Running different tread tires rear/front asking for trouble?

[omodos]

Hello all, just need to get the truth on this , does running different treads front/rear kill the drivetrain faster than if 4 tires on both axles are identical in tread pattern? Can't really get my head round it? Are the sensors on the x so adept at figuring out the traction on each tire and thus adjust output to each wheel accordingly, so having different treads throws this out and causes the x to compensate unnecessarily causing increased tramsmission wear?or am.talking gibberish?

[upallnight]

As long as the circumference of all tires are the same you shouldn't have any problem. If the circumference was different, one wheel would be rolling faster than the other. Think of a ice skater at the end of a long line of skaters, the one in the middle would hardly be turning, but the one at the outer edge will be moving really fast to keep up.

[Qsilver7]

Take note to understand the difference between a standard, a suggestion, a recommendation, a requirement or a warning in the info below from the BMW TIS.

Also understand that a tread pattern will react a specific way on the surface that it is running on. An AWD vehicle is reacting to the surface from both the front & rear axles...if the tread design is different between the front & rear axles, then the reaction may also be different which could affect how the vehicle handles or reacts.

[andrewwynn]

What he said about the handling characteristics. They need to be similar types of tyres


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[Bdc101]

If they are similar types it should be fine. Sticky on one end with a crappy all season on the other can be dangerous, and you may not know it until you have a situation where you need to avoid something.



Put the better tires on the rear if you have to drive that way. Also as others mentioned, if they have any significant difference in circumference you will be shopping for differentials soon.

[omodos]

Originally Posted by upallnight

As long as the circumference of all tires are the same you shouldn't have any problem. If the circumference was different, one wheel would be rolling faster than the other. Think of a ice skater at the end of a long line of skaters, the one in the middle would hardly be turning, but the one at the outer edge will be moving really fast to keep up.

okeee thanks, in the past my rears were wearing faster due to camber, now its the up fronts so in essence the circ. has changed in the past, just was reading on the woes of x3 owners who damaged the transmission due to mismatched tires treads

[andrewwynn]

According to the experts at TireRack, the tires on xdrive cars can be different sizes from original equipment (but must be within 3% of original tire diameter), and they need to be within 1% (not to exceed) diameter size of each other to not cause problems.

Some quick math:

31/2*0.01=0.155

Just about 5/32" difference in tread depth when starting with identical tires.

https://www.carbibles.com/calculators/

I use this site for comparison of sizes (to choose a spare tire size for example, or determine what size to use when picking a wider tire and keep speedometer "accurate". (In quotes because BMW adds 3mph to actual speed other than in Japan)

Looking at the two main sizes spec'd for E53: 255/55/18 and 235/65/17 and they are only 1.2mm difference in rolling circumference or 0.05% difference.

(Stunningly similar sizes).

I have pre xdrive which can handle more difference with open differential split using a 2/3 ratio planetary gear in the transfer case and my spare is about 1.5% difference in rolling circumference.

I would measure the actual tire circumference with a tape measure (wrap with the numbers toward the tires) not knowing how the mfg tolerance will affect things.

2225/25.4/100*8=7.008

7/8" difference in circumference. (a number large enough to get an accurate measurement.

To get an accurate rolling circumference, you could mark the tire with some chalk and drive, measure between the marks on the ground.

[omodos]

I hope I prove myself wrong, but gone and did this fronts had no meat on them near to balding (original tires all were identical size and tread except for fact that fronts treads all but gone)rears were fine, so I put a set same size 2365/65 r17 up front but different treads and brand.

Now get an odd shudder on slight inclines at 1400-1500 rpm....is this indeed compensation trying to made courtesy of the Xdrive system? and I am killing the transfer case with this?

Dang just didn't know it could be so sensitive , what is more confusing one fella that had same symptoms (but didn't do tire thing i did) changed transfer case oil and all good...so cant tell if it is coincidence or not and down to my tire change escapade

[omodos]

please see my post DONT DO WHAT I DID...
in my personal experience after doing this and putting on 2 other branded/tread type up front , I had the shudder issues on inclines and 1500rpm and even when slowing in traffic at slower revs

When i change all 4 to set of new identical tires (not i roll 235/65 r17 on all sdeis). I was ok again shudder gone.