s4, s5 caliper question
 

isnt the s4 and s5 calipers the same? both are non turbo. Cause i had bought brake pads for both and they was the same product number.

depends on the set up.

For the 4 piston front brakes with vented rear rotors, yes the brakes (calipers/pads/etc) are the same for both series.

But for the single piston front brakes, no the calipers are different between series.

sorry i was talking about the rear. im pretty sure both of them are single piston front. 91 coupe, and a 86 base

no, different calipers however, they might use the same pad.

Solid rear rotors, had either 4 lug or 5 lug

Yeah, your 91 is 5 lug, and the 86 base is 4 lug. The rear pads are the same for all fc's, I'm pretty sure. In fact, they are the same for my wife's '03 Mazda 6, too. I guess mazda liked that pad size for rear calipers.