[htang555]

Hey guys,

I'm new here and purchased a used 335i GT Msport that I am very happy about!

Unfortunately I am pretty novice when it comes to tires/wheel sizes.

I went to get it inspected at my local BMW dealership and everything is in good condition. The only concern was the tire sizes. They don't have stock wheels on them, and have weird tire sizes. Stocks are:

F: 225 45 R19
R: 255 40 R19

My sizes are:

F: 235 35 R19
R: 265 30 R19

I have a few questions about this setup:

1) Does the rim width affect the overall diameter of the tire?

2) Will I be fine running these or will it ruin my diff/transfer case?

3) If the aftermarket wheels are indeed a different size (19x8.5 and 19x9.5 vs stock) will I be fine running them?

4) How much of a difference in wheel size overall diameter can the xdrive system take before faulting? I am used to Audi's Quattro where the diameter had to be exactly the same (not sure about the xdrive setup).

5) If I can't run this setup how urgently should I change them?

I've driven them for about 400Kms like this already, and don't know how long the PO has had them on the vehicle for. Would appreciate any input! Looking forward to learning!

Thanks in advance.

[htang555]

So I punched the specs in a calculator (I think its the right one) and got the following (In screenshot, left are fronts). The total variance in the Stock Diameter is 0.99 and in my set is 1.01. Should that be fine (other then the speedometer adjustment)?

[Billfitz]

The main problem you'll have with those is how easily the tires and rims will be damaged by potholes. If they're summer only you may be OK. But I would never run less than a 45 aspect ratio in winter, unless said winter is in Florida.

[htang555]

Thanks for the suggestion. I live in Canada so we can get some harsh winters here . Do you recommend dropping down to maybe a winter set of 18's? Something like a 245/50/R18 or a 225/55/R18?

[Billfitz]

For winters go to 18s, 17s if they'll fit. I have 225/55-17, not only for less potential for pothole damage but because they ride better. Air and rubber absorb shock and vibration, aluminum doesn't. Super low profile tires on big rims look good, but so do six inch stiletto heels on a woman. They're equally practical, which is to say not at all.

[htang555]

Thanks for the tips. I ended up going with 18's on 245 45 18 tires ( a square setup with runflats) if I did the calculation right they should be fine.