[08msportx3]

20x8.5 ET 33 FACTORY SIZE IS 245-35-20

20.9.0 ET 44 FACTORY SIZE IS 275-30-20

I would like to do 255-35-20 and 285-30-20 but its possible the wheels are not not wide enough for the application possibly . This size has much more tire sizes available

Or put 245-40-20 and 285/275-35-20

please help me for the best tire size other than OE sizes because that size is too thin for me and rides to rough for me.

[valbmw]

I like yours 373M whels very much, this is probably the best OEM wheel design of today. You noticed it right, the factory tire sizes fit the factory rims well. But if you want some wider tires you still can do it with OEM rims, but your wheels will look like meaty and the car may start handling softer.

Based on many observations the normal rims/tires square fitments (no stretch) are: 8,5"/245, 9"/255, 10"/285, 10,5"/295. As good example, please see below pics of my wheels 20x8.5 245/35 and 20x10 285/30. The tires sit flush, with square sidewall. With the wider rims I would get the tires stretched a bit. My offsets allow me not going to stretch, so here we are.

If you plan of moving to wider aftermarket wheels, I would recommend you to check the setups with perfect fit of rolling diameters (also recommended for xDrive):
20x8.5 245/35, 20x10 285/30
20x9 255/35, 20x10,5 295/30

As for the 245/40, 285/35 etc. I never heard anyone was using it on F10 because of much bigger size, also rolling diameters of the fronts vs. rears will be too different.

If the issue is the whole ride feeling is too rough for you, maybe choosing of 19" rims instead of 20" can solve it. Bigger rims leave less room for rubber, this is easy to understand. Needless to mention changing suspension settings if the car has the DDC.

Hope it helps.

[08msportx3]

Well this all makes sense for sure . I will say I had the 351m wheels and they still ride harsh but the tires are old and RFT. I'm going away from RFT and hope to accomplish that with a set of Michelin AS3 all season tires 285-30-20/ 255-35-20 but your saying might look to meaty but I think I might be ok with that . I just bought these wheels and don't plan to swap out with aftermarket wheels . I was going to do the 7series tire setup 245-40-20/ 275-35-20 but just not sure what to do. Tire rack only has a small selection of all season tired which are likely the Continental DWS which I had on my e90 and were great but after 2 years and they cupped and I wasn't happy with the handling . As its looking I will have to go back to them

[valbmw]

OK I see. My car came with 18" 350M with ContiSport3 RFT from factory as they were a part of M Sport package. We have summer and winter here, so I sold the RFT tires immediately, got these 20" wheels for summer and another set of serious winter tires 255/45-18 for the 350M. So if you will need to see how 255 look on 8.5" and 9" wide rims, I can take pics.

I would like to drag your attention to the following two things.
First, the 7-series wheels don't work well for the 5-series: they have different specs so handling will get worse and aesthetically they will look weird. Don't know about fitment issues with the diameter, but speedometer will show incorrectly, at least.
Second, running all-seasons will save you some money, but in this case you have permanent below-medium handling quality, because thread design and temperature properties of rubber must fit very tightly every season's conditions.

This is not just for fun the most of owners have high performance summer wheels and something easier for the colder season, except the lucky folks from the very south who need just one wheel set.

Maybe we should discuss in more details why you link tire size and ride being rough, this sounds something new to me. The whole forum is fighting against the F10's floaty and soft suspension and low steering feedback as a consequence of bloody green technologies (eco pro, electric steering etc.) The only reason of feeling the wheels as rough is RFT tires but this subject is simple: everybody are getting rid of them.

Having said that, I understand you have your own plan and style. However having a single set of cheaper all-seasons with wrong specs doesn't look a good way of improving ride quality and handling. I would recommend you to check one more option: good summer tires for your current 20" rims. Here the set of 245/35, 275 or 285/30 looks probably the best.

[lsturbointeg]

Good info here ya'll!

[.BMW.]

Since you would like more sidewall, your car has xDrive and the wheel widths are given, I would say that 245/40-20 front and 275/35-20 rear is your only option.

[08msportx3]

ITS LOOKING THAT WAY . Thanks Guys

[valbmw]

You're welcome! And I wouldn't ever recommend you whatever I don't want for myself.
Good look and take care!

[08msportx3]

Ok I decided to go with Michelin 255-35-20 and 285-30-20 and they look incredible. Will post pics tomorrow . I did put on 12mm spacers in rear