New wheels on the way, which size tires?

[Weasel]

Originally Posted by TaMbALoLoNg

I agree pretty much 100%, but the difference between 275/40 and 295/40 is only 8mm, which is practically nothing and you can pretty much balance it out if you have less PSI on your rear tires. It shouldn't put significant amt of stress on the drivetrain worth worrying about.

The difference between 275/40 and 295/40 equals out to 18 full rotations per mile!!! I have personally seen and had to fix the problems created by this, namely... transfer case. In 2000 - 2003 X5s it usually strips the splines at the front output shaft of the case costing you a front driveshaft and a transfer case. In 2004 - 2006 X5s it causes substantial wear to the clutches in the case where it transfers torque split to the front wheels, causing once again the transfer case to need replacement.

It would be like having different gear ratios front and rear of your 4 wheel drive... you just don't do that.

[X5-limo]

Originally Posted by weasel56

The wheel sare all tied together through the drivetrain, all pushed at equal speeds by the engine. The bigger diameter of a tire, the further it rolls per one rotation. If one set of tires are bigger than the other, the bigger set will push the smaller set and the smaller set will drag the bigger set... putting LOTS of stress on the drivetrain.

The tire sizes work probably different than you think. The 1st # is the tread width in millimeters, the 2nd # is the aspect ratio and works off of a percentage of the treadwidth... so a 275/40 is different height from a 295/40 and so on. The 275/40 and 315/35 are at the same rolling diameter which is why they are the best tire size option.

If you go on a site like tirerack.com and click "specs" when looking at a tire, it will give you the overall diameter and revs per mile for each tire size. Here's some to look at.

Dunlop did their homework to make tires the same size: http://www.tirerack.com/tires/Spec.j...e1=yes&place=0

Yet look at the different #s on the yokos:http://www.tirerack.com/tires/Spec.j...e1=yes&place=0

Thanx Weez,
I appreciate learning the universal theory (base foundation) of something and then go from there (as I'm seeing this thread doing). I assume that there's some equation that the tire techs use when they make their tire combo recommendations(?) - less they be sued left and right for things like 'stripped splines at the front output shaft of the case costing one their front driveshaft and transfer case' at the very least.

One point that's not debatable: You guys sure have some nice looking X5s!

[gatchalian]

is it a problem if you use 295 40 20 on all corners

[TaMbALoLoNg]

Will a 315/35/20 tire fit in a 20x9.5 wheel, what will be the con?

[TwinsPoppa]

Originally Posted by gatchalian

is it a problem if you use 295 40 20 on all corners

I remember a post that someone used 295s on all 4 corners with no problems using the stock staggered setup (9.5 and 10.5).

Originally Posted by TaMbALoLoNg

Will a 315/35/20 tire fit in a 20x9.5 wheel, what will be the con?

I've seen somebody shoe-horn 315s on 9.5s but I think you'll have problems with possible bead popping - not to mention probable improper tire wear. I have 295s on 9.5s and they're already not recommended.

[rayxi]

Originally Posted by X5-limo

I assume that there's some equation that the tire techs use when they make their tire combo recommendations(?)

It's not rocket science - just simple geometry. Check here. There are other sites with similar pages on the Web.

[TaMbALoLoNg]

Originally Posted by rayxi

It's not rocket science - just simple geometry. Check here. There are other sites with similar pages on the Web.

SWEET Link ray

[TaMbALoLoNg]

I've seen somebody shoe-horn 315s on 9.5s but I think you'll have problems with possible bead popping - not to mention probable improper tire wear. I have 295s on 9.5s and they're already not recommended.[/quote]

Have you had any drivetrain problems with your set up? (295/40)

[TaMbALoLoNg]

Originally Posted by weasel56

The difference between 275/40 and 295/40 equals out to 18 full rotations per mile!!! I have personally seen and had to fix the problems created by this, namely... transfer case. In 2000 - 2003 X5s it usually strips the splines at the front output shaft of the case costing you a front driveshaft and a transfer case. In 2004 - 2006 X5s it causes substantial wear to the clutches in the case where it transfers torque split to the front wheels, causing once again the transfer case to need replacement.

It would be like having different gear ratios front and rear of your 4 wheel drive... you just don't do that.

Makes perfect sense. The above is my current set up but I'm going to replace my rears to match my 275 fronts, I certaintly dont want future transfercase problems. So far I dont notice any problems right now and my X runs great. So i guess its either 275 or 295 all around. What do you think? This have been a very informative thread..great job guys

[TwinsPoppa]

Originally Posted by TaMbALoLoNg

Have you had any drivetrain problems with your set up? (295/40)

No and I hope it stays that way.

Originally Posted by TaMbALoLoNg

Makes perfect sense. The above is my current set up but I'm going to replace my rears to match my 275 fronts, I certaintly dont want future transfercase problems. So far I dont notice any problems right now and my X runs great. So i guess its either 275 or 295 all around. What do you think? This have been a very informative thread..great job guys

Assuming you want same size tires, because all your wheels are same sized, then IMHO:

wheel width = 9.5" or less then 275s
wheel width = 10" or more then 295s

If you have staggered wheels, IMHO, I think you should stick with different sized tires ... that's why the wheels are staggered! Hahahaha!