a 987.

Good luck and enjoy.