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[AWD Addict]

Okay, I'm modifying my stock 18" wheel/tire setup to be my winter setup.

My stock 189s are staggered, 8.0" front, 8.5" rear.

I'm replacing the stock tires

F 225/40/18R
R 255/35/18R

with

F 225/40/18R
R 245/40/18R


My concern is that my tire manufacturer didn't have the exact measurements for sidewall / width as the stockers and how will that affect the XDrive system.

By my math, the stock setup has basically the exact same sidewall height front to rear (3.546" front versus 3.517" rear), and the new setup will be almost a third of an inch larger (3.546" front versus 3.862" rear) in the rear. Is that a big enough variance to be an issue with xdrive (or anything else?).

Am I getting way to insane in analyzing this? I've already ordered the rubber, so I'm hoping I don't have to change anything.

Thanks in advance all!

[sparkyg]

Errr, I wouldn't. Thats way too much diff. Your original wheels are 0.2% and now these are over 2%, that is a full order of magnitude.

Your money but I would not advise.

Some of the +1'ers are going to a 0.857% diff and that appears to be okay.

Maybe ask Gary@Tirerack

[AWD Addict]

Thanks for the advise, anyone else?

[Nikolas]

What you need to find out is the overall diameter of each tire. If you go to TireRack you can get the specs for the tires they carry. They list everything including sidewall, diamter, revs per mile etc. You want the front and rear diameter to be as close as possible - less than 1% difference. Since you are proposing the same profile of 40 and different widths, I am pretty sure that combination would be very bad for XI. I would stick with a 255/40 in the back and not worry about it. The reality is the wider the track, the better traction you will have in most packed snow and ice conditions. The only time that narrower theory of snow tires applies is on fresh untracked snow where there is less plowing resistance with a narrower tire.

[remmib]

Originally Posted by AWD Addict

Okay, I'm modifying my stock 18" wheel/tire setup to be my winter setup.

My stock 189s are staggered, 8.5" front, 9.5" rear.

I'm replacing the stock tires

F 225/40/18R
R 255/35/18R

with

F 225/40/18R
R 245/40/18R


My concern is that my tire manufacturer didn't have the exact measurements for sidewall / width as the stockers and how will that affect the XDrive system.

By my math, the stock setup has basically the exact same sidewall height front to rear (3.546" front versus 3.517" rear), and the new setup will be almost a third of an inch larger (3.546" front versus 3.862" rear) in the rear. Is that a big enough variance to be an issue with xdrive (or anything else?).

Am I getting way to insane in analyzing this? I've already ordered the rubber, so I'm hoping I don't have to change anything.

Thanks in advance all!

Wrong, the 189 are 8" front and 8.5" rear. Just go 225/40/18 all around

[AWD Addict]

Originally Posted by Nikolas

What you need to find out is the overall diameter of each tire. If you go to TireRack you can get the specs for the tires they carry. They list everything including sidewall, diamter, revs per mile etc. You want the front and rear diameter to be as close as possible - less than 1% difference. Since you are proposing the same profile of 40 and different widths, I am pretty sure that combination would be very bad for XI. I would stick with a 255/40 in the back and not worry about it. The reality is the wider the track, the better traction you will have in most packed snow and ice conditions. The only time that narrower theory of snow tires applies is on fresh untracked snow where there is less plowing resistance with a narrower tire.

Well, Nokain doesn't make a 255 40, and the 245 40's are 1.32% variance on the entire assembly diameter. I'm going to re-order 225s for all corners.

Thanks for the help guys.

[AWD Addict]

Originally Posted by remmib

Wrong, the 189 are 8" front and 8.5" rear. Just go 225/40/18 all around

Oops. Corrected.

[dakine]

I'm also ordering an xi w/ 18" wheels and have the same concerns you did. How did the tires fit and handle, and did you have any problems with the TPMS with the rear tires being smaller? Also, can you post up some pics? Thanks.

[AWD Addict]

Tires are great. I'm running 225s on all four corners. No problem with TPMS.

Here are some pics.

[Winston Wolf]

Just stick with the same size tires it came with....

http://www.e90post.com/forums/showthread.php?t=130231

[AWD Addict]

Originally Posted by Winston Wolf

Just stick with the same size tires it came with....

http://www.e90post.com/forums/showthread.php?t=130231

Nokian doesn't make the same sizes, hence the 225 all around.

[dakine]

Cool.. Thanks for the pics!! I was unsure about getting the 18" wheels with the sport pkg, but now I'm convinced I'm doing the right thing. How do the Nokians handle in snow, slush and ice?

[dakine]

Cool.. Thanks for the pics!! I was unsure about getting the 18" wheels with the sport pkg, but now I'm convinced I'm doing the right thing. How do the Nokians handle in snow, slush and ice?

[NJ335xi]

On my 335xi with staggered setup I went with 225/45/18 on the front and 255/40/18 on the rear for extra side wall. It made my speedo more accurate too! The diameter difference (front to back) is the same as stock.

See my post below.

http://www.e90post.com/forums/showthread.php?t=132580

[AWD Addict]

Originally Posted by dakine

Cool.. Thanks for the pics!! I was unsure about getting the 18" wheels with the sport pkg, but now I'm convinced I'm doing the right thing. How do the Nokians handle in snow, slush and ice?

We only had minimal snow since they were put on. Nothing deep. lots of wet and some ice, and they handled very nicely.