[Stew_Pid]

I've trawled through various other posts including the long thread about OEM wheel sizes etc but I couldn't find the answer to my question.

I am looking at a set of wheels for my 2013 F31 xDrive. They're 437 reps I believe.

Front: 8.5 x 19 + 245/35/19
Rear: 9.5 x 19 + 265/35/19

Is this ok for an xDrive?

Thanks.

[alohasurftoad]

tire sizes are not OK for x-drive

[Stew_Pid]

Thanks alohasurftoad.

What are the implications of running incorrect tyre sizes such as this?

[alohasurftoad]

Originally Posted by Stew_Pid

Thanks alohasurftoad. What are the implications of running incorrect tyre sizes such as this?

you will damage and eventually destroy the x-drive transfer case. for x-drives the difference in front and rear tire diameter should be less than 1.2%, use 1% to be safe. ideally they should be close to equal as possible. 0% difference being the same diameter.

tire size combo such as 235/40/19-265/35/19 would be 0.4% and work fine for x-drive.

[Stew_Pid]

So when using this tool http://www.rimsntires.com/specspro.jsp I need to aim to have the tire diameter <1.2% taller or shorter?

[alohasurftoad]

Originally Posted by Stew_Pid

So when using this tool http://www.rimsntires.com/specspro.jsp I need to aim to have the tire diameter <1.2% taller or shorter?

www.tiresize.com is easier. use tire size comparison

the difference between the front and rear tire diameters needs to be less than 1.2%. combinations where the value approaches 0% is better. lower smaller number is better, 0 is best.

[Stew_Pid]

Great! Thanks man, you've been a great help and potentially saved me from a disastrous purchase!

[alohasurftoad]

Originally Posted by Stew_Pid

Great! Thanks man, you've been a great help and potentially saved me from a disastrous purchase!

if you purchased it, assuming wheel offsets appropriate, you'd have to change the front tire size to 235/40/19 and you'd be all good for x-drive.

[Stew_Pid]

Originally Posted by alohasurftoad

if you purchased it, assuming wheel offsets appropriate, you'd have to change the front tire size to 235/40/19 and you'd be all good for x-drive.

Great, thanks again. The wheels are no longer a good deal for me as I would have to replace two almost new tyres.

[atblis]

Does rim width affect diameter? If so, how much? Is it even calculable?

[cfm56d7b]

If your vehicle is still under warranty, I suggest to keep wheels / tires the same for the duration of warranty EVEN if BMW offers other OEM wheel sizes compatible with xDrive drivetrain.

I know of one case where BMW declined to honor xDrive drivetrain warranty for F31 (station wagon in the US, touring in Europe) with BMW OEM 19" wheels which were an option on F30 sedan models, for example 401 19" Style wheels. The reason for warranty denial: 401 Style wheels were not a valid option when the car has been ordered.

[Stew_Pid]

Originally Posted by atblis

Does rim width affect diameter? If so, how much? Is it even calculable?

Absolutely, the wider the rim the flatter the profile and therefore a reduction in diameter. Experiment with the tools linked to above.

[atblis]

Which of those tools takes into account rim width and its effect on diameter?