hi guys, as far as i understand there are 2 different type of na rear calipers for the 88 rx7... one is numbered 13 15 and the other has the numbers 15 15 on it. i was wondering do these numbers actually make a difference? or can either caliper be used without modification? thanks in advance.

 

Vented rotors vs. non-vented rotors.

If the car is a 4 piston car, then the rear rotors will be vented and you need to order the correct caliper.

Single piston cars had non-vented rotors.

Also, the part numbers are different left to right.

 

Is there a difference between 87 gtu calipers and t2 calipers?

 

No such thing as an '87 GTU; the GTU came out in the '88 model year. Unfortunately the standard specs thread with dealer brochures is missing one of the '88 pages, but I believe the GTU had 4-pot front brakes and vented rears. TII, GXL and convertibles all had these same calipers/rotors.