Mate and his crazy winter tyre choice.

[Backtobasics]

Long story short. My mate has bought 225/40/r18 winters. He's currently got 255/35/18 fitted! I believe he was high on crack and fet when he ordered them. I've told him there is no way he can use them, just want to check I'm right.

[V88Dicky]

They should be fine. As long as they're going on narrower rims?

[Mercury00]

Forget that, I was looking at the wrong size

http://www.1010tires.com/Tools/Tire-Size-Calculato...

[E30M3SE]

1mm difference in overall diameter between those two sizes, so no dramas there as long as they aren't too stretched on the rims, assuming he's using the same rims.

[jagracer]

Why can't he use them?

[unpc]

OMG, OMG that's so crazy. Something might happen to something somewhere.

[B'stard Child]

Backtobasics said:

Long story short. My mate has bought 225/40/r18 winters. He's currently got 255/35/18 fitted! I believe he was high on crack and fet when he ordered them. I've told him there is no way he can use them, just want to check I'm right.

Unless they were already stretched on a wide rim I would have said they'd be ok

[Backtobasics]

Glad to be proved wrong, so he's ok?

[Red 5]

My summer rear tyres are 255/35/18

My winter rear tyres are 225/40/18 on 8.5"

My car has 400bhp, but is yet to try to kill me on either of the above sizes.

What do you think the problem might be?

[Backtobasics]

I was always told to stick with the same tyre size that the manufacturer recommends.

[Matttracker]

It's not much at all. It's a perfectly ok choice as long as it's not a 10" rear.

[Matttracker]

This is a 9.5 all brands are slightly different but it's not bad at all

[Leptons]

It's the norm to go narrower on your winters...

[Hark]

I ran 225 on the rear of a Z4m which is a similar change. Was decent in the snow to be honest.

[TA14]

Backtobasics said:

I was always told to stick with the same tyre size that the manufacturer recommends.

Best to go back to basics then. Nominally a tyre width size will be the wheel width plus an inch plus a few mm to convert it to a metric size. There are many exceptions done for many reasons. As stated above if the original 255 was a stretch (unlikely in the case of an OEM) then it won't be OK; in most other cases it should be OK

[BritishRacinGrin]

Backtobasics said:

Glad to be proved wrong, so he's ok?

Yes, just as soon as he comes down from the crack and ket.

[Mr E]

[jon-]

Just make sure he tells his insurance company as changing sizes is a modification.

[MogulBoy]

225/45's vs 255/40's on an 8.5J 17" Boxster rim is a 'Porsche approved' choice for winters on the 986 and is recommended if you need/want to use chains but equally, sticking with the same 255/40 profile is also 'approved'.



More here.. http://goo.gl/9u0fNW

[Jonjo91]

jon- said:

Just make sure he tells his insurance company as changing sizes is a modification.

Not this again....