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I just hit some road debris with my 2011 JKU and got a non-repairable gash in one of my tire sidewalls. These tires are about a year old and have 8-10/32 tread left. Never heard this before, but both my mechanic and the guy at the store say that I can’t just replace the bad tire with a new one. They say that unless all tires have equal wear — within a few 32ths — that the diff or transfer case can be damaged.

I find this hard to believe, since both devices are designed for r/l and f/r differences in rotation much greater than a little tread wear would cause.

Has anyone else heard or experienced this? I’d love to know the reasoning.


Ken
 

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This is true, if you're driving around in 4x4 on pavement, which is dumb. Since you're only supposed to use a part-time transfer case on slippery surfaces, no it's not an issue as long as the tires are close the same size.

I mean, a lot of people do 5 tire rotations, so one tire is always going to be like 5k off of the others in terms of wear. Likewise, you might not have the same tire pressure in all tires all of the time. On top of that, going around a slight corner in 4x4 causes different tire rotation speeds on all four corners.
 

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The diff is designed exactly for the purpose of allowing one wheel to turn faster than the other. So no problem there.

The transfer case wouldn't even come into play unless you were in 4WD on a paved road; since you're not, there will be no binding in the transfer case from having a driveshaft turn a little faster than the other.

Just put the new tire in the rear, and your next best tire on the other rear wheel.
 

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When I replace one tire, I always replace two - I prefer to keep the newest and like tread on the rear (drive axle in 2wd).
 

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It is possible to roast a differential with wildly different tire sizes. I was a passenger when we got a flat in front of a FWD vehicle. The owner put the donut on the front and headed down the highway. A few minutes later, we smelled something hot -- in a bad way. Pulled over, differential was toasty hot and all the old oil and road grime caked on it was smoking pretty good.



Now, the difference in tire size due only to wear may not be enough to cause problems, I don't know. But the idea that a diff can be damaged by working it hard is not without merit... and when I personally have to use a donut, I ain't putting it on a driven wheel.


(AWD is another story. For example, VW vans use a fluid coupling between the front and rear, and VW has warnings in the owners manual that uneven tire wear can definitely damage the fluid coupling. Any difference in rotational speed is basically converted into heat in the fluid. That's okay for the occasional wheel slip AWD is designed to handle, but constant use is another matter.)
 

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It is funny to me that people who do work like that don't understand how things work.
As mentioned, wildly different diameters can cause issues. But minor differences in diameter will make no difference.
I had a flat with the 37's on ours. I first replaced the flat tire with the spare (which did always get rotated in as I do 5 tire rotations), then after I had the flat tire replaced with a new tire I rotated the new tire in at the next scheduled rotation (I rotate when I change the oil). So, three tires with around 25,000 miles on them and one brand new tire. No problem. If you can't run tires of the same size but different amounts of wear, people who don't rotate in the spare (and there are more than a few) would be screwed when they get a flat as they would not be able to use the spare.
The front and rear differentials allow the tires to spin at different speeds as required. This happens a lot while driving down the road, even if the tires are exactly the same outside diameter. That is because every time you turn the tires on the outside of the turn have to travel farther just to keep up with the tires on the inside of the turn.
You may want a better tire shop.
 

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A new tire v. and old tire of the same brand/size shouldn't have any negative effect on the differential, but the Jeep's computer may have issues with it thinking one tire is 'slipping' and engage the BLD and/or throwing a trouble code.
 

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There might be some issues using new and worn tires on axles with traditional limted slip diffs considering that LSD's try keep both the wheels turning at the same speed.

But.. I'd be curious to know.. Has anyone on the forum ever had a problem using a newer tire and an older tire with more wear on the same axle???
 

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It is funny to me that people who do work like that don't understand how things work.
As mentioned, wildly different diameters can cause issues. But minor differences in diameter will make no difference.
I had a flat with the 37's on ours. I first replaced the flat tire with the spare (which did always get rotated in as I do 5 tire rotations), then after I had the flat tire replaced with a new tire I rotated the new tire in at the next scheduled rotation (I rotate when I change the oil). So, three tires with around 25,000 miles on them and one brand new tire. No problem. If you can't run tires of the same size but different amounts of wear, people who don't rotate in the spare (and there are more than a few) would be screwed when they get a flat as they would not be able to use the spare.
The front and rear differentials allow the tires to spin at different speeds as required. This happens a lot while driving down the road, even if the tires are exactly the same outside diameter. That is because every time you turn the tires on the outside of the turn have to travel farther just to keep up with the tires on the inside of the turn.
You may want a better tire shop.
You mean everything you read on the internet is not true? :jawdrop:

:)
 
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