New too the mustang world and doing a break and rotor change, I’ve seen 12.4 or 13.2 for the front rotor size.. I have a 2014 gt base automatic.
thanks in advanced

 

13.2. They increased to that on the 2011-2014 because Coyote. The exception would be the Brembo package which are larger still. You don't have that on the base GT, likely.

12.4 is for the 2011-2014 V6, but is also the same for the 2005-2010 Mustang GT. That's why you're hearing the differences.

Hope that helps, and welcome to the forums!

 

13.2 for the stock brakes system. If it were a Brembo car it would have wheels on it like this from the factory and the brake caliper would look that that also. That is the 14 inch brake option.

 

12.4-inch front rotors are for 2005-2014 models, for V6 are 11.5 inches.

 

Front rotors changed in 2011, the GT got bigger 13.2 and the V6 got 12.4.