im going to buy tires today, but i was wondering if anyone could give me some recommendations on what size. im running 15x7.5 rims in the front and 15x8.5 in the rear. i want a tire that is a little meaty. any thoughts?

 

If the backspacing is fine you could run like a 235 wide front or a 245, and rear you could go 255, maybe 265.

 

Mustang Wheel and Tyre Chart

 

Ok, what about side wall? Maybe 55 or 65?

 

I tend to stick with a 25.5-26" diameter tire myself.

 

There are many variables, but what matters most is how much room you have currently on both sides and the top. Then it's a matter of doing some basic math to see what will fit without rubbing, etc.