Worn Tires damage Diff's?

I bought a set of Michelin Pilot Sports off of a buddy that are 50% worn...trying to reduce the cash out of my pocket right now and see how I like them before I bought some. I couldn't believe he had the exacy size I wanted sitting in his garage, 225/45/17's. Had them on for 2 weeks and last night I punched a bolt through the centre of one of them. Picked it up on the highway at full speed, man did that make some noise as it banged into the wheelwell liner on every revolution:( .

 

I went to the tire shop today and the tire is toast, the bolt actually punched a plug of rubber right out of the tire rather than sliding through like normal. Problem is that with the tires 50% worn already I can't really replace one side only so I have to buy at least two. Question is, to avoid any potential damage to the centre dif do I have to replace all 4? I would assume so.

 

The tire shop is going to try and get michelin to give me road hazard replacement (pro-rated to 50%) on all 4 tires...they have done it before but can't garantee it will go through. They will cover it if possible because I have bought a couple other sets of tires there and so has my buddy that sold me these. If not I'll just buy something cheaper (BFG KDW2's look like a good option).

 

Thought I had gotten lucky and saved some cash by getting some used ones but instead I just cost myself a pile because had they been new I could have just replaced one:mad: .

The Legacy uses a viscous type limited slip. Any difference in tire speed rotation will cause the fluid in the differential to heat and the cluth discs will start to compress. The only question is how much tolerance Subaru has built into the system. My guess is that you'd probably be okay, but I would try to match the tire sizes if at all possible. Better to spend the extra money on new tires than a new differential.

The rule (according to Subaru), is no mre then 1/4" difference in circumference, which is really not much.

You'll be ok.. it's when you get some really big differences like two different tire makes of the same size whre one is clearly larger than the other. But since you have the same tire make and plan to replace with the same tire model and size, you'll be ok.

 

Keefe

Call Atlantis Tire @ (310) 538-3528. They have a ton of used Pilot Sports in 225/45/17 and they do ship (from Los Angeles). They import their tires from Germany, where the DOT laws dictate that tires get tossed when they show a certain amount of wear but they are actually in pretty good shape. They also sell on eBay.

The rule (according to Subaru), is no mre then 1/4" difference in circumference, which is really not much.

 

sduford is correct...it's also in the Owners Manual

Another option is to measure the tread depth and have a new tire "shaved" down to size. I realize this option stinks, but right now its cheaper than 4 new and you get to experience the Pilots like you wanted to. They would do this with a trueing machine normally used for out of round tires.

Not a bad idea...I was considering breaking out the belt sander. I'm still looking for a used one locally but may resort to getting one shipped up if need be.

Anyone notice how much tire pressure makes a difference in actual circumference? It's quite a bit. Besides, a fraction of a degree, per revolution? It's gotta have more tolerance than that.

Who knows, they may be understating the tolerance to protect themselves from claims should something go wrong.

Well I found two used ones locally with 7/32 tread remaining. Mine are at 5/32 so I'll likely just swap them both onto front or back. I can't see 2/32" destroying a dif. If I use them on the back the 2psi less pressure I run back there will likely compensate anyway. Thanks for the suggestions guys.

2/32" is within the allowed tolerance of 1/4". Sounds like you'll be just fine.

2/32" is within the allowed tolerance of 1/4". Sounds like you'll be just fine.

circumference vs tread depth.. hmmm.

circumference vs tread depth.. hmmm.

 

Thanks, I wasn't paying attention.

 

Is it really circumference though? That's a pretty small difference if so. I'd of expected it to be diameter, then 2/32 tread difference would be 1/4" diamter difference. (assuming equal sizes unworn).

I am in the same situation having to replace one tire due to a pothole. What if you replaced both tires on the axel. Would that work? So your two front tires would be the same diameter and the two back tires would be the same diameter (although front to back would be different). I don't think it would work, but just a thought....

2/32 actually works out to be more than 1/4" difference in circumference...0.39" IIRC.

So what is everyone with 225/17’s and 18’s planning on doing if they get a flat?

Can I run a full size spare (215/25/17) for a few miles if all my other tires are 225/45/17?

in general it's true a limited slip diff will tend to hurt it self if one tire is even slightly smaller than the other tire on the same axle. It will in effect sense a slip or constant turning condition. HOWEVER, as I understand it our limited slip diff does not use clutch packs but rather the viscous coupling effect of a closed unit within the diff. As such there are no clutch packs to wear out, however you will tend to put more heat into the viscous coupling unit. Will that damage anything? I agree it depends on how much you're out of wack with respect to the other tire. With variations due to tire pressures, manufacturing tire tolerances, bearing differences, other material stack up differences, etc. I can't see Subaru putting such a tight spec on the tires. I will tell you however that all these deltas should balance each other out and almost never stack up all on one side of the diff.

So my conclusion, anything less than 1/8" I wouldn't worry about. If greater put the tire on the other side every tire rotation.

You won't damage it. Imagine driving in the mountains, and constantly turning all the time. That won't wreck your car.

with all due respect, the car is not made to turn all the time. That's the point. turning in the same direction all the time will wear things out much quicker. However, given the 5MT has an open front diff and the center and rear diffs are viscously coupled, nothing tragic will occur.

What is the stock spare tire? I dont think its close to the same size as the stock 17inch tires. How can we possibly use that if it were to cause damage?

I am in the same situation having to replace one tire due to a pothole. What if you replaced both tires on the axel. Would that work? So your two front tires would be the same diameter and the two back tires would be the same diameter (although front to back would be different). I don't think it would work, but just a thought....

 

The center diff would still experience a relative speed difference.

What is the stock spare tire? I dont think its close to the same size as the stock 17inch tires. How can we possibly use that if it were to cause damage?

 

The donut is picked to match and should only be used for a short time.

I remember the manual says if you have a flat you have to replace the flat tire with the spare and to move it on the back (or was it the front). And then plug the FWD fuse.

Good luck with fuse and MT.

 

Krzys