[gtaccord]

Originally Posted by zipstic

You could be right about running narrower wheels making an impact and how much people are stretching their tires.

Logically I would think that going off of the revs per mile that TireRack posts would give you an accurate indication of how close you are front to back...unless the numbers are incorrect of course. Even with the differences in tire construction if it's softer/harder it would impact both the front and rear tires and be net neutral, right? I could definitely be wrong, but that's the way I'm thinking about it. (This assumes you're not doing anything crazy with PSIs and you're not fitting a 275 with tire on a 7" wheel paired with a 215 tire on a 10" wheel.)

You're correct that I do not put a lot of miles on my car, but it seems from reading posts on this forum that people have issues right away when they put on a staggered tire/wheel setup that the transfer case doesn't like rather than seeing issues after 10k, 20k 30k miles down the road.

To me, it seems like some transfer cases are very sensitive to staggered setups and some are not. This guy has been driving for over 60k with a 1.3% difference with no issues. His front tires are much smaller than his rear tires too. Although I do really like the theory about how the TC works and ideally running a larger tire up front.

You are probably right that some of the cars and transfer cases react differently. I personally have never had binding or loud noises or error lights but I do get drive line surge at highway speeds with my winter setup where the fronts are smaller. I would still recommend to stay away from that type of setup.

[mike5809]

On a side note tire rack is letting me replace my 225 with a set of 235 fronts.... so at least I didn't lose money on the tires. Hopefully no more issues as I will now have 235/35/19 and 265/30/19

Originally Posted by zipstic

I am running 225/35/19 and 265/30/19 on 313's (19x8 and 19x9) with Hankook Ventus V12 evo K110's. I've been running this setup for 3 summers, which probably equates to 7K total miles. I have not had any issues.

Those are the exact same tires and sizes I bad. I had to remove them within 100 miles due to the transfer case issues I was having. So strange.

Only difference are my wheels are 8.5 and 9.5

[zipstic]

Originally Posted by mike5809

On a side note tire rack is letting me replace my 225 with a set of 235 fronts.... so at least I didn't lose money on the tires. Hopefully no more issues as I will now have 235/35/19 and 265/30/19



Those are the exact same tires and sizes I bad. I had to remove them within 100 miles due to the transfer case issues I was having. So strange.

Only difference are my wheels are 8.5 and 9.5

Very strange. I wonder if LCI vs pre-LCI would have anything to do with it? I'm not sure if BMW used different transfer case model numbers...

[Priority 1]

Here is information that I received from Michelin. The first response was when i was making sure the tire sizes would work for my application, and the second response was earlier this year when i was trying to figure out what went wrong from someone more technical. They are somewhat contradictory in that the first one says the RPM specs are exact, and the second one says they aren't even measurements but rather they are what the European Tire and Rim requires them to be based on their dimensions. The second point in the second response agrees with my reasoning why these tires might actually be different because of the belt package, but then wouldn't that mean that the European Tire and Rim data is worthless?

In the end I think I need to pick one of three choices:

1. 225/40R19 with 255/35R19 PSS which is what they are using on brand new xdrives from the factory.

2. 235/35R19 with 265/30R19 PSS and have them run on a hunter machine with transaver to double check before i use them.

3. 235/35R19 with 265/30R19 Continental DW which many people have had on xdrive.

Response 1:
Yes, the posted data on rev per mile on our web-page would be exact. However, each tire manufacture will have different overall diameters for the same sizes. These tolerances have to be within certain governmental guidelines.. However, the variation between manufacture tires would be very similar. We would recommend that you check with your local BMW dealer for tolerance guidelines for the BMW X-Drive.

Consumer Care Department
Certified Michelin Product Expert

Response 2:
To address some of the questions below.

1. The RPM specs listed for our tires are not actual measurements. Rather they represent the center of the ETRTO (European Tire and Rim) design window. The actual RPM measurements may deviate slightly from the center of the window, but are within the ETRTO tolerances.

2. RPM is not substantially impacted by rim width, alignment settings, tire pressure, or even wear (believe it or not). It is a function of the belt package.

3. I would recommend staying with the factory OE tire sizes.

TCAR/MKT/PCM (Product Marketing)

[Andrewe92]

235/35/19 265/30/19 on my 2011 xdrive e92 n55.. it's been great so far for about 7k miles! only thing is sidewall is soft from what I heard so be careful not to hit any bumps too hard to cause a bubble.

[Mike.]

just picked these up today.. WOW so much better than the run flats. Like glue!! shaved off 16 lbs of unsprung weight too.