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replacing one rear tire?

its_me_walt

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Hey folks, I hit a piece of metal on the highway and murdered my passenger rear tire.

I have a PP 17 with torsen rear , 9k miles on car/tires. Im getting exact replacement tire. Should i be concerned about treadwear difference between driver and passenger rear tires? with this hurt the LSD? nothing is mentioned in the owners manual
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sk47

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Hello; Here is the way I have understood it for a long time. Back in the late 1950's one of my uncles drove up from Florida to KY. Along the way he had a flat or blow out. While in Middlesboro, KY visiting he was driving around on a replacement which was a different size on the rear axle. The tire wheel one one side different than the tire wheel on the other side.
I was a child then but recall the story. Seems he drove too long on mismatched sizes. Damage was done to the rear end. It likely was an open rear end. I can recall seeing his car and there was a visual difference so the size difference was significant.

Many years later a reason occurred to me. Having different sizes on the end of an axle is to the car like going around a slight curve all the time. The greater the size difference the bigger the effect.

I have read that on some all wheel drive cars such a performance Audi's it is recommended that all four tires should be replaced if one goes bad and the tires have some miles on them. I guess this is because the all -wheel drive is sensitive to wheel diameter. I guess it is cheaper to replace the tires than damage the all wheel drive system.

I really do not have an answer for you. What you could do is run a measure tape around the old tire and the new tire. If there is much difference then begin to worry. If you have a locking rear end that likely can make a difference.

Are the front tires a different size than the rear?
 

m3incorp

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OP said he is getting the exact same replacement tire, so the above does not fit his situation. OP measure the tread depth of your good rear tire, depending on if you have done burnouts or not, you may find that it is at 8/32 or so in tread depth and the new tire will be about 9/32 or so. In that case, it should not be a problem.
 

sk47

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OP said he is getting the exact same replacement tire, so the above does not fit his situation. OP measure the tread depth of your good rear tire, depending on if you have done burnouts or not, you may find that it is at 8/32 or so in tread depth and the new tire will be about 9/32 or so. In that case, it should not be a problem.
Hello; I was not clear enough I guess. It is the difference in radius between the old and new tire that maybe a problem. Your suggestion about measuring tread depth should give an idea of the size difference.
 

br_an

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The owner's manual does say "It is recommended that the two front tires or two rear tires
generally be replaced as a pair. "

If it were me, I'd probably replace both rears (at least) to avoid an imbalance.
 

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m3incorp

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The owners manual most likely assumes that both tires have worn the same. He only has 9k on the tire so it MAY NOT be as worn as we might think. That is why I suggest measuring the tread depth.

The used tire places make a killing selling these slightly used tires.





The owner's manual does say "It is recommended that the two front tires or two rear tires
generally be replaced as a pair. "

If it were me, I'd probably replace both rears (at least) to avoid an imbalance.
 

br_an

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The owners manual most likely assumes that both tires have worn the same. He only has 9k on the tire so it MAY NOT be as worn as we might think. That is why I suggest measuring the tread depth.

The used tire places make a killing selling these slightly used tires.
He said nothing is mentioned in the OM, I am just pointing out that it does say in general replace as a pair.

A tire with 9k miles on it will definitely have the tread worn more than a new tire, and that's going to cause an imbalance - How much of an imbalance will depend on the amount of wear.
 
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its_me_walt

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Hey folks just picked the car up and its BAAAAAAD. ordered tire for other side.

entire car pulls violently right when accelerating. and it isnt alignment, drives fine when not accelerating

so lesson learned!
 
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its_me_walt

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now the question is am i damaging the diff? i may park until i get it sorted
 

br_an

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now the question is am i damaging the diff? i may park until i get it sorted
I wouldn't drive it like that. Better to wait for the new tire than damage the drive train or get into a dangerous situation with the car pulling to the side under acceleration.
 

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m3incorp

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If it is that bad, I would park it. Are you getting on it hard when accelerating? I wouldn't think it would pull that hard to one side with normal driving unless that tire is really worn down. If 9K took it down that far, I would have it checked out.
 
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its_me_walt

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it only pulls to one side under somewhat heavy acceleration . Not normal driving
 

m3incorp

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If you have a second vehicle, no need to risk it if you are worried. I hate to think our Mustangs are so sensitive that normal driving on a tire that has slightly less tread would harm it.
 
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its_me_walt

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In any case, hope someone finds this thread helpful and I appreciate everyone’s input.
 

sk47

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it only pulls to one side under somewhat heavy acceleration . Not normal driving
Hello; if you have an open differential the likely hood of damage is small for a few miles. Not sure how a posi or locking diff would be affected. My guess is the new tire has better traction and that may be part of it and the size difference may be the smaller factor. I really do not know for sure but the decision to park it until another new tire is on likely will be the best.
Good luck
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