New wheels on the way, which size tires?
 

168's are coming 20x9.5 front and 20x10.5 rears.

275/40/20 front
315/35/20 rear

or
275/40/20 all the way around? I read a thread here of somebody who did that.

or
275/40/20 front
295/40/20 rear

Thinking about Vredestein Sessanta

If have my 131 on now that will be my dedicated winters.

I would go with the OEM sizes of 275/40/20 front, 315/35/20 rear.

The same size tires front and rear would have the rear tires not as wide as the rim, which would affect tire wear and would look funny too.

The tires front to rear really need to have the same rolling diameter to work properly in the 4 wheel drive system and not cause drive system wear, so the 275/40 to 295/40 idea is out.

And I have heard nothing but good about the Vredestines so far.

Good luck and enjoy the new wheels!

Go with the 1st option

I like the 20" wheel look. Not knowing much about tire-wheel basics, I would like to understand how when having the same rolling diameter is necessary to work properly in the 4 wheel drive system, that a '275/40 to 295/40' front-rear tire combo would be ruled out while the sizes of 275/40/20 front, 315/35/20 rear deemed acceptable?

Thanx

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

OH YEAH! i went with the Vredestein Ultrac Sessanta

OEM sizes of 275/40/20 front, 315/35/20 rear.....

Just recentley lowered with KW coilovers.....car handles great.....even in the ice and snow...carefully of course.


http://i42.photobucket.com/albums/e3...1/X5-Rich4.jpg
http://i42.photobucket.com/albums/e3...1/X5-Rich5.jpg

RR:thumbup:

[quote=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.
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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.

I don't know how you're doing your math but the difference in circumference is around 100 mm and the difference in diameter is 32 mm. That's a 4% difference in rolling diameter which is outside the recommended maximum difference of 3%.

There are other considerations besides drivetrain stress. DSC and ABS both rely on sensing rotational differences between tires. It's possible that introducing differences under normal driving conditions could throw those systems off.

Listen to weasel and go with the stock size tires.

I used the following sizes because my wheels are smaller width than stock:

265/45-20 (front)
295/40-20 (rear)

If you're going to use different width tires, in general, remember that your aspect ratios will be different to match the rolling diameters.

richirich,
Titz looking wheels and tires! :thumbup:
Especially like the look on your Ti Ag...
Wish I could justify a set for ours.
BR,mD

http://i42.photobucket.com/albums/e3...1/X5-Rich4.jpg

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.

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!

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

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

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).


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.

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

SWEET Link ray:thumbup:

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)

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:thumbup:

No and I hope it stays that way. :D

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! :D

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

No and I hope it stays that way. :D



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! :D[/quote] No shit Shirlock...

My wheels are not staggered they are 20X9.5. I think i'll stick with 295's all around. Lost sleep last night thinking abou this issue dont wanna risk ruining my transfercase. I was gonna do 275 all around but i was looking at my X long and hard, 295 make me feel more comfy overall.

Can 'size' make a difference, too....
 

The Weasel got me logically putting things into perspective: out of uniform spec wheel dimensions can potentially cause damage to the axle splines and transfer case.

In the same vein of gathering info to make a good choice of wheels, I need to ask what negative effects (stress, if any) is there on the drive components between using 17", 18", 19" and 20" wheels and tires? Or does one size put less stress on the components than the others? :dunno:

From what I gather, as long as you have tha same wheel rotations/mi on ALL corners so there is equal torque distribution, it dont matter what wheel size it is.

No and I hope it stays that way. :D


Twins...what is your wheel width all around? 9.5 or 10?

tire guys are not comfy putting 295/40 in front and they say its out of spec. maximum recommended width in front they say is 285/40. We're doing a test fit at noon today to see if 295/40 will work with no problems/scrapping. I will let you guys know.

295 is clear in front....:thumbup:

Did I say something to deserve this?! :confused:

I have 20 x 9.5s all around.

That's why I QUALIFIED my previous response and was steering you to 275s.

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

I have 295s on 9.5s but only on the REAR wheels.

What series is your rear and front? Or are they both 40's? what i'm saying is its not recommended to have different rolling diameters on your wheels (front and back). If you have 295/40 in the back then 275/40 in front is not good.

Oh man ... I KNOW that already ... you must not be following this thread ... I'll respond with a quote from my previous post #9 from this thread:

What I can sat about 17" - 20" rims is that the smaller rims will ride more comphy and feel smoother through the bumps by giving you a taller tire to absorb the bumps, but will be less stable than the bigger, wider wheels like the 20"s in the turns. The 20's will handle like a son-bitch in the turns by having a wider tire on the ground with lots less sidewall to flex/roll in the turns.

If you drive moderately and prefer comfort then the smaller wheels, if you enjoy "spirited" driving and would rather being able to throw it around like a sports sedan, then the 20's.

i have the 9.5 front and 10.5 rear and just switched to 295 40 20. currently have 4k miles with no problems...(hoping to stay that way) ride is much better.

MD - Thank you for the comp!

LOL! I had to justify mine to the MRS. LOL!

Rich:thumbup:

Thanx again for another down-to-Earth explanation that everyone can understand! :thumbup:

I will have 295's on 9.5 on all corners. This will sooth my driving style and look I want. I'm stoked,

Hahaha ... you know what they say (and it's usually what I do) ... it's easier to beg for forgiveness than to ask for permission! :D

Shhh ... don't tell my wife! ;)