Tire Circumference Again - FWD helps?

[vtphoto]

Hey folks,

 

I recently developed a leak in one of my tires on my 2000 Outback wagon, and had it replaced under warranty. The leak was in the sidewall and could not be repaired.

 

I've read extensively the threads on having all your tires close in circumference... and it seems like there is some difference in opinion in how strictly the recommended 0.25" Circumference difference should be followed.

 

The tire shop guys insisted that it should be fine... 1" is their limit on recommending all new tires.

 

My local mechanic, and my mechanic back home agreed that 1" is a safe limit.

 

My 3 older tires all checked out with a Circumference of 82 11/16 inches. All were exactly the same (I rotate every 4k miles, and have a lifetime alignment from Firestone that has paid for itself twice over now).

 

The new tire has a circumference of 83 7/16 inches.

 

This creates a difference of 0.75 inches.

 

Here's the deal... the ONLY place I know of that will shave a tire on-location is near Toronto, Ontario. I currently live in Illinois. I'll be visiting home (Vermont) in about a week, where I'll be driving right through Toronto.

 

Can I get by with this differential until next week? My commute to work is only 1 mile each way, and the distance to Toronto is about 650 miles.

 

The new tire has been mounted on the right rear. It seems like turning off AWD would be a good idea. Would doing this completely eliminate the entire risk where I could drive a bit more freely until I get up to Toronto next week to get the new tire shaved down?

 

The way I understand it, with the AWD shut off, the differential in the rear should not kick in at all, thus no problems right? (wrong?)

 

Another solution- Does anyone here know of any place in Central Illinois (or Saint Louis... or Chicago) that can shave a tire? I've asked around a bit, but keep getting blank stares. No one seems to know what the heck that even means, yet "shave the tire" is common advice on this forum. There's got to be some other places out there other than Tire Rack.com that can do it...

 

Thanks!

-Mike

[LosDiosDeVerde86]

no no..

 

it's should no more than 4/32nds of tread depth difference. That's from Good Year.

[vtphoto]

Tread depth difference is 3/32nds between the old and new.

 

no no..

 

it's should no more than 4/32nds of tread depth difference. That's from Good Year.

[Commuter]

With an automatic, I don't think I'd be comfortable with 3/4" difference.

 

Try calling performance shops, racing shops, places like that. You are not going to have much luck with tire shaving with run of the mill places.

 

Put the FWD fuse in and you'll be fine. This disables the center clutch pack. No power is sent to the rear wheels at all this way.

 

You could also slightly lower tire pressure in your new tire to reduce its rolling circumference. However, there are all the "cons" to running with low tire pressure. I'm not sure how much would be needed, but say, 5 psi lower would not be an issue to me. Bump up the other 3 a couple psi to create even more difference. But really, on the back with the fuse in, it won't matter. Your rear differential will work a bit, but nothing it shouldn't be able to handle.

 

I went thru this same issue a few years back, however, the wear on my remaining 3 was so little, that I had 1/4" or less in difference. Once I determined that, I took the fuse out and things were fine.

 

Good luck.

 

Commuter

[Commuter]

Note:

 

1 mm (which is less than 2/32nds) of tread depth equals 1/4" on the circumference.

 

1 mm = 0.040"

1/32 = 0.031"

 

Note - Conversions rounded slightly.

 

Commuter

[yohy]

vtphoto,

 

May be too late for you with regards to current situation, but in the future an FYI (I found this out after dealing with a similar situation). The Tire Rack has offered a tire shaving service, price will range from $25 to $35 for each tire. (http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=18)

 

Good luck.

[bjwirth]

all you're going to get are touchy-feely answers.... ie "i feel that 0.XXX inches is ok" or "I've heard anything over 0.XXX is asking for trouble" Other than a reference to the subaru manual, there's no data on this and more importantly there's no data to support CAUSATION- just corrolation.

 

I don't know what to say to you as to whether 0.75 inches is ok to drive on. (I think it's ok and this is based on pure touch-feely voodoo science) But I'll say this, if it bothers you so much that you're willing to drive all the way to toronto to have a tire shaved, I'd just buy 3 new tires and be done with it.

 

I think tire shaving is a waste of money. let's say you spend $50 to shave a tire and you get another 20k miles (or whatever) out of your old tires. Then you spend another $400 to get 4 new tires later. alternately, you could spend $300 on 3 new tires, sacrificing the 20k miles. Is the $150 worth the 20k miles? if you do the math, it isn't. let's say you get 50k miles out of your tires. on the shaved tire scenario, you'll spend $450 and get 20k + 50k = 70k miles or $450/70k= $0.00064 /mile. if you buy 3 tires, you get $300/50k= $0.00060/mile.

[vtphoto]

Well, I'm driving all the way to Toronto to get the tire shaved. It happens that I'll be driving through Toronto anyways, and was likely to stop there to check out the Hockey Hall of Fame too.

 

Normally I'd agree with the waste of money thing, but these tires have about 70% of their tread left on them, at least 50k miles. They cost about $110/ea, and the replaced tire was free. Four new ones = $440 (plus tax, road hazard plan... looking at $500). Considering I have about 70% of tread left on them, they are effectively worth $350. So, spend $30-50 to save $300-320... sounds OK at this point. If they were more worn down, then I'd certainly agree... just bite the bullet.

 

Bottom line is... it sounds like disengaging AWD should allow me to safely roll along for the next week or so until I get the tire shaved. Next time around... 5 tire rotation... (then 2 will go flat at once!)

 

Thanks for the advice.