The driver rear has a nail right on the side of the tire and needs to be replaced. The guy at the tire shop mentioned that some AWD vehicles need to have all four changed. Would I be able to get away with buying just one new tire? The new tire depth is 10/32. Would there be an acceptable tread depth for the 3 remaining tires that wouldn't affect any operations with the AWD? I read concerns from other people about that somewhere else. The only thing I've found so far in the manual is this comment "Major dissimilar tire sizes between the front and rear axles could cause the AWD system to stop functioning and default to front wheel drive or damage the AWD system". What is "Major dissimilar tire sizes?

 

Tires with minimal tread, such as one with 2/32nd's, is the minimum required by law. A new tire has up to 14/32'nd's in tread, I believe. So, big differences in tread can exist. I wouldn't go more than a 4/32's in difference. This is one reason frequency in rotation is recommended - to prevent major differences in wear. Depending on tread in other three tires, you may be in a pickle since cars come with a spare but often a different size now. Maybe you can get by replacing only two tires at most and then gain an extra spare if need be? Hope this helps.

 

I talked with the tech from the Ford dealership I bought the car from and told him my situation. I had 5/32 depth on the remaining three tires and the new tire comes with 10/32. He said it was fine to put one new tire on the car and I won't have a problem. I did put the spare tire on to drive the car over there to the tire shop and it felt different driving it. Then the message came on that said AWD OFF. It cleared when the other tire was put on.

 

Glad things worked out.

 

Some places like tirerack.com will shave a tire to match the other tires.