Replacing two tires

[arizonaadam]

Originally Posted by crabjoe

When they did the RF balance, did the just stick it on the balancer then come back and say they couldn't be balanced? If so, they need to try again because it still might be able to be balanced.

They should dismount the tire and check the balance on the rim, by itself, because the problem might be the rim itself. Also, some rim/tire combos just need to be remounted in a different position to balance out.

All very true. I'm not in love with the dealer but since I expected them just to tell me they couldn't duplicate I'm happy they're doing anything.

[arizonaadam]

Originally Posted by Nickshu

It's in the owners manual. It's also in the factory service manual, which I can check when I get home and post a screenshot. Your dealer should know better.

This would absolutely rock, please consider it if it's not too much trouble!

[lavarock]

I would go with 4 new tires. You have two bad tires. I suspect you will find all four are from the same batch. Check the date codes. If they are from the same batch you have two more that will most likely go bad then you will have two new shaved tires and will have to shave two more when you replace the ones that were on the car from the start.

[grossgary]

do whatever you want. replace all 4 tires and be done with it, you've already decided.

there are options if you want or replace just two but you've decided and moved on, just get on with it you're good to go!

new car owners tend to be far pickier than what actual, practical experience may dictate, what can and can't be done by experience, what failure modes are out there, causes, folks actually tearing apart transmissions, etc. most folks aren't going to trade in new ownership anecdotes and philosophies and adopt practical, older vehicle ownership routines.

there is truth in both realms but best to stick with yours, which you've already seemingly decided on.

[RobMunach]

Originally Posted by lavarock

I would go with 4 new tires. You have two bad tires. I suspect you will find all four are from the same batch. Check the date codes. If they are from the same batch you have two more that will most likely go bad then you will have two new shaved tires and will have to shave two more when you replace the ones that were on the car from the start.

Just trashed one of my OEM tires at 22k with an un-repairable puncture. Since they were over half done, I decided to bite the bullet and buy four new Michelin Defenders for $620 OTD (after rebate) instead of trying to find a half worn used tire or getting one shaved. Now I have three extra tires in case I wear out some of the Defenders early or trash one of them.
It is amazing how many Conti ProContacts in the Outbacks size that I was able to find on Craigslist. I wonder if the ones that won'f RFB properly get on there? That is why I did not want to buy a used one.

[arizonaadam]

Originally Posted by grossgary

do whatever you want. replace all 4 tires and be done with it, you've already decided.

there are options if you want or replace just two but you've decided and moved on, just get on with it you're good to go!

new car owners tend to be far pickier than what actual, practical experience may dictate, what can and can't be done by experience, what failure modes are out there, causes, folks actually tearing apart transmissions, etc. most folks aren't going to trade in new ownership anecdotes and philosophies and adopt practical, older vehicle ownership routines.

there is truth in both realms but best to stick with yours, which you've already seemingly decided on.

I will not lie, I'm excited about this car going out of warranty! This is my first new car and my nature demands I get all the value out of it I can. I've driven beaters most of my life and only bought new becasue we had babies.

However, I would probably not buy 4 new tires but for the warnings, apparently prudent, about tires of different sizes. This thread has given me a lot of useful responses which have helped considerably. In the end I will indeed "do whatever [I] want." This is sort of an opportuinty to get 4 new tires, which will carry me around for another 3 years at least.

[Green LTD]

Originally Posted by arizonaadam

I'm fairly sure they mean circumference, not diameter.

You may be correct-So I could do the math if I knew the tires were inflated to the proper pressure etc., but sounds like 1/2 inch in circumference is pretty close to the 2/32 number then. Given actual working diameter of installed tires at given pressures the radius from road surface to center of axle can vary quite a bit. Tread depth with a simple depth gauge on the exact same tire from the same manufacturer would be a much simpler calculation. The op and others all are using the standard 2/32 tread depth. Certainly if installing tires of different style or manufacturer the circumference as measured off the car at a standard pressure would be your best bet. In which case I would have taken the gift tires, got what mileage I could from them, and bought good tires then.

[plain OM]

Originally Posted by arizonaadam

Thanks. I see that 2/32 number on Tirerack. Is it anywhere else? Somewhere I can show the dealer?

Originally Posted by Startiger

On the 2/32" number, that is out of the owner's manual. They can't argue with literature directly from Subaru.

Originally Posted by Nickshu

It's in the owners manual. It's also in the factory service manual, . . ..

Originally Posted by Green LTD

. . .sounds like 1/2 inch in circumference is pretty close to the 2/32 number then. . . .

I have never found a Subaru document with a tread depth difference specification related to the AWD system. (We're not talking about the minimum tread depth for safety, that is, the point where a tire should be replaced.) Nor have I see a 1/2-inch circumference specification. If it's in the Owners Manual and/or the FSM, please, please, identify where and post a photo or complete quote.

The only clearly stated requirement I've found is that the rolling circumference of the four tires should be within approximately 1/4-inch of each other. On a 17 inch tire in the size ranges installed on recent Subarus, a 1/4-inch difference in circumference between tires would result from less than a 2/32-inch difference in tread depth.

Measuring tread depth for the purpose of checking for the circumference dimension requirement is only an approximation. If two tires (same brand, model, size, and inflation have tread depths that differ by almost 2/32, there's a pretty good chance they're circumferences will be different by more than 1/4-inch.

As far as something to show the dealer, suggest they look at the related article in the December 2010 issue of Subaru TechTips (it's available from the Subaru STIS website -- dealers should have ready access), which is also shown in: Tire circumference spec confirmed by Subaru (TechTips).

[Saint J VT]

We had the right-front tire that was Bridgestone, blow-out from a piece of rebar concrete reinforcement rod sticking out of a concrete curb at a lousy tight-turn just at a bridge. We had to use the donut spare.

I measured my depth, which was about 2/3 gone and went online and found an identical used tire and had it shipped to me. The tire depth was astoundingly-the same as our existing three tires!

When my mechanic went to install the 'new' used tire, he showed me where two holes had been patched with rubber plugs. I told him to cut them out and repair the tire the way a radial should be patched, from the interior. So, I spent about $32 for the used tire, about $20 to have it shipped to me, then, about $38 for my mechanic to repair two holes, mount & balance the new-used tire.

All that for about $90 total. Looking back on it, I would have been better off just buying four new tires.

As for the aligning kit, there are special shims, cam bolts, etc. to do the rear aligning with the front. I also questioned some similar charge at one point in time, as I recall.

[Green LTD]

If my calculations are close, based on a 27.6" tire, 1/2 inch in circumference difference is equal to 2.5/32 of tread depth. this is 1/64" or .0156" over the always given 2/32". If you are under the 1/2 inch measured circumference you are very close. (Most tape measures are not going to be able to measure it!)