[EBRSKIH]

Will be hopping into a 2012 550i Xdrive. I have 20 inch wheels and was wondering what tire setup I can run without messing up the xdrive system, I know there is a formula or way of figuring it out but I couldnt find anything thru the search. Front is 245/35/20 and the rear is 285/30/20. Thanks.

Emir

[bimmer man]

hey. I orded 20" 373M factory wheels for my 535d xdrive and tires dim. are 245/35/20 in front and 275/30/20 rear. And star marked wheels only, for not messing up Xdrive system.

[Hunter5179]

Originally Posted by bimmer man

hey. I orded 20" 373M factory wheels for my 535d xdrive and tires dim. are 245/35/20 in front and 275/30/20 rear. And star marked wheels only, for not messing up Xdrive system.

That's the same sizes I have but what are STAR marked wheels?

[mgcyr]

It was recommended that I go with 285/30/20 in the rear. What would the difference be?

[bimmer man]

hey. 285/30/20 are not rigth dim. rear Wheels going slower than front wheels and you will fuck upp our xdrive sytem

[bimmer man]

Originally Posted by Hunter5179

That's the same sizes I have but what are STAR marked wheels?

All bmw xdrive have star wheels from factory, star mark are a quality mark for absolutely round tires. best off the best. A STAR ARE MARKED ON TIRE.

[mgcyr]

Originally Posted by bimmer man

hey. 285/30/20 are not rigth dim. rear Wheels going slower than front wheels and you will fuck upp our xdrive sytem

Are you sure about that? The 285's are closer in diameter to the fronts than the 275's.

[bimmer man]

yes. I talk to BMW Norway and they say. If I have any diffrent tire set upp. I will loose my Worreny on Xdrive system and gearbox.

[Hunter5179]

245 front and 285 rear on 20" does have a closer rolling diameter than 275's but either setup is fine.. nothing major.

[Hunter5179]

245/35/20 fronts Speedometer Difference: 0.154% too slow with a diameter difference of .15%..............For 275/30/20 rear's Speedometer Difference: 0.834% too fast with a Diameter difference of .83%........For 285/30/20 rears the Speedometer Difference: 0.077% too slow with a Diameter Difference of .08%

The difference in rolling diameter for either of these compared to stock is really negligible and should not affect the x drive at all.. Its when rolling diameters exceed 2.0% and definitely above 5% is not good.

[EBRSKIH]

Originally Posted by Hunter5179

245/35/20 fronts Speedometer Difference: 0.154% too slow with a diameter difference of .15%..............For 275/30/20 rear's Speedometer Difference: 0.834% too fast with a Diameter difference of .83%........For 285/30/20 rears the Speedometer Difference: 0.077% too slow with a Diameter Difference of .08%

The difference in rolling diameter for either of these compared to stock is really negligible and should not affect the x drive at all.. Its when rolling diameters exceed 2.0% and definitely above 5% is not good.

So the dealer will agree that there will be no problem? I honestly have no clue how you got these numbers but it seems like you know what youre talking about. The way I thought about it was that the 245/285 setup will work because the X6 runs a 275/315 which is a 40 difference from the front and the rear as is the 245/285. But then again I thought that the profile of the tire would have to be adjusted in order to have a synchronized spin between the front and rear..

[Hunter5179]

I got that info off of a tire calculator. You punch in your stock setup then you punch in the tires you want to put on and it gives you the rolling diameter difference. Tire profiles usually do have to be adhusted fron and rear to achieve the best rolling diameter that's why the profile in front is 35 and the rear 30. I can't say if the dealer will agree but the rolling diameter difference is so small that if they did make a stink its only because they want to be dicks. It really wouldn't cause an issue with that setup either 245/35/20 front with a 275 or 285(slightly better)/30/20 rear.

[EBRSKIH]

Sweet thanks for the info mind sharing the website for the calculator? I just got the car today just waiting for some warmer weather so I can put on the wheels..not a fan of the 245s at all. You running your stock wheels now?

[bimmer man]

ok. so in us cars have 245 in front and rear? In Norway are 8"x18" 245/45/18" front, and rear 9"x18" 275/40/18" rear standard. and 8,5"x19" 245/40/19" front, and rear 9"x19" 275/35/19" and 8.5"x20 245/35/20 front 9"x20 275/30/20" as option. I vent for 20" for summer and 18" for Winter, I see, 245 in rear givs not a good look???

[Hunter5179]

Originally Posted by EBRSKIH

Sweet thanks for the info mind sharing the website for the calculator? I just got the car today just waiting for some warmer weather so I can put on the wheels..not a fan of the 245s at all. You running your stock wheels now?

Here is the link of where I did the calculations. http://www.1010tires.com/TireSizeCal...?action=submit Yes im running stock now just waiting for my Forged 1's to arrive.

[Hunter5179]

Originally Posted by bimmer man

ok. so in us cars have 245 in front and rear? In Norway are 8"x18" 245/45/18" front, and rear 9"x18" 275/40/18" rear standard. and 8,5"x19" 245/40/19" front, and rear 9"x19" 275/35/19" and 8.5"x20 245/35/20 front 9"x20 275/30/20" as option. I vent for 20" for summer and 18" for Winter, I see, 245 in rear givs not a good look???

245's squared is fine but for improved handling wider rear tire is better and looks wise much better. Also can put more power down because of the better grip.

[cdogasman]

Do you know if the offset on the staggered version in Norway is different as well? Offset on US version with M pkg is 35mm all around (on 19x8.5) yet 550i non xdrive with M pkg has 44mm offset in rear (on 19x9)

[bimmer man]

Originally Posted by cdogasman

Do you know if the offset on the staggered version in Norway is different as well? Offset on US version with M pkg is 35mm all around (on 19x8.5) yet 550i non xdrive with M pkg has 44mm offset in rear (on 19x9)

Hey cdogasman. On all Xdrive f10 we have 44mm offset in rear on 19" and 20". But f11 has 35 mm offset all around (stationwagon)

[remmib]

The front (and rear on the square setup) is ET33, not ET35 for OEM 19" and 20" F10/11 wheels.

[bimmer man]

Originally Posted by remmib

The front (and rear on the square setup) is ET33, not ET35 for OEM 19" and 20" F10/11 wheels.

0k. sorry.

[Judah]

Here's how you get tire diameters:


245/45/18

245 / 25.4 = 9.6457
9.6457 x 0.45 = 4.340
4.340 x 2 = 8.680
8.680 + 18 = 26.68

26.68 is the overall tire diameter


For MPH tire speed based on RPM:

26.69 / 26.00 = 1.0261
1500rpm / 1.0261 = 1461
1461 / 13.211 = 110mph




These are very basic easy to use laymen "equations". Your actual overall tire diameter will vary based on vehicle weight, tire psi and quite a few other variables. For a more accurate RPM to MPH numbers you will need engine speed, transmission gear ratio and differential gear ratio.


I hope this helps..

[EBRSKIH]

JUDAH. you is the man. thanks a lot.