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Discussion Starter #1
Hi,
I just replaced one michelin harmony tire which I had a screw in!!! I measured the difference between the new one and the old ones and it's 3/32. I'm screwed aren't I? From what I can find, subaru says no more than 2/32.
Thanks,
Brian
 

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#8 Post ho
1999 Subaru Forester
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Well.. it is very important to have all uniform tires.. tho, I'm not sure what allowance there is
 

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2004 fxt
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volman said:
Hi,
I just replaced one michelin harmony tire which I had a screw in!!! I measured the difference between the new one and the old ones and it's 3/32. I'm screwed aren't I? From what I can find, subaru says no more than 2/32.
Thanks,
Brian

try to find someplace to shave the new tire.
 

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2004 Forester XT Premium 4EAT
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Measure the rolling circumference on the tires. IIRC, it's not supposed to exceed 1/4".
 

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2018 2.5i Premium CVT
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Yes, the spec is 1/4" circumference, which works out to just over 1/32" radius, i.e. tread depth. I have a hard time believing that this is even within manufacturing tolerance, let alone the difference one might see between front and rear just before it got time to rotate the tires.

Personally I think the spec was written by the lawyers.

I've cheated twice by a few 32nds and my Forester is still happy at >75k miles.
 

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volman said:
Hi,
I just replaced one michelin harmony tire which I had a screw in!!! I measured the difference between the new one and the old ones and it's 3/32. I'm screwed aren't I? From what I can find, subaru says no more than 2/32.
Why did you replace it instead of patching it?

How did you measure it?
 
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Discussion Starter #7
Thanks for the replies. I had to replace it because the screw was in the
sidewall. Ughhhh....I measured it using a tire depth gauge.
 

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volman said:
Thanks for the replies. I had to replace it because the screw was in the
sidewall. Ughhhh....I measured it using a tire depth gauge.
Okay, I understand. If it is the same brand/model as the other 3 tires, then that is a reasonable way to measure it, but it has quite a bit of error in the measurement. Rolling the car through a complete tire rotation and noting the differences between the tire circumference would be a better way to do it. Make sure that you have the same pressure in all the tires.

How many miles on the other 3 tires?

BTW, this is one of the reasons why I have 5 matched wheels, buy tires 5 at a time and do 5 tire rotations. If I end up in your situation, I can buy a new tire, keep it as the spare, and revert to a 4 tire rotation pattern. I realize this is no help for you now, but something to consider in the future.
 

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Ah crap.. I'm back with my 05 XS
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hmm.. you should always have a set of 5 tires like mtnbiker said. i ran into a crazy driver and had to replace a tire because of her and luckily i had my 5th and barely any difference in size at that time but if i did, i would've just shaved the single replacement.
 
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Discussion Starter #10
Thanks for the tip Mountain Biker, the 5 tire rotation is a great idea. I bough the car used and the tires were already on it so I'm not sure how many miles are on them. The Harmonies are a long life tire (80k) and the car now has 76k on it. The spare is a worn out bridgestone dueller.
What is the best way to measure the circumference? Mark each tire and roll the car one tire turn?
 

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volman said:
What is the best way to measure the circumference? Mark each tire and roll the car one tire turn?
That sounds like the best way to me.

The problem is, how close is close enough? Subaru says 1/4" maximum difference in circumference. Lots of internet experts say that is not necessary. You have to decide whom to believe!
 

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One more tip. When measuring the circumference, no matter how you do it, take the measurement several times use the average. Also make sure there isn't too much difference between each measurement as validation that you have a good process.
 

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2002 Forester L
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You're on a open diff, should be ok if all measurements are reasonably close. I have run 3 different brands of tires at one time (with different wear, two on the front are the same) for quite a while without any issue. This is another myth that tire shops (or dealers) want to scare you. You DO have to remember that your handling will be compromized a bit (braking/cornering), but in no way this will harm your tranny/diff. Every time you make a turn, you're putting much much more stress on your diffs. When tire sizes are slightly off, it's like you're driving slightly curved course (to the diffs) all the time. Now subies can run around tracks all day with no problems, right ? ;-)
 

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Is this the same as the older land rovers? You used to have to unwind the transmission occassionally by reversing 100yards.... They were awd in 1955.

Using an SF off road would be no problems surely. Each transmission corner/wheel would spend random moments in the air. Any tension in the transmission would be negligable. Driving on a hard and even road surface in a straight line would be worse?

Anyone had transmission problems due to tyre/tire differences in size?
 

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andrewhg said:
Is this the same as the older land rovers? You used to have to unwind the transmission occassionally by reversing 100yards.... They were awd in 1955.

Using an SF off road would be no problems surely. Each transmission corner/wheel would spend random moments in the air. Any tension in the transmission would be negligable. Driving on a hard and even road surface in a straight line would be worse?
The Subaru awd doesnt 100% lock the diff, so you dont have worry about windup.
What you do have to worry about is heating up the fluid in the centre diff. The viscous system relies on this heat up to lock the diff tighter, but you dont want it to lock it tighter if each end is forced to turn at different rates, since this will just make the problem worse.
 

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Noted. Cheers.

In the thread 1 Lucky Texan blokey pointed out that

"keep in mind, if you do have to buy tires a little sooner than you'd like, it really isn't a total waste - you're getting NEW tires! And, with AWD, you likely would have better performance with cheap tires than a 2WD car with expensive tires. So just get 'value' tires and rotate them"

I like that idea, just bought a used Forester and have spotted difference in wear between treads already. These are Bridgestone ???? All match tho.

Anyone in the UK use "value tyres?", I know there is a place near the Belfry golfcourse called 4x4 tyres. Anyone used it?

Andrew
 
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