Lets hypothetically say that the front right tire blows out, do you have to replace both tires? Milage would be about 5-7k on both. Thanks.

 

Fronts are not as critical diameter-wise as the rears. That being said 6-7K difference is quite a bit, I wouldn't really run thrm with more than a 3-4K difference, but your actual wear and mileage may vary
Good Luck!
Mike

 

It would depend on the wear of the tires. If the two tires on the axle have different wear, your handling would suffer. You could get different responsiveness depending which way you turn. If it were to happen, just take the tire to a trusted tire shop and talk to the guys in the shop instead of the salesmen in the showroom who might try to sell the 2nd tire 99% of the time.

 

How worn are the tires? I burned through my set of RE050's in 5k miles.

So hypothetically, say they were at 2/32'nds, when they were originally molded at 9/32'nds (difference is 7/32'nds). Multiply by 2, and you'll find that its .4375 inches different in total diameter. Originally, the tire was 24.8" in diameter (so 5280 / (2.066666 feet * pi) = 813.2 revolutions per mile), and now its 24.3625" (so 5280 / (2.030283 feet * pi) = 827.8 revolutions per mile. So one tire is rotating 1.8% more than the other.

Despite the handling difference, you'll feel the car pull to one side, which will also bone up your overall tire wear characteristics. It'd be akin to running a decent amount of overall toe in on your front axle.

 

Tread life really is not as important as the tread depth. Measure the tread depth at a tire shop. If you are at 7/32" or about you can do one tire no problem. If it is below that I would either have the tire shaved to match or get two tires.
If I can help let me know.

 

Hey now, I'm a salesman at a tire shop....but I have all the technical know-how and skills too. I would say to replace the other tire NOT because I'm a salesman and it's more money for me , but it's a better idea for the car.
You should not have 2/32 or more difference between two tires.
Example: My front tires brand new have 10/32" tread on them. Due to my mileage and driving style, they now have 8/32" tread. If I blew one of them, it would be okay to replace just one. (but I would replace both, because I'm anal and want to have matching tires in every sense of the word.)
If they had less than 8/32" tread and one blew, replace BOTH. Otherwise you may have driveability problems, possible alignment issues, etc.
If you had the same situation happen for the rear, DEFINITELY replace both tires, especially if the vehicle's drive system/differential is sensitive. If you had one tire that read 5/32" and put one new one on (10/32"), it could be pretty hard on the diff. It's possible to suffer damages ranging from wearing the gears faster and the fluid needing to be changed sooner all the way to complete failure/metal shavings/flinging gears out the diff. cover.
We had a Kia Sorento (all-time AWD) come in and get custom rims and two tires. We replaced them with the same model (Michelin Cross-Terrain)...but we put two "S" speed rated on, and all 4 of his stocks were "H" rated. Believe it or not, there was a total of 1 inch circumference difference between the new S's and his existing H's. The reason for replacement was not wear, but he blew one out because he's an idiot and hit a curb.
The new S's were on the front, old H's on the rear. 2 weeks later, we got hit with a bill from the local A-hole Kia dealership for 2K...claiming because of our tires we put on the front differential bearing got fried, and the transmission and transfer case fluid was black and sparkly from fragments of metal shavings. I said , but by then it was too late and we paid for it.

Long story short: If you're anal like me, replace both tires. If there's more than 2/32" difference between a new tire and your existing good tire, replace both tires. If it's on the rear, replace both. Better to be safe than sorry.
Hope that helps!