[m340i.kai]

I picked up my car 3 weeks ago and I realized most of the xdrive model with 18in factory wheels are squared (225). However mine is 225 front and 255 rear. Is that going to be an issue? I saw the ordering guide for 2020 and noticed it is not possible to run staggered for 18 in. I bought the car used so I don't know if it was a factory option or it was replaced. Please let me know if this was an option bc i know there are some specific rules you follow when running staggered on x drive.

[G22b58]

I have staggered 18" from factory on my 2021 M440i xDrive (in Europe).
I have realized that when times comes to replace tires, there are not much to choose from if I want to stay with BMW recommended (star marked), and I plan to do that. I asked Michelin about rolling circumference of their PS4 models in these sizes (which were star-marked but not suggested by Michelin web-tool for my car). The answer I got showed a difference of more than 1% even in the same "nominal" size.

[Bc2005]

If it was a factory option the larger tires usually also have a wider wheel (1”?).

You also can’t compare tire diameters without the full tire size description. For staggered factory setup they use a wider rear tire (the 255 vs 225), but the profile/sidewall height is different (e.g. 255/35 vs 225/40), so the total tire diameter is nearly the same.

[G22b58]

Originally Posted by Bc2005

If it was a factory option the larger tires usually also have a wider wheel (1”?).

You also can’t compare tire diameters without the full tire size description. For staggered factory setup they use a wider rear tire (the 255 vs 225), but the profile/sidewall height is different (e.g. 255/35 vs 225/40), so the total tire diameter is nearly the same.

18" staggered option 1R3 on M440i in Europe comes with:
F: 7.5 J x 18 ET25, 225/45 R18 95Y
B: 8.5 J x 18 ET40, 255/40 R18 99Y

Actual difference in rolling circumference is possible to measure (with ProTool for instance). Yes, a bit excessive but I did to make sure
A less precise method, but can still verify that back to front is about right, is to measure the difference in wheel rotation (foto of the air valve at start and end) over a driving distance of around 20m or so. Driving at speed is not exactly the same but 1% difference is easily detected.

[m340i.kai]

Originally Posted by G22b58

18" staggered option 1R3 on M440i in Europe comes with:
F: 7.5 J x 18 ET25, 225/45 R18 95Y
B: 8.5 J x 18 ET40, 255/40 R18 99Y

Actual difference in rolling circumference is possible to measure (with ProTool for instance). Yes, a bit excessive but I did to make sure
A less precise method, but can still verify that back to front is about right, is to measure the difference in wheel rotation (foto of the air valve at start and end) over a driving distance of around 20m or so. Driving at speed is not exactly the same but 1% difference is easily detected.

I believe we have the same wheel size because we run the same tire size
F: 225/45/18
R: 255/40/18
I am not too sure about the actual wheel width/ET. I don’t think this will be an issue and eventually I will replace them with apex wheels. And their website has guides for x drive models. I also think it’s dumb that m performance models have 18in wheels.

[G22b58]

Originally Posted by m340i.kai

.... I also think it’s dumb that m performance models have 18in wheels.

Just to give another view on the subject than that "18" looks too small".
(Yes for tracking I would anyway get another set, with better tires in 19".)
With larger wheels, the brakes look smaller.
The impression of the wheel to fender gap depends on what you look at. I suggest that my slightly lager tire side walls makes the wheel gap look relatively smaller than with 19 or 20" (and wheel gap is not too much on a M440i with adaptive dampers).

[m340i.kai]

Originally Posted by G22b58

Just to give another view on the subject than that "18" looks too small".
(Yes for tracking I would anyway get another set, with better tires in 19".)
With larger wheels, the brakes look smaller.
The impression of the wheel to fender gap depends on what you look at. I suggest that my slightly lager tire side walls makes the wheel gap look relatively smaller than with 19 or 20" (and wheel gap is not too much on a M440i with adaptive dampers).

Can you send pictures of your wheels/fender gaps? I’d love to see it with adaptive dampers. Mine doesn’t have it so it looks like a monster truck. I can feel every bump on the road. I don’t really mind it unless I’m in eco pro. Also I’m getting h&r lowering spring to resolve that issue with spacers.
F: 12mm
R: 15mm