[Wlodi]

Originally Posted by snowbimmer

The 20" M850 wheels are: Front Dia - 26.75", Rear Dia - 26.50"

The 20" M5/8 wheels are: Front Dia - 27.58", Rear Dia - 27.86"

The 19" M5/8 wheels are: Front Dia - 27.34", Rear Dia - 27.98"
(These are the snow set - 705M)

This is only partially correct.
For the 850i and any nonM 8 series (F1X 6 series also) - if you use the OEM wheels the diameter is the same in front and rear. Only for OEM wheels marked with a star. The circumference is identical.

I imagine all star marked wheels create a set for a given BMW Model.

[snowbimmer]

Agreed. I was only using info from tire calculators since BMW Star info is impossible to find. It would be interesting to see how much variance they are from the calculators and if, in fact, they can make the front and rear tire diameters the same with all the their different staggered tire sets for their various models.

[Dasky_spas]

I put on the 813m front wheels on all 4 corners of the m850i with 275/30. However, I ended up having to use 3mm spacers in front to avoid being too close to the steering knuckle. It's an aggressive fit but it works.

[JtheW]

Originally Posted by Dasky_spas

I put on the 813m front wheels on all 4 corners of the m850i with 275/30. However, I ended up having to use 3mm spacers in front to avoid being too close to the steering knuckle. It's an aggressive fit but it works.

Please post some good pics. I’m really interested in doing this with the 4 fronts but running 255/295 tires.

[Dasky_spas]

295 nor 255 are ideal for a 9.5" wheel..

[Wlodi]

Originally Posted by snowbimmer

Agreed. I was only using info from tire calculators since BMW Star info is impossible to find. It would be interesting to see how much variance they are from the calculators and if, in fact, they can make the front and rear tire diameters the same with all the their different staggered tire sets for their various models.

I imagine the solution here is to get the list of OEM BMW tyre sizes with fronts 255-265/35/20 and rears 275-295/30/20.

If the case is different and for instance all OEM wheels have the same diameter then going for the OEM front from one model and the rear from other model. Within the same tyre brand and model of course. Just wonder whether the diameters are the same for non-Xdrive models.

If that would be the case then (maaaybe) the F80 tyres would be a way to go for the M8 wheels.

265/30ZR20 94Y front axle
285/30ZR20 99Y rear axle

Does anyone have an M3/M4 ?

[Dasky_spas]

Originally Posted by Wlodi

I imagine the solution here is to get the list of OEM BMW tyre sizes with fronts 255-265/35/20 and rears 275-295/30/20.

If the case is different and for instance all OEM wheels have the same diameter then going for the OEM front from one model and the rear from other model. Within the same tyre brand and model of course. Just wonder whether the diameters are the same for non-Xdrive models.

If that would be the case then (maaaybe) the F80 tyres would be a way to go for the M8 wheels.

265/30ZR20 94Y front axle
285/30ZR20 99Y rear axle

Does anyone have an M3/M4 ?

This setup wouldn't work either given the circumrefernce between the front and rear
is too great. The only option is to run 265 or 275/35/20 on all four. The weight of the car demands wide tires though so 275 are the way to go.

[Wlodi]

I imagine that since the OEM tyres are making a set for each model then the case might be the circumference might be exactly the same for front and rear regardless of the tyre sizes. At least this was the case for one of the oem sets I have checked.

[Sinister840]

I want to do something similar to my 840. Would like to hear back as you drive it more often what it feels like and if there is any rub at all... when you find a good dip to test the suspension.