Michellin Supersport PSS correct size

FD3S · Post by **FD3S** » Wed Oct 20, 2021 3:22 pm

Hello I would like to ask a quick question. What is the right size for BMW Z4M for Michelin Supersport with standard wheels?
255/40/18
225/45/18

or

255/45/18
225/45/18

???

buzyg · Post by **buzyg** » Wed Oct 20, 2021 3:28 pm

The first option is what I have always fitted.

mmm-five · Post by **mmm-five** » Wed Oct 20, 2021 5:34 pm

First option is correct - which keeps the front to rear tyre ratio the same despite the wider rear tyre.

If you did the 2nd option, you'd end up with a rear tyre profile that was about 1cm taller than the front:

225/45r18 = 660mm diameter
255/40r18 = 661mm diameter
255/45r18 = 687mm diameter

Another option is a:

265/40r18 = 669mm diameter

...which is what I had fitted as the 255/40 was not available originally, and I just stuck with it - but you may get a slight rubbing on hard compressions (I only get it in 2 places on the 'Ring, but that's with aftermarket suspension on hard settings).

Mr Tidy · Post by **Mr Tidy** » Wed Oct 20, 2021 8:42 pm

Yes, the first option is factory sizes.

But when I bought new tyres in April I went with your 2nd option for a bit more sidewall and haven't had any issues - plus they fill the wheelarches a bit more!

FD3S · Post by **FD3S** » Wed Oct 20, 2021 11:17 pm

Perfect. Thank you guys for your immediate response.

Argenta · Post by **Argenta** » Thu Oct 21, 2021 12:31 pm

I do believe the answer was much closer than this forum; either on the note by your driver door or in the owners manual.

mmm-five · Post by **mmm-five** » Thu Oct 21, 2021 3:37 pm

Argenta wrote: ↑Thu Oct 21, 2021 12:31 pm I do believe the answer was much closer than this forum; either on the note by your driver door or in the owners manual.

Assuming the OP was with the car!

The internet is with you 90% of the time even when you're in another county/country without the car!

Argenta · Post by **Argenta** » Fri Oct 22, 2021 11:26 am

Hehe ok true in case

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