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Old 12-12-2011, 03:45 PM   #1
Substi555
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Default AWD TIRE TREAD !!!!! please help

HELLO, I have an 05 STi and was just wondering since i got a flat on the rear driver side tire. I am wanting to replace it with a used tire that im picking up later this week. It is going to be the same size as the others 225-50-17. But it might be a diff. brand and tread pattern is that going to be bad for my transmission or diffs? just wanted some insight so any would help thanks.
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Old 12-12-2011, 03:51 PM   #2
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Tires of different brands can have different physical dimensions when compared to the same sizes.

A different amount of wear on one tire is enough to be bad.

Don't do it.

Don't believe me? Search and you'll see that this has been covered many times.
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Old 12-12-2011, 03:56 PM   #3
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what if the tire is about the same worn as all the others just a different tread pattern?
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Old 12-12-2011, 03:59 PM   #4
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Quote:
Originally Posted by Substi555
what if the tire is about the same worn as all the others just a different tread pattern?
Physically measure the circumference. If It's more than 3% off, don't use it.

How long are we talking about using it?

Short term, probably ok.

Long term, wear rates will be different so no good.
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Old 12-12-2011, 04:08 PM   #5
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about a year or alittle less? is that too long? thanks for the help tho
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Old 12-12-2011, 04:10 PM   #6
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Quote:
Originally Posted by Substi555
about a year or alittle less? is that too long? thanks for the help tho
Way too long.
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Old 12-12-2011, 04:18 PM   #7
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looks like this guys goin to be buying 4 new tires then.....AHHHHHHHHHHHHHHHHHHHHHHHHHH
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Old 12-12-2011, 04:20 PM   #8
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Do NOT get a used tire. It is used for a reason and also you risk damaging your AWD/Center diff!

Whenever you have to replace a tire on a Subaru, you must measure the circumference of the new tire when it is mounted. Then you measure the old tires. If there is more than a 1/4 inch of difference in the measurements, you should replace the other tires.

Do NOT let the 1/32nds or 3/32nds or any percentage rule fool you. That is not the correct method and it will cost you transfer clutches. Normally the 1/4inch threshold is around 15,000 miles, but I have seen a few make it to 19,000 and still be within 1/4 inch.

If you do not do this, you are increasing the chances of damaging the transfer clutches/center diff or prematurely wearing them out on your awd. Automatics tend to be more prone to this than manuals. It isn't really a matter of if it happens, but more of a when.
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Old 12-12-2011, 04:35 PM   #9
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so ur saying put a measurein tape around the tire on thr tread part and measure it and if they come out more then 1/4th then no good? please give an example thanks =)
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Old 12-12-2011, 05:06 PM   #10
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You place the measuring tape around the center part of the tread and record the overall circumference. Then you do the same thing to the 3 other old tires. Compare the results. If there is more than a 1/4 inch difference among all the readings, get 3 more new tires.
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Old 12-12-2011, 05:18 PM   #11
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ok thanks man i will do that, u might just have saved me some money GRRRRREAT!
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Old 12-14-2011, 01:09 PM   #12
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What are the symptoms of a trashed center diff? I just picked up a used 06 WRX and discovered that the front tires don't match the rear, in brand, or in treadwear. The front tires have more tread but the rear ones appear to be larger (in diameter, didn't measure circumference yet). The car only has 77k on it, but I'm certain thousands of those miles were with this tire combo.

My reasoning at the moment goes something like this:
Either my diff is trashed and it doesn't matter what I do, or my diff is fine, and clearly the tire combo is close enough to normal that it hasn't hurt anything. Am I crazy?

How do I know if the diff is ok?
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Old 12-14-2011, 01:51 PM   #13
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Go to a parking lot

Turn steering wheel to the right almost full lock

Accelerate slowly

If your car did anything but drive your centre diff is borked.
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Old 12-14-2011, 01:59 PM   #14
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Originally Posted by I come from honda View Post
What are the symptoms of a trashed center diff? I just picked up a used 06 WRX and discovered that the front tires don't match the rear, in brand, or in treadwear. The front tires have more tread but the rear ones appear to be larger (in diameter, didn't measure circumference yet). The car only has 77k on it, but I'm certain thousands of those miles were with this tire combo.

My reasoning at the moment goes something like this:
Either my diff is trashed and it doesn't matter what I do, or my diff is fine, and clearly the tire combo is close enough to normal that it hasn't hurt anything. Am I crazy?

How do I know if the diff is ok?
First: replace all four tires with either 215/45-17 or 225/45-17 (this presumes you have the OEM wheels).

By doing so, you will now be assured that you have four equally sized tires on the car and thus a point of reference.

Then: hope for the best regarding the differentials.

You may want to consider servicing the car (e.g. all fluids, belts, plugs, etc.) because it sounds as if this car has had no TLC.
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Old 12-14-2011, 02:11 PM   #15
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Originally Posted by Big-E View Post
First: replace all four tires with either 215/45-17 or 225/45-17 (this presumes you have the OEM wheels).

By doing so, you will now be assured that you have four equally sized tires on the car and thus a point of reference.

Then: hope for the best regarding the differentials.

You may want to consider servicing the car (e.g. all fluids, belts, plugs, etc.) because it sounds as if this car has had no TLC.
Thanks, I felt the same about it. I did the plugs yesterday, the rear diff fluid the day before, and I'm doing the tranny fluid and oil today. Do you really think it's necessary to do the belts? I thought they were good till 100k. I'm only at 77k now.

Still on OEM wheels (curbed to hell) but I'm planning on getting a second set so I can have a set for summer and a set for winter. I'm stalling on tires since the car is on jacks and I'd hate to just trash these tires and I haven't decided on whether I want the summer tires on my OE wheels or on aftermarket. Essentially determines what AutoX class I'll be running in, which I haven't yet decided on yet either. I want to run mostly stock, which pushes me towards the tire classes, but nobody in the subie crowd seems to be able to resist the modification itch, and I've had that rash in the past...
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Old 12-14-2011, 02:13 PM   #16
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Quote:
Originally Posted by Psychoreo View Post
Go to a parking lot

Turn steering wheel to the right almost full lock

Accelerate slowly

If your car did anything but drive your centre diff is borked.
Thanks for the tip, I'll try that. The other test I'll be performing today is to drain the fluid and look for PIECES!
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Old 12-14-2011, 05:49 PM   #17
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Originally Posted by I come from honda View Post
Thanks, I felt the same about it. I did the plugs yesterday, the rear diff fluid the day before, and I'm doing the tranny fluid and oil today. Do you really think it's necessary to do the belts? I thought they were good till 100k. I'm only at 77k now.

Still on OEM wheels (curbed to hell) but I'm planning on getting a second set so I can have a set for summer and a set for winter. I'm stalling on tires since the car is on jacks and I'd hate to just trash these tires and I haven't decided on whether I want the summer tires on my OE wheels or on aftermarket. Essentially determines what AutoX class I'll be running in, which I haven't yet decided on yet either. I want to run mostly stock, which pushes me towards the tire classes, but nobody in the subie crowd seems to be able to resist the modification itch, and I've had that rash in the past...
The timing-belt is serviced every 105,000 miles. The Alternator & Power-steering belt and the Air-conditioner belt are serviced usually much sooner. You would have to inspect each for general wear, cracks, fraying, etc.

If you're in a snow-belt area, put snowtires on the OEM wheels. Otherwise, put a decent set of tires on them and then save for a good set of high-performance summer-only tires and an aftermarket set of wheels.
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Old 12-15-2011, 09:17 AM   #18
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Oh great, now I actually have to make a decision. I finally did measure the circumference of my tires, and despite being different brands and different tread depths, they measured up to within 0.1" of each other. Now I am extremely tempted to just let it ride. I'll be buying winter tires when I move back to Seattle in about 1.5 months anyway, so I'm not sure if it's worth it to rush to replace these.
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Old 12-15-2011, 02:15 PM   #19
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Quote:
Originally Posted by Psychoreo View Post
Go to a parking lot

Turn steering wheel to the right almost full lock

Accelerate slowly

If your car did anything but drive your centre diff is borked.
Could you elaborate more on this as I have often wondered how you could tell the center diff was bad. When I bought my 2006 2.5i, the front tires had very low air pressure in them compared to the back. I replaced all 4 tires very soon as the tires were in bad condition.
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Old 12-15-2011, 02:20 PM   #20
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Could you elaborate more on this as I have often wondered how you could tell the center diff was bad. When I bought my 2006 2.5i, the front tires had very low air pressure in them compared to the back. I replaced all 4 tires very soon as the tires were in bad condition.
I would assume what he means is, if your car makes weird noises or doesn't move, the center diff is bad. However, weird noises could certainly be half shafts, and I'd be surprised to hear that the center diff failing completely immobilized the car, so take my idle speculation with about a pound of salt.
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Old 12-15-2011, 02:22 PM   #21
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Also, isn't it entirely possible that the diff would simply be damaged rather than destroyed, resulting in reduced performance? It is a viscous coupling isn't it?
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Old 12-15-2011, 03:17 PM   #22
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yes, it is vicous coupling, that is why I am wondering how you can tell if it is damaged. Does the center diff just control the amount of power going to the front and rear diffs?
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Old 12-15-2011, 07:50 PM   #23
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When the AWD is going bad and when driving slow while turning you will feel as if the car is fighting you while trying to turn. It is like a pulsation but worse and you won't miss it. It is very obvious. The center diff controls the transfer of power from the front and rear differentials.
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Old 12-16-2011, 09:22 AM   #24
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This effect is only noticeable when going slow? I have precisely this effect while at speed, but I keep forgetting to try it at low speeds. I think my steering pulsing/fighting effect is due to air in my power steering system though. Gosh I sure hope so.

How different is the sensation from a power steering malfunction?
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Old 12-16-2011, 11:23 AM   #25
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This effect is only noticeable when going slow? I have precisely this effect while at speed, but I keep forgetting to try it at low speeds. I think my steering pulsing/fighting effect is due to air in my power steering system though. Gosh I sure hope so.

How different is the sensation from a power steering malfunction?
Power steering should only have an effect while turning the wheel. If the wheel is turned held, the power steering pump has no effect.

If the car is pulsating, jerking, or binding in low speed turns (think pulling into a parking spot after stopping first) It's likely a bad diff.
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