Tire wear - Subaru WRX Forum
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#1 Old 01-05-2011, 01:56 PM
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Tire wear

So here is the quick background. I had an 04 WRX with 17” Rotas on it. The car is now gone and I have an 05 wrx. I am now using the same Rotas on my 05 WRX. I have Goodrich G force tires on the Rotas. The Rotas are only used in the summer.
OK, So I took my Rotas off the car and put on the winter rims and found that the driver side front tire was warn to the wires on the inside of the tire. With the winter rims on, I went to get an alignment on the car. When I got to the shop, they ran some tests and told me my car WAS aligned properly. So my question is what would cause the inside to wear like that? The car drove fine (not vibrations or pulling). Could it be something wrong with the rim? Could this problem have come for the previous car?
Thanks
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#2 Old 01-05-2011, 02:08 PM
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Did you go to a dealer or a pep boys or something? Do yourself a favor and drive into the city and take it to the best alignment guy in the state. His name is Jeff. He's cheap, but best of all he will match your specs. Tell him you want "all of the negative camber you can give me". That, along with actual zero toe (not 0.2 because the guy is too lazy to do his job) will fix your tire wear.

Jeff, the alignment guy

Seriously, a good alignment is one of the best performance mods you can do for your car. It will make the steering response better, the grip better, the suspension better, etc etc etc.

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#3 Old 01-05-2011, 06:50 PM
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Good point, I need to stay on top of that better.

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#4 Old 01-06-2011, 08:53 AM
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Yeah, me too.. I'll look in to that this summer.

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#5 Old 01-06-2011, 01:06 PM
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Quote:
Originally Posted by mosc View Post

Seriously, a good alignment is one of the best performance mods you can do for your car. It will make the steering response better, the grip better, the suspension better, etc etc etc.
Not really a mod, IMO, as you really should be putting the car back to factory spec, but I agree that a real alignment it totally worth spending your money on!

Related the the tire wear, if you've had that tire running under-inflated, then it will wear the sidewalls more than the center, and if you turn really hard one way under heavy acceleration/braking it's also possible to do that with a properly aligned car. When you turn, the wheels will actually lean by design but at different speeds this doesn't actually keep the biggest contact patch down. You'd have something pretty obvious that you do in your driving for it to be that sever though. I'd lead more toward the tire being a little under-inflated.

If it's due to the turn-tilt, it would be related to right hand corners.
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#6 Old 01-06-2011, 02:19 PM
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"factory spec" is too broad. It allows for massive toe which should be 0.0. The factory spec also doesn't allow for much negative camber which is incorrect. -0 camber, which is within spec, will decrease performance, steering response, and wear out the outer edge of your tire. "Factory Spec" is a meaningless vagary in the world of alignment which when you hear it should be a clear indication to take your car somewhere else.

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#7 Old 01-06-2011, 02:44 PM
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^Agreed. Good points.
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#8 Old 01-06-2011, 04:05 PM
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So Mosc,
I might be going to Bloomington this weekend. If I do, I will set up am appt with Jeff. I should tell him (or another shop if I dont make it to the cities) exactly what you wrote.
"all of the negative camber you can give me". That, along with actual zero toe.

Hondafan: I drive pretty conservative and check my tire psi at least 2 times a month.

Thanks for all the help and info!
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#9 Old 01-06-2011, 04:43 PM
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Hondafan: I drive pretty conservative and check my tire psi at every fill up.
Fixed

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#10 Old 01-06-2011, 09:04 PM
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Chris... Good fix!
Actually, I only fill up about every 2 weeks.
What psi should my tires have? The max (on the side of the tire) is 50psi so I usually try to keep it around 40. Should it be higher?
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#11 Old 01-07-2011, 10:34 AM
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That's too high. My max is about the same and I keep my fronts around 36 and rears around 34 and I rotate them front to back every other oil change and adjust the pressure accordingly. The front tires should be slightly higher than the rears because there's more weight up front - engine, duh. The rating on the sides of the tires are meant as a guideline for if your car is completely maxed out with people/cargo weight all the time. Under normal driving conditions, the pressures should be much lower or you'll end up with too much wear in the center of the tire tread due to overinflation. If you don't believe me, get a tire tread depth gauge and monitor the tread depth over time for different pressures until you find what works for you. Take measurements at the center of the tread, as well as at the inner and outer edge at various points around the circumference of the tire for the most accurate measurement.

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#12 Old 01-07-2011, 01:10 PM
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Quote:
Originally Posted by gunk007 View Post
So Mosc,
I might be going to Bloomington this weekend. If I do, I will set up am appt with Jeff. I should tell him (or another shop if I dont make it to the cities) exactly what you wrote.
"all of the negative camber you can give me". That, along with actual zero toe.

Hondafan: I drive pretty conservative and check my tire psi at least 2 times a month.

Thanks for all the help and info!
Note that Jeff is often booked far in advance so if you can, try to call ahead of time. Jeff will probably ask you how much camber you want to which I just replied "all of it". The WRX generally can't bet set past about -2.0 up front and -1.5 in the back. I mean, you probably don't want more than -2.0 but I doubt you'll have to worry about too much. To be fair when he did my STi it barely went to -1.0 in the front though the WRX does have a little more room to move.

As far as tire pressure, a good starting place is 85% of max in the front and 80% of max in the rear. You should play around with the pressure up and down to get your desired response. 40PSI on a 50 PSI max tire is fine, no issues. If the pressure is too low, say below 30 psi in your application, it can cause excess wear. Too much pressure will rarely result in tire wear, not on a street tire. Over inflation is dangerous though, it's a safety concern.

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#13 Old 01-07-2011, 03:31 PM
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Thanks for all the good info. I will try and get the exact specs up on here soon. I just got to get the paperwork. So what I am hearing is that the tire wear was probaly from what... alignment?
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#14 Old 01-08-2011, 03:06 PM
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Dunno. It's impossible to tell without information from an alignment specialist/tire specialist. It's still possible (not probable) to have a bad tire from the beginning which wore faster, and it's possible it's the alignment or air pressure.
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#15 Old 01-09-2011, 12:15 PM
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Yes, there are other causes for uneven tire wear. The tire could be defective, your suspension could be busted, or the tire could have improper mounting/balancing. However, the most common and least noticeable effects on your overall car would be non-zero toe and near-even or positive camber (aka bad alignment).

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