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Old 12-04-2013, 12:55 AM   #1
Punk In Drublic
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Default Tolerance for difference in treadwear

it's that time of year again, the Blizzaks are going back on the wrx in a couple weeks. one tire developed a bulge last winter, but since they're a relatively new set of tires, I only replaced the bulged one. the new tire arrived via tirerack today, and I measured its circumference vs. the other three (used) tires.

the brand new one has a circumference of 78.0 inches, while the other three are all either 77 3/8 or 77 5/8 inches. should I have the new one shaved down or is it within our cars' tolerance for tread depth difference?
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Old 12-05-2013, 01:38 AM   #2
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I believe the tolerance is +-3/16" (.1875") circumference. I've known some people who have just increased the pressure on the "smaller" tire, but .375-.625 is quite a ways beyond that tolerance. I would try to get it shaved.

If you do put it on, put it on one of the fronts since that's an open diff.
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Old 12-06-2013, 07:06 PM   #3
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just spoke to my mechanic, who I consider to be the end-all-be all of subie knowledge, and he didn't seem to think it would be bad to just install with the other three, though he did suggust putting it in the back because of the open differential. my gut was saying put it on the front so it'll be worn down faster but he does have a good point. glad I still have a few weeks to decide...

edit: wait, so the front is an open diff. too?

Last edited by Punk In Drublic; 12-06-2013 at 07:30 PM.
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Old 12-06-2013, 07:48 PM   #4
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Quote:
Originally Posted by Punk In Drublic View Post
just spoke to my mechanic, who I consider to be the end-all-be all of subie knowledge, and he didn't seem to think it would be bad to just install with the other three, though he did suggust putting it in the back because of the open differential. my gut was saying put it on the front so it'll be worn down faster but he does have a good point. glad I still have a few weeks to decide...

edit: wait, so the front is an open diff. too?

Front is open - rear is LSD.
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Old 12-06-2013, 09:55 PM   #5
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how does limited slip vs. open differential play into the choice of where the new tire should go? obviously I'd just it shaved but no one seems to know of anyone who does that around here...
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Old 12-07-2013, 01:09 AM   #6
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Tires are most commonly measured in 32nds.

That being said, 2/32'' is the most difference I would advice; I work as a tire tech.
So if the new tire has 10/32'' new, all the other tires should be 8/32'' or more. If the difference is more, you may or may not be able to get away with it. I see it all the time where people come in with bald front tires and the rears have 6/32'' of tread. Some of the transmissions whine/grind, others have no problems. It is a hit or miss, but at your own risk over the 2/32'' mark.

Take the tires and have the tread depths measured at their lowest spots, go from there. If the difference is more, you can try it out and risk it, or sell the 3 and buy a new set of 4.
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Old 12-07-2013, 02:40 AM   #7
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Why not just get the new one from the Tire Rack and have them shave it to match.
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Old 12-07-2013, 02:58 AM   #8
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Already has the new tire. Read OP
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Old 12-07-2013, 01:21 PM   #9
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Already has the new tire. Read OP
I don't know how I missed that! Duh!!!

He could have had the Tire Rack shave it for him.
Perhaps the OP should see how much of a pain an exchange would be. Or go to his local chapter on here and ask if there is a shop that can shave it.
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Old 12-08-2013, 05:44 PM   #10
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I'm too having an issue where my front two tires are bald and it's time to change them seeing as I never rotated them and also put 20 k miles without doing so. The rear tires tread are in great shape but I've heard of the tranny issues if all four are not changed at once. With the open diff in the front would it be at all possible to get away with putting two front tires on now and purchasing the rear like two weeks later? Also I don't know hat the circumference difference is either.
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Old 12-08-2013, 07:00 PM   #11
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Originally Posted by Rawpowa89 View Post
I'm too having an issue where my front two tires are bald and it's time to change them seeing as I never rotated them and also put 20 k miles without doing so. The rear tires tread are in great shape but I've heard of the tranny issues if all four are not changed at once. With the open diff in the front would it be at all possible to get away with putting two front tires on now and purchasing the rear like two weeks later? Also I don't know hat the circumference difference is either.
You should get your alignment checked.

If we're talking a difference of a couple of weeks, just do them all at the same time.
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Old 12-13-2013, 08:02 PM   #12
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Quote:
Originally Posted by Punk In Drublic View Post

the brand new one has a circumference of 78.0 inches, while the other three are all either 77 3/8 or 77 5/8 inches. should I have the new one shaved down or is it within our cars' tolerance for tread depth difference?
That's a 1% difference in diameter, and thus a 1% difference in rotational speed. At 100mph your tire undergoes ~46 revs/sec. So the differential would see a 0.4 revs/sec difference. Isn't it negligible?
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Old 12-14-2013, 03:24 PM   #13
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Quote:
Originally Posted by Bluefoton View Post
That's a 1% difference in diameter, and thus a 1% difference in rotational speed. At 100mph your tire undergoes ~46 revs/sec. So the differential would see a 0.4 revs/sec difference. Isn't it negligible?
I don't really know what it mean practically, but it seems to me like almost half a revolution of the differential "differentialling" every second adds up pretty quickly.

The counterpoint is that we don't just drive our cars straight all the time so pretty much our differentials are working ALL the time...

I added no facts to the discussion
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Old 02-25-2014, 03:55 PM   #14
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I need to buy a Conti ExtremeContact DW as I punched out the sidewall on one. Can they be ordered shaved from Tirerack.
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Old 02-25-2014, 04:51 PM   #15
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I just had one of my blizzaks punctured and is done. The current ones have about 12,000 miles on it over 3 winters... Do I have to buy 4? or can i get two and put them both together on front or back? get the one and shave it down? recommendation?
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Old 02-25-2014, 05:23 PM   #16
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Quote:
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I need to buy a Conti ExtremeContact DW as I punched out the sidewall on one. Can they be ordered shaved from Tirerack.
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Old 02-27-2014, 12:11 AM   #17
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Quote:
Originally Posted by Garandman View Post
I need to buy a Conti ExtremeContact DW as I punched out the sidewall on one. Can they be ordered shaved from Tirerack.
Do not I repeat do not!!!!!!!!!!! Have tire rack shave 1 tire to match tread depth..........

Have them measure OD and shave accordingly if it needs it.

I bought a new DWS tire when my tires were @7/32 left. The shop didnt even have to shave it since it was 1/5th of an inch bigger than all the others.......

If they based it on tread depth they would have shaved 4/32 of tread off.

I had custom alignment do the work. They wouldnt lie to me since I took it in for something they do and they said it didnt even need it.

Be warned! Or Risk frying your center diff!
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Old 02-27-2014, 12:12 AM   #18
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Quote:
Originally Posted by Bikelok View Post
Why not just get the new one from the Tire Rack and have them shave it to match.
Bad advice unless shaving race tires. See above post!
Very strongly advised against. Even by custom alignment. Dave will tell ya.

Even tho bikelok gives some of the best suspension advise in the bay area for not being part of a performance shop!
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Old 03-16-2014, 09:05 AM   #19
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Ordered two from TR and then we'll go from there. Two of the tires have minimal treadwear so it should sort out.
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Old 03-17-2014, 07:44 PM   #20
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Quote:
Originally Posted by Scoobiesdoobies View Post
Do not I repeat do not!!!!!!!!!!! Have tire rack shave 1 tire to match tread depth..........

Have them measure OD and shave accordingly if it needs it.

I bought a new DWS tire when my tires were @7/32 left. The shop didnt even have to shave it since it was 1/5th of an inch bigger than all the others.......

If they based it on tread depth they would have shaved 4/32 of tread off.

I had custom alignment do the work. They wouldnt lie to me since I took it in for something they do and they said it didnt even need it.

Be warned! Or Risk frying your center diff!

Are you saying that you replaced ONE tire and did not have it shaved? You left it at what I am assuming is 11/32" (based on you stating they would have shaved off 4/32" and the others being at 7/32")?

Having the tires at the same Tread Depth should not fry the center diff or are you saying that having ONE tire at more than 2/32" could potentially do that?
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