hceptj

If anyone ever finds or gets an official answer from MB in writing I'd like to know what they say.

Odd Piggy

I think we might be running this issue into the ground. Over the 187,000 miles I owned it I ran 275-55R17 tires of all wear states on my ML350. The front tires wore so fast that if they weren’t rotated to the back every 3000-5000 miles, they would be down to the steel belts in 12,000 miles. There was never a problem with the transfer case or the differentials. It was still in marketable condition when I traded it in.

IMHO Mercedes 4Matic can well withstand the very minor size difference experienced with tires of different wear states. That is NOT the case on vehicles with 4WD and locking differentials or hubs. We have 4WD trucks for off road use. When the drive train is in locked 4WD configuration, tire diameters of ¼ inch or more on hard surfaces will put extreme stresses on all of the drive train components. Before these trucks get back on the road, the differentials/hubs need to be unlocked and the drive train put back into 2WD.

Odd Piggy

I don’t think so. Consider:
That 0.81 inch diameter difference is greater than any wear on a road tire for a GLK could ever be. ¼ inch (8/32 inch) of wear (1/2 inch diameter) takes a tire with 10/32 new tread depth from new to completely worn out.
And the tire with ¼ inch wear can’t be run on the same axle opposite a new tire very long because it is worn out, will not pass safety inspection, and needs replacement.

John CC

I think they are using the word "size" to mean the same thing as you would if you said "what size shoe do you wear" or, "what size tire do you have on that axle."
We covered that back in post #3. The difference between a new tire and a worn tire is going to be somewhere between one and two revolutions out of 100. If your differentials can't handle that you'd be restricted to driving in a straight line all the time.
Agreed!

MBKLUE

It seems there are five generations of Mercedes 4MATIC and three CURRENT versions. A lot of variation possible although the GLKs all had the same, just a change in automatic transmission when the updated GLK came out.

MBKLUE

I think it's very possible your ML may have had a more robust, heavier duty 4MATIC system than the "less premium" GLK/C-Class models. So not so sure how valid a comparison this would be for these purposes.

Odd Piggy

Good point. The W163 was a design from the 90s. I assumed that the GLK being much more modern would be more capable. But maybe not. The first gen MLs were truly off road capable and had selectable low range like the G-wagons. The GLKs had more limited abilities, maybe a simpler system. But I still think that if it can’t handle 1/4 inch wear difference, that’s a defect on a passenger vehicle.

Fagunza

I can't find the reference now but I recall a 4/32 tolerance. In support of this I reviewed the CPO paperwork on my wife's 2014 GLK. The measured tire tread depths when I bought the car were LF 5/32, RF 9/32, RR 7/32, and LR 7/32. So a Mercedes technician and his service manager signed off on this difference. Strangely, after the 250 mile drive home I measured the tires myself and found the LF to be a 4/32. So, I went to Discount Tire and had them replace three of the tires. And no, it wasn't worth the hassle to argue with the dealer because of the distance.

Regarding repairs, I go with the tire manufacturer's recommendations. Tire Rack is always a good source (see attachment).
Tire Rack tech advice

Megalomaniac1

A staggered Mercedes 4-matic set-up from the factory is out more than 3/32"
3/32" = 0.094" out
One example of many 2016 S-class front 245/40r20 rear 275/35r20 = diameter front 27.72- diameter rear 27.58 = 0.14 of a inch out