Shaving new Tire for subaru AWD

[winnietrey]

Thought I would ask this question in this forum, as from what I read here, you guys seem pretty smart on mechanics.

So here is the story. Wife picked up a large hole in the right rear on our 2015 Suby Forester ( with 15K on the clock). Tire is not reparable. So options are 1)Replace all 4 tires, or 2) Dealer says they will get same tire and shave it down so it matches wear on the other 3. They say all will be peachy.

My understanding is Suby AWD, is extremely sensitive, and if tires don't match as to size (as in tread wear), you will blow the Tranny.

Until yesterday I did not know one could shave a tire. So any thoughts would be greatly appreciated.

Mod If I posted in the wrong place I apologize, please move as you see fit

[Cider]

Went through this scenario myself. Our Forester had a non repairable flat on right rear. Subaru comes stock with Yokohama tires, which I really don't care for. Opted to go ahead and replace with a new set of Michelins. Owners manual even speaks to keeping tires at same tread depth or drivetrain issues arise. One of the flukes about Subarus, also cannot run chains for snow.

[_DJ_1]

I don't mess around with tires, belts or batteries. Every thing gets changed at 5 years. I would head to Les Schwab for a new set of Toyos. If you destroy another tire it won't cost anything with their road hazard guarantee. I've used it twice!! :C

[RinconVTR]

winnietrey wrote:

RinconVTR wrote:
What is Subaru's tolerance for tread depths???!!!???

No one asked this critical question. That's crazy. Know the answer before you opt to do anything but buy one new tire.


Out of Subarus spec?

I do not believe in shaving anything but race tires. So if you're out of spec among tread depths per Subaru, buy 2 new or a new set of 4.

Subaru says 1/4 inch

That is what I've heard as well, but never saw documentation.

If true, the OP needs to know if his old tires are that much smaller than the new ones. I doubt they are. 1/4" is significant ever after 15k miles. But could be close depending on the type of tire and tread wear rating.

And FYI...this is not just a Subaru thing.

[Turtle_n_Peeps]

No problem at all with shaving a tire. I did lots of them when racing. The only problem I had was getting sick when looking at the thousands of miles of rubber I just shaved off piled up on the floor. :E

You have to measure tires. Just because a tire has the same numbers does not mean it's the same size. We use to "grow" tires to get stagger. We could grow a tire an inch or two so it's very important to measure them.

[time2roll]

steve-n-vicki wrote:
What makes you think they are all the same size when new?
Id bet if you measure the tires right now the front ones are smaller than the rears due to them wearing faster

Do you have a Subaru? I find mine does not have the typical fwd wear issues. Very even all around due to the awd spreading the torque.

[BenK]

This is what the three differentials have to deal with




Why running on good traction and in 4x4 lock WILL destroy the transfer case....why they have AWD...AKA...full time

That the computers expect them all to have the same rev's per mile...calculated for each corner

If a tire isn't rev'ing within an expected rev per mile...it is slipping, skidding,etc...so those computers will "do something"

Then, that the three diffs will slip if not LS or locker...locker on the center diff (third member) is 4x4 lock...AWD is the full time and has a slippage mechanism...in this discussion...fluid coupled third member

[winnietrey]

RinconVTR wrote:
What is Subaru's tolerance for tread depths???!!!???

No one asked this critical question. That's crazy. Know the answer before you opt to do anything but buy one new tire.


Out of Subarus spec?

I do not believe in shaving anything but race tires. So if you're out of spec among tread depths per Subaru, buy 2 new or a new set of 4.

Subaru says 1/4 inch , between tires. Buying two does nothing other than blow the diff up. Because on a subys as far as I can tell, it is not a 2 tire thing it is a four tire thing, due to the fact subys, are AWD all the time.

[steve-n-vicki]

What makes you think they are all the same size when new?
Id bet if you measure the tires right now the front ones are smaller than the rears due to them wearing faster

[RinconVTR]

What is Subaru's tolerance for tread depths???!!!???

No one asked this critical question. That's crazy. Know the answer before you opt to do anything but buy one new tire.


Out of Subarus spec?

I do not believe in shaving anything but race tires. So if you're out of spec among tread depths per Subaru, buy 2 new or a new set of 4.

[All_I_could_aff]

There's more difference in tire radius to the ground with one tire 5 psi lower than the other 3 than if one has full tread and the other three have half tread. I'm not saying it is ideal to have one new, but on a 28 inch tire example, half tread might be half inch shorter than new. That's about 2 percent.

[BenK]

Two issues and naturist is spot on in regards to fluid coupled third members...it will get hot enough to burn...but inside gearbox...little fresh air...so it continues to heat up even more

It will spew hit fluid out the vent and will flame As soon as it gets fresh air

Or, it will lose lube properties...to then have the bearings go metal to metal...and fail by seizing...which might crack the gearbox case...to allow fresh air in...to then flame...

Other, is that ABS,Traction control, AWD, etc computers counting revs per mile for EACH wheel....it might see that one outside of the expected rev's for THAT condition...one might set the brakes, ABS buzz one tire, or what other components and/or systems are in that game...

Shaving tires is NOT as easy as it sounds...

The tread profile MUST be kept and there are cams for the shaver head to follow

The tire HAS to be ROUND with in spec for that tire and the other three

A BIG ETC...worked my way through college as a tire monkey...

If me, I'd get FOUR new tires. Ask how much the dealer will pay...most likely no...so sell them on Craigslist/etc

[dangerbird]

Besides the above mentioned mechanical issues, there can also be control issues when different wheel speeds are detected by the speed sensor at each wheel. It can affect anti-lock braking, traction control, and vehicle dynamics control.

Carl

[Mortimer_Brewst]

My experience with OEM tires is that their quality is lacking. I would look at the reviews of the tire on tirerack.com. If the reviews are good I'd go for the shave. Otherwise I'd get 4 new ones.

[Searching_Ut]

Had to buy a new Michelin for the wifes Awd Equinox and have it shaved to match the other three OEM tires at around the 20k mark. They now have approx. 55k on them and look like they have at least another 10 to 15k left. Some OEM tires do much worse. I doubt I'll get 30k out of the OEM tires on my Ram.