Whats the max tire depth variance allowed?

I have one tire that had a big chunk of the sidewall get ripped off on a nasty pothole. Sucks.

Anyways I have one other tire that got a smaller slit in the sidewall but not an issue besides cosmetically.

That was used for about 5k miles while the one with the nasty chunk missing has about 10k on it. There is a slight difference in tread depth however.

So I am wondering what the max safe variance can be if anyone is familiar.

If too much I will have to buy another tire and find somewhere that shaves them rather than buying 4 new tires.

I get bad highway speed vibrations for the chunk out.

I'd imagine I could have the wheel rebalanced but I'd prefer to not have this tire on my car much more. Pretty deep chunk out of it.

Tirerack.com claims:

"Subaru: Within 1/4-inch of tire circumference or about 2/32-inch of each other in remaining tread depth."

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=18

I didn't know tirerack shaved tires, just learned something new myself.

http://blog.tirerack.com/blog/docs-advice-on-tires/needing-to-replace-just-one-tire-on-your-subaru-youll-need-a-shave-as-well

Tirerack.com claims:

 

"Subaru: Within 1/4-inch of tire circumference or about 2/32-inch of each other in remaining tread depth."

 

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=18

 

I didn't know tirerack shaved tires, just learned something new myself.

http://blog.tirerack.com/blog/docs-advice-on-tires/needing-to-replace-just-one-tire-on-your-subaru-youll-need-a-shave-as-well

not only do they shave them, they will heat cycle them, too. So you can run them hard right out of the box. Otherwise, you'd have to put a couple easy laps on them, and then let them cure for 24-48 hours.