[tjbuggy2b]

I know I'm pushing the generally accepted limits of diameter difference (at 1.1%), with this combo but I really want to reduce the section width difference from the normal 40mm delta.

Anyone have experience with 255/35r20 & 285/30r20 on xDrive, or know of anyone that does?

[jag81]

Im running 255/35 and 295/30 on mine, no issues thus far... circa 5000 miles.

[tjbuggy2b]

Yeah, 255/35 and 295/30 is only a .2% difference in overall diameter. From my research, most people say to keep it under 1% for xDrive cars. What I'm wondering is if the 1.1% difference of 255/35r20 & 285/30r20 will piss off the AWD system.

[tjbuggy2b]

So, this is what I'm thinking, wheels and tires. Someone please let me know if this will rub anywhere with 1"-1.5" drop, or if the AWD system will have a problem with a 1.1% diameter difference!

Front: 255/35r20 on 20x9 et30
Rear: 285/30r20 on 20x10 et40

Alternate thought...

Square: 265/35r20 on 20x9.5 et30

[ezaircon4jc]

Originally Posted by tjbuggy2b

So, this is what I'm thinking, wheels and tires. Someone please let me know if this will rub anywhere with 1"-1.5" drop, or if the AWD system will have a problem with a 1.1% diameter difference!

Front: 255/35r20 on 20x9 et30
Rear: 285/30r20 on 20x10 et40

Alternate thought...

Square: 265/35r20 on 20x9.5 et30

I'm petty sure the difference has to be less than 1%.

[pperc]

Originally Posted by ezaircon4jc

I'm petty sure the difference has to be less than 1%.

Stock staggered set up is just over 1%

[ezaircon4jc]

Originally Posted by pperc

Stock staggered set up is just over 1%

Are you sure? I believe the difference is .1%...

245/40/19 and 275/35/19 is the stock staggered size.

https://tiresize.com/calculator/

[pperc]

Originally Posted by ezaircon4jc

Are you sure? I believe the difference is .1%...

245/40/19 and 275/35/19 is the stock staggered size.

https://tiresize.com/calculator/

For the 19s it’s -0.4% per that calculator. Where do you see 0.1%?
Then do it for the OEM 20s… it’s -1.1%.

[ezaircon4jc]

Originally Posted by pperc

For the 19s it’s -0.4% per that calculator. Where do you see 0.1%?
Then do it for the OEM 20s… it’s -1.1%.

Size 1Size 2
Diameter
26.7"
26.6"
-0.4%

Width
9.6"
10.8"
+12.5%

Sidewall
3.9"
3.8"
-2.6%

Circum.
83.9"
83.5"
-0.4%

Revs/Mile
755
759
+4

[pperc]

Originally Posted by ezaircon4jc

Size 1Size 2
Diameter
26.7"
26.6"
-0.4%

Width
9.6"
10.8"
+12.5%

Sidewall
3.9"
3.8"
-2.6%

Circum.
83.9"
83.5"
-0.4%

Revs/Mile
755
759
+4

Right. -0.4% difference for 19s OEM. The 20s come out to -1.1% diameter difference.

[tjbuggy2b]

Stock staggered setup is 245/40r19 (or r20) and275/35r19 (or r20), which is .5%

[pperc]

Originally Posted by tjbuggy2b

Stock staggered setup is 245/40r19 (or r20) and275/35r19 (or r20), which is .5%

This is correct for 19s. Are you sure 20s use 40 and 35 size tires? I have 19s so I can’t be sure on 20s, but last I was told they are 35 and 30. Hopefully someone else will clear this up with a photo.

Edit: https://tiresize.com/tires/BMW/M550i/. According this I am correct.

[tjbuggy2b]

OH! Interesting! My mistake. I'll have to do some more research to confirm but that would be awesome!

[lanlilan]

Mine came from factory with 245 35 R20 front and 275 30 R20 rears on Xdrive.

[tjbuggy2b]

Nice!

[6SPD_S58]

I'm running 255/35 and 285/30 for over 8k miles now with no issue

[Dasky_spas]

Originally Posted by tjbuggy2b

I know I'm pushing the generally accepted limits of diameter difference (at 1.1%), with this combo but I really want to reduce the section width difference from the normal 40mm delta.

Anyone have experience with 255/35r20 & 285/30r20 on xDrive, or know of anyone that does?

275/35/20 square, no problems

[tjbuggy2b]

Originally Posted by Dasky_spas

275/35/20 square, no problems

What offset, and do you have any pics?

[Dasky_spas]

I used 4 m8 813m front wheels, 9.5 28et. 3mm spacer in front only. It's on a m850i but this should be similar fitment.