Different Tire Sizes lead to a ruined transfer case / differential - TWICE

[TyreLyre]

Looking to save a buck I had a set of used tires put on my E53. They installed the following:

Front: 235/65R17
Back: 255/65(or60?)R17 -- not sure of the aspect ratio because the car is STILL at the shop.

I drove without any issue ( apart from an occasional whirring sound near the end ) for about 6 months.

Then the transfer case went out so I took the car to the shop to have it replaced. 2 weeks later the new differential went out and it was back to the shop. Now they want to charge me again plus the pinion gear against the ring gear were both damaged.

Obviously I should have not let the tire shop install different sized tires but I've seen that some X5s have different sized tires so I wanted to get the expert's (you all) feedback on the situation and how responsible I should be for the second set of repairs.

Thank you in advance for looking in to this!


Vehicle info: 2004 E53 X5

[Qsilver7]

You can see from the owners manual...as well as the tire inflation chart on your driver's door/door jamb what the BMW recommendation is for tire sizes. Yes, you can use a staggered set-up but the BMW staggered wheels are also wider in the rear which accommodates the wider tire width and lower aspect ratio. The overall diameter/circumference should be within 3% of each other (basically the same rolling circumference).

You left off the suffix of your X5 so don't know if you have the 3.0 or not...but the tire recommendations are the same as below for 17" tires. You can google "tire size calculator" to find out if the tire sizes you have mounted are within 3% rolling circumference of each other:

[jclausen]

I don't think the shop knows what there doing we rarely have to replace transfer cases. Are the parts used? And what is the thing about replacing the ring and pinion. There going down the rabbit hole.

[bagekko]

I dont see how the non standard size tires would screw up the transfer case, would be a first if true. I ran a non traditional size on my E70 for 2 winters with no problems, 245/50-18 instead of the stock 255/55-18.

[peter2772000]

The idea is to keep the same rolling diameter difference between from and rear. Other than a speedo inaccuracy, it changes nothing. But if the OEM front tires are 15% smaller in rolling diameter than the rears, you need to respect that.

[burninator]

Running two different tire heights front to rear will definitely cause issues.

[ChrisMelnyk]

I'm not sure if this is a myth, but I've heard that running worn tires on one axle and new on the other can cause issues like this. Apparently it is that sensitive. That is why Discount tire (I believe) offers a tire shaving service, so you can actually match the wear of your old tires.... I'm just going to replace all 4 when I need to.

[coffs]

I'm not sure if this is a myth, but I've heard that running worn tires on one axle and new on the other can cause issues like this. Apparently it is that sensitive. That is why Discount tire (I believe) offers a tire shaving service, so you can actually match the wear of your old tires.... I'm just going to replace all 4 when I need to.

Only really old 4WD systems can cope with different rolling circumference front to rear or side to side. (Land Rover, Jeep)

Just about everything post 2000 will cause severe damage if there is a difference, that's why tire rotation is crucial to extending the life of the tires and time between changes. You must always change all 4 tires at the same time when buying new.