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Old 05-11-2008, 11:06 PM   #1
Scooby Newbie
Member#: 71108
Join Date: Sep 2004
Chapter/Region: SCIC
Location: San Diego, CA
2005 WRX STi

Default Tire wear symmetry question on 2005 WRX STi

I have a little problem: I have been running Goodyear Eagle F1 GS-D3 tires on my car for the last 18 months or so (I love them, by the way), and recently, I picked up a nail in one of my tires. It's on the shoulder of the tire, about 1inch from the sidewall, so my suspicion is that it will not be "safely repairable". It doesn't look to me like the nail damaged the sidewall, but my experience is that tire places are very conservative about this stuff, so they're probably not going to help me out.

So my question: Do I need to buy just one new tire? Or two new tires? Or 4? I'm concerned about the differentials.

I've been a good boy and have been faithfully rotating my tires front to rear to even out the wear. All of the tires have about 5/32" of wear left on them. (New F1 GS-D3 tires have 11/32" of tread depth according to Tire Rack). The new tire is 24.9" in diameter.

So replacing a single tire would mean a rotational speed difference of ((2*(6/32))/24.9 = 1.5%).

If I replace one rear tire, the rear LSD will be seeing a constant (albeit fairly small) difference in rotational speed. And the center diff will see a difference as well.

If I replace both rear tires, the rear LSD will be fine, but the center will see a difference.

It would be nice to get the extra 10000 miles of remaining wear out of the undamaged tires. But is it a good idea?

So I guess my question boils down to:
How much difference in rotational speed can the LSD in the rear tolerate on a continuous basis? How much front-to-rear difference in rotational speed can the center differential tolerate? I assume the only issue here is how much heat will be generated by the constant slip? Are there other issues?

I appreciate any helpful feedback here. Maybe I'm worrying about nothing, but some solid information on what's ok and what's not would help put my mind at ease.
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alanlcit is offline   Reply With Quote
Old 05-12-2008, 07:39 AM   #2
Scooby Specialist
Member#: 141672
Join Date: Feb 2007
07' wrx
Mothballed until winter


If the object is a thumbs width or more away from the edge where the tread starts, you can repair. Liability concerns combined with wanting to sell you a new tire is why shops are less prone to repair tires.

Many here have successfully plugged their own tires btw. The best way to do it is to dismount the tire and use a plug patch. You could get a plug kit and do it yourself easier then you think.

Used tire shops are more likely to help fix your tire. Those shops however like to scratch wheels.
mikeythejew is offline   Reply With Quote
Old 05-12-2008, 10:09 AM   #3
Scooby Specialist
Member#: 165744
Join Date: Dec 2007
Chapter/Region: Tri-State
Location: Eastern PA
2000 LGT
2007 STi


if it can't be repaired, you can always buy one new tire and have it shaved, but those tires are more than halfway done. otherwise, i'd replace all four, and hang onto the other three. either try selling them, or keep them around in case any of the new ones end up with a failure.

just out of curiosity, how many miles did you put on those tires to only wear off 6/32 in 18 months?
growling_boxer is offline   Reply With Quote
Old 05-12-2008, 07:18 PM   #4
Scooby Newbie
Member#: 71108
Join Date: Sep 2004
Chapter/Region: SCIC
Location: San Diego, CA
2005 WRX STi

Default Re: How many miles for 6/32" of wear

just out of curiosity, how many miles did you put on those tires to only wear off 6/32 in 18 months?
I've put 24000 miles on the tires. My driving style is: fairly fast acceleration frequently, but I try very hard to never use my brakes (use engine braking, don't come screaming up to red lights, etc...). I usually take corners pretty fast.

There was about 6-7k miles of long freeway road trips on those tires. A lot of my commute is on freeway. Not particularly hard on the tires.

Based on the above, I've probably got another 10k miles on them.

On the stock Bridgestone Potenzas, I got 33k. Looks like I would get a bit more out of the Eagle F1s, at least if I hadn't picked up the nail.

alanlcit is offline   Reply With Quote
Old 05-12-2008, 07:40 PM   #5
Scooby Specialist
Member#: 41070
Join Date: Aug 2003
Location: Arizona
2005 Black Tiger
(Black Turbo Baja)


Depending upon how you choose to look at it, consider this:

Tires are generally considered to be worn out when the wear bars show up or when you can see the top of Lincoln's head on a penny inserted upside down in the tread. That's 2/32". So, you really only have 3/32" left. Still, I'd run with Mikey's suggestion to try to get this fixed if you're ~1" inside the tread edge.

To answer your question directly: I don't know positively, but your owner's manual or the shop manual has (used to have) this information in it.
bulwnkl is offline   Reply With Quote

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