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My wife hit a curb in my 2012 Subaru Impreza and there is a small tear in the tread. Do I need to replace all 4 tires or can I just replace 2? I was told that I may have to replace all 4 tires because it is all wheel drive and to do otherwise may damage the transmission, but the person was not sure. The tires are less than a year old and it seems like such a waste to replace all 4. Is it necessary?

tire tear

As I was doing the penny test I noticed a second tear in the sidewall so the tire need to be replaced for sure. And unless I'm doing the test wrong it looks like the tread is low anyway so I'll probably replace all 4.

  • possible duplicate of Replacing tires for 2001 Subaru Outback – Pᴀᴜʟsᴛᴇʀ2 Jul 11 '15 at 17:29
  • Thank you Paulster2 that link was informative but is focused more on changing the tire size/shape. My question is more general. Because the 2012 Impreza is All Wheel Drive do I have to replace all 4 tires (they will be all the same type) or can I replace 2 tires (the damaged tire and the tire opposite it) without worrying about damaging the transmission – Brian Jul 11 '15 at 17:43
  • Sorry I grabbed the wrong one .. it should have been this one ... that's what I get for not reading the entire question/answer, lol! I hope it helps. If this does not answer you question, please let me know. – Pᴀᴜʟsᴛᴇʀ2 Jul 11 '15 at 17:55
  • Also, if you only have a small tear in the tread, there is no bulging, out of round, or air leakage, I'm not so sure I'd worry about it. It all depends on your comfort level, but for the most part if the damage is small enough, there should be no worries about replacement. – Pᴀᴜʟsᴛᴇʀ2 Jul 11 '15 at 17:59
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    Bonus points if you provide pictures if the issue. Double bonus if you stick a Lincoln penny into the tread block grooves and provide that as well. – Bob Cross Jul 11 '15 at 19:11
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What I said over here might apply to your situation:

... a mismatched tire won't break your drivetrain immediately. It's more subtle than that: at least one differential will be loaded all of the time and at all operating speeds. So, instead of managing the different rotation speeds in a relatively low speed turn, you'll be cooking your differential at highway straight line speeds.

Now, your situation might not be the same. Here's how to tell:

  1. How bad is the tear? Did it chip one of the tread blocks? Or is it effectively through the tire and causing a leak? If more that a chip and less than a tear, how worried are you?

  2. How worn is the tire? How much tread has been used up? Can you even tell that the tires have been used? Or can you see all of Lincoln's face?

In the end, if you are talking about super worn tires, you should replace the set. If they're barely touched, you might be able to get away with just replacing the one. Somewhere in between, you might be able to replace the front pair. You're going to have to make the call.

That said, you should listen for the audible symptoms of a stressed differential:

you can hear the differential being overworked if you listen for it. On my Subaru, if I inflate the rear tires to match the front tires' pressure (approximately 4 psi up), I'll hear a distinctive high-pitched whine from the center differential every time I coast down from speed in second gear.

As I said before, my WRX and your Outback are not the same car. However, the vehicle will try to let you know if there's a real problem prior to total system failure....

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tire tear

As I was doing the penny test I noticed a second tear in the side wall so the tire need to be replaced for sure. And unless I'm doing the test wrong it looks like the tred is low anyway so I'll probably replace all 4. Thank for all your help.

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    For those flagging this as "not an answer", it clearly is the answer to the original question. Yes, the tread is worn and, yes, there is additional damage to the tire that recommends replacing all the tires. I, the mod, have spoken. – Bob Cross Jul 12 '15 at 15:18
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In the UK we have tyre fitters that specialise in Part Worn tyres. If you have similar in your local area then it would be worth asking them to measure your remaining tread and see if they have a suitable replacement tyre instead of having to buy a full set. That's certainly what I would try first.

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Take a measuring tape and wrap it around your tires. Then wrap it around one of the potential new tires. If the circumference of the new tire is within 1/4 inch (6mm to 7mm) of the others, don't worry about it.

You may also have a bit of luck looking at the local classifieds section. Sometimes people sell off tires with a good bit of tread left on them when they buy new alloys or a set of performance tires.

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