Tire fitment for stock 18's

[purdyawesome]

So, can someone tell me what tire sizes will fit on the stock front and rear 18's without noticeable stretching? Without rubbing? I'm looking for winter tires and there's nothing available in the stock sizes. I have seen that the 265x40x18 will easily fit the rear wheel - albeit with some stretch. Noticeable stretch? I have no idea... But, what about going the other way??? Could a 285x35x18 fit? even wider than this? and how does the aspect ratio alter the equation? if someone could list the tires sizes - rather than pointing to specific tires - in order of most to least ideal in terms of relation to OEM fit for both the front and rear, that would be an enormous help in the search for a decent snow tire. it seems that tire rack isn't a great resource because they only list exact approved and tested fitments for an oem replacement -this and, they won't display tires that fit front or rear separately in the search results so I feel that it hides a few potential solutions.

[Maxis]

265x40x18 will easily fit the rear wheel - albeit with some stretch. Noticeable stretch?
( Litlle stretch with michelin, lesser stretch with Pirelli....)

rim width --------Min ----------ideal------------max

9,0 Inch----235 mm----245 of 255 mm----265 mm

10,0 Inch---255 mm----265 of 275 mm----285 mm

Hope this helps,,

[purdyawesome]

Originally Posted by Mere

265x40x18 will easily fit the rear wheel - albeit with some stretch. Noticeable stretch?
( Litlle stretch with michelin, lesser stretch with Pirelli....)

rim width --------Min ----------ideal------------max

9,0 Inch----235 mm----245 of 255 mm----265 mm

10,0 Inch---255 mm----265 of 275 mm----285 mm

Hope this helps,,

Helps a lot! Thank you. One more quick question though- does stepping down the abstract ratio to 35 in order to step up the width for more availability work? Or would it throw off the drivetrain? Speedo, traction control, etc... There seem to be a few more options for snow tires available in 285x35x18...

[Maxis]

you really should be thinking about downsizing your winter set, if you can'.

The benefits are quite clear. A smaller and narrower tire has better grip and performance in snow or ice.

This is both because the smaller tire cuts through snow more effectively, and because the weight of the car is pressing on a more focused set of contact patches.

[purdyawesome]

Originally Posted by Mere

you really should be thinking about downsizing your winter set, if you can'.

The benefits are quite clear. A smaller and narrower tire has better grip and performance in snow or ice.

This is both because the smaller tire cuts through snow more effectively, and because the weight of the car is pressing on a more focused set of contact patches.

Okay. Thanks. So long as the 265x40x18's don't look ridiculous on the stock 18's I just picked up, I think I'll go that route. I would have thought someone would have released an OEM sized set for winter by now!

[mkoesel]

Originally Posted by purdyawesome

Helps a lot! Thank you. One more quick question though- does stepping down the abstract ratio to 35 in order to step up the width for more availability work? Or would it throw off the drivetrain? Speedo, traction control, etc... There seem to be a few more options for snow tires available in 285x35x18...

A 285/35-18 would work fine, yes. Tire rolling diameter will be 25.9". By comparison, the stock summer rear 275/40-18 has a rolling diameter of 26.7". But the OEM winter setup has a 255/40-18 rear which is only 26" in diameter, so you'd only be down a tenth of an inch from there.

Now, whether you actually want to be sizing up to 285mm width for a snow tire is another question.

Originally Posted by Mere

you really should be thinking about downsizing your winter set, if you can'.

The benefits are quite clear...

I don't disagree, although 255mm (the recommended winter tire width by BMW) would seem arbitrary if narrower is better. After all, we could run the car on 245mm, 235mm, or even 225mm.

Originally Posted by purdyawesome

Okay. Thanks. So long as the 265x40x18's don't look ridiculous on the stock 18's I just picked up, I think I'll go that route. I would have thought someone would have released an OEM sized set for winter by now!

You can get 275/40-18 winters if you are willing to go with RFT. Pirelli makes them and TireRack has them in stock. I'm not sure what issues the RFT might present aside from a likely harsher ride. My guess is that it would work okay, but I don't know. The other issue is those are some pretty expensive tires.