Advice for a newbie

[alangs1200]

OK so we've just purchased a 2012 2.0i sDrive MSport for my good lady - pick it up when we're back from our hols in a couple of weeks. The one thing I will want to get for it are some rims and winter tyres. From the dealer the car is on M Sport 19" rims with 225/35 at the front and 255/30 at the rear. In terms of winters I'd prefer to put the car on 17" rims which I believe to be standard fit on the Z4 with a tyre size of 225/45 17. Now this is the first time we've ever had a car with different size tyres front and rear. So am I right in assuming (I know the rolling radius is right) that, with the winters, I can have the same size tyres front and rear when the M Sport wheels have different sizes front and rear? Having had a good trawl through it seems that this is OK, but confirmation would be great. Also, it appears that all these different BMW rims are identified by their numbers. What should I be looking for in terms of the identifying numbers for 17" BMW rims when I start to look for a second hand set of BMW 17" rims. Thanks in advance for any advice that long-term Z4 owners can share.

 

[metal licker]

Hi and welcome to the forum
There's a number of 17" alloys that will fit your Zed try - http://www.realoem.com/bmw/enUS/select
Put your details in this should tell you what was originally fitted by BMW

 

[alangs1200]

Thanks for that metal licker. Very helpful site. The 19" rims are the original factory fit although whether they were standard or a customer option at the time I have no idea but I assume standard as BMW designate the model as the M Sport. Either way this has certainly helped me understand the rim options and which BMW numbers fit the car in a 17" version.

If I understand correctly then the 276 and 290 rims are only available as an 8J x 17 (ET29) front and rear. These would obviously run 225/45 17 tyres.

But the 292 and the 514 rims come with the option of fitting an 8J x 17 (ET29) on both front and rear (running 225/45 tyres); or you can fit those rims on just the front and fit an 8.5J x 17 (ET40) version on the rears. Now I know you can put a 225 on an 8.5J rim but it's not ideal with a 235 or 245 preferred. A 235 would be OK from a rolling radius perspective, just a 1.4% variance from the 225 - so well within the tread depth variance.

So, is it better to go with 8J rims all round, with 225/45 tyres? Or better to go 8.5J at the rear and fit 225/45? Or 8.5J at the rear and fit 235/45? Any observations or suggestions as to the pros and cons of these choices would be appreciated.