MBE550

Can someone tell me what is the size of 550 sport stock wheel size?

I found some post saying front is 8.5 X 18, but could not find anything for the rear.

I have 245/40/18 and 265/35/18 now.
Has anyone replaced the rear to 275/35/18?
I saw a post mentioning 275 is better match in terms of size.

MBE550

I found the wheel size:

Front 18 X 8 245/40/18
Rear 18 X 9 265/40/18

265 is off by 1.6% in diameter and 275 off by 0.5% which is closer fit.
It does look like it's safe to fit 275 on 9 inch wheel.
In fact, many BMW comes with same wheel size and 245 front and 275 rear.

I'm just curious if anyone actually tried 275 in the rear with stock wheels.

amdeutsch

There are several that have done it.

P.S.

The wheel info is listed in your owner's manual

xr650rguy

Did it, love it.

245/40-18 front on stock 18 x 8.5" sport wheels
275/35-18 rear on stock 18 x 9" sport wheels

The car feels different (better) after the change. The only reason I can surmise why MBZ didn't equip the cars like this to begin with is that Conti and Pirelli don't make the 275/35-18 size.

amdeutsch

But Michelin does and that is also an OEM tire. There is another reason for this.

MBE550

After you changed the rear, does sidewall bulge more than the front?
I'd like to get 275 in the rear as long as there is no downside or negative effect.

amdeutsch

Yes, its simple math. The tire is 30mm wider whereas the rim is 12.7 mm wider when compared to the front.

Preferred fitment would be 9.5" but most tire manufacturer's allow for 9" fitment. Upside/downside is too complex based on your fielded questions. You either take the forum's word or do 265s.

NCE500

I've had CLS wheels on my car for over a year. The rear tires are 275/35/18 on a CLS spec 9.5 inch wide wheel. You can run 275's without issue on your wheels and car.