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Discussion Starter #1
I have one snow tire that needs to be replaced. The other 3 are good. I found a tire that is the same size and is only 1/32" different
in tread wear. Actually it is a newer (based upon DOT code) tire with 1/32" more tread then the other 3. Is it ok to use?
I heard that I have to be within 20% of the current tires tread depth?
DD
 

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2013 BRZ 2005 OBXT
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Tread wear is important dont get me wrong but what you need to be more concerned with is the actual diameter and width of the tire. Making sure that is as close as possible before even attempting it. That said I would not do it...
 

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2002 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
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NO. with whatever subaru you got, NO.

buy a single new tire that matches what you got exactly,
and have it shaved down by a big tire shop to match the depth of the other 3. (tire rack or discount tire online might do that too).
 

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06 OBW 2.5, 05 Forester, had 03 H6 OBW
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If you decide to try it you can run a quick easy test to check the matching.
You'll need an open space and a helper.

Park car at end of open space, wheels straight.
Mark each tire on sidewall where it hits the ground.
Have helper watch one tire.
Drive so any tire rotates 10 times, mark pointing straight at ground again.

The required match of .25 inches circumference match has now been multiplied to 2.5 inches around the edge of the tire, check all the chalk marks and compare the furthest-forward to the furthest-back.
 

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Lawn ornament XT
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It's all down to the tale of the tape. Put a measuring tape around your 3 healthy tires. Take the mean average of their circumference.

Then find a tire that matches (after mounting & inflation).

If it's a close match, you're good for now. Repeat the measurement periodically, maybe twice a season to see if it is still a match. Be ready (financially) to act immediately if they don't match due to differential wear over time.

If this sounds like a lot of work, just do it the right way.

There are two right ways- you can get a new tire shaved to match the other three at a specialty tire shop, or you can replace the set and sell 3 good used tires to recoup costs.

If that doesn't convince you, compare the cost of a set of tires to the cost of a new transmission. With great AWD comes great responsibility.

Edit: See above post. Strong endorsement of CNY's method, just as good as a measuring tape with less effort.
 

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2017 2.5i Premium Lapis Blue
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I wouldn't do it. Even if the circumference is the same now the different tire might wear at a different rate than the other three. Also, considering Subaru recommends different air pressures from front to back it might also be that different sidewall flex from one brand to another might cause problems for the AWD system as well. It is possible that you might get away with it and have no issues at all but I'm not sure I would be willing to risk it.
 

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Discussion Starter #7
Thanks all, great feedback. I will measure the circumference and even do the rotation test.
For now, I have it on the car. If it is not a match, I just need a few weeks to get new ones or the others
put back on.
 

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2002 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
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Thanks all, great feedback. I will measure the circumference and even do the rotation test.
For now, I have it on the car. If it is not a match, I just need a few weeks to get new ones or the others
put back on.
the safest thing you can do,

buy 4 new matching tires,

sell the remaining 3 to 2wd people. (at a consignment / thrift shop, your local friendly garage, on craigslist).

what subaru do you have exactly (year, model, engine, trans, trim)?
= some old plain jane automatics may have a front wheel drive fuse to insert or pull to make it a front drive car so as to prevent torque bind from running mismatched tires.
 

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Discussion Starter #11
So, I measured my 3 matching tires: 91.125", 89.250", 89.250" making the avg.; 89.87.
The newly purchased one is; 88.75" so I am off by 1.12"
According to the good information received here (.25" make difference) I am s - - -wed.
Even though there is still lots of snow forecasted up here, I am forced to put the all seasons back on.
Ugh....
Thank you for all the information.
DD
 

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OBW H6 VDC, Tribeca, XT6
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So, I measured my 3 matching tires: 91.125", 89.250", 89.250" making the avg.; 89.87.
The newly purchased one is; 88.75" so I am off by 1.12"
According to the good information received here (.25" make difference) I am s - - -wed.
Even though there is still lots of snow forecasted up here, I am forced to put the all seasons back on.
Ugh....
Thank you for all the information.
DD
overinflate it, put it on the rear, the VTD can handle it, and rotate the other three into the position that wears the fast (often the fronts depending on driving) and the leave the smaller one on the rear.

nah - just get the right tire. tire price against vehicle and standard maintenance...annoying but not a big deal in the end.
 

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On the Super Mod Squad
2002 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
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can't put a 2012 subaru into Front Wheel Drive mode. (too new).


however, I just thought of a new option,

buy a 2wd that takes the same sized tire as the subaru .
so in the case of a legacy or a outback something like a chevy impala type thing.

so you can swap tires between a AWD and a Front WD car.:nerd:
 

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06 OBW 2.5, 05 Forester, had 03 H6 OBW
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So, I measured my 3 matching tires: 91.125", 89.250", 89.250" making the avg.; 89.87.
The newly purchased one is; 88.75" so I am off by 1.12"
According to the good information received here (.25" make difference) I am s - - -wed.
Even though there is still lots of snow forecasted up here, I am forced to put the all seasons back on.
Ugh....
Thank you for all the information.
DD
You were really far off before this issue! (if you were running the 91.125 with the 89.250's)
 

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'14 Subi OBW, '18 Subi Forester
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Agree that you should fix the tire situation ASAP. But what if you could not.... What would you do?

It's odd that one of your three original matching tires is nearly 2 inches greater in circumference compared to the other two that are exactly matched! Did you measure these off the car, or on the car? Is there a big difference in tread depth also? Something isn't right here.... My bet is that the 91.125 was alone up front, and the two 89.25 were on the rear, and that you attempted to measure them loaded. I don't believe that this was the intent of the 1/4" circumference spec. I think that this is an unloaded even inflation bench test.

With the Subaru, the number one (?) wear concern is front to back balance. So what if you were to do the following? Audience feedback??

With the tires off the car and inflated to the same psi, I'll assume that the 91.125 comes down to around 90.0. Match that up with the new 88.75 tire, and you get an average of 89.375. That would work well with the twin 89.25 tires. No strain on the center duty clutch. Now the question is which axle to put the side to side mismatch. Open differentials probably won't care too much. On an older Subie with a Rear LSD I'd keep those tires the same. On a 2012? The rear differential can probably handle this better than the front case differential given that the care is biased towards FWD much of the time?? Hard to say.....

Like I said, 'audience participation event'!
 
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