I'm desperately trying to find some ACCURATE data regarding the 99 spec front brake setup. I've seen various measurements for all dimensions, sizes, rumors and unclear information... and I cant seem to get the few specific numbers that I need. I've seen conflicting reports, but from my best understanding the 99 spec rotors are 314mm (diameter) x 28mm (thick). I am also wanted to discuss the 99 spec caliper's pistons (different pistons for leading and trailing if memory serves).

So the information I'm after is:

1: What are the confirmed stock 99 spec rotor dimensions?

2: What sizes are the 99 spec front caliper PISTONS (and if you have it the stock 93+ piston sizes). I'm wondering if the bores are the same, and if so, if the stock 93 calipers can be rebuilt with 99 parts as the 99's are set up. Also what are the advantages of having the 2 different type pistons on the 99 caliper? do they press on the pad unevenly? I'm not sure I understand the arrangement.


(pic courtesy of damian)

 

I don't have the 99 spec brakes, but have been assuming that FDNewbie's site provides accurate info:

http://www.fdnewbieimports.com/Backu...t3pic.php?n=44

If you average the piston areas on the 99 spec caliper, i think you will find they closely match the area of the 93-95 US 36.1 mm front caliper. Since they are using the same rear caliper, this is how they preserve brake bias.

I believe the caliper diameters are different to control pad taper (more wear tends to occur on the leading edge, so the pistons are designed to apply a little more force on the trailing to compensate). I had always thought that maybe the 93-95 US caliper obtained the same result with that oddly shaped diagonal backing plate that comes with the stock brakes (the one you need to install with the cut-away arrow pointing up).

 

Search and suspension Archives are your friend:
#1 and most of #2 are answered here
https://www.rx7club.com/suspension-wheels-tires-brakes-archive-112/2002-rx-7-spirit-r-brakes-218468/

Staggered piston sizes are generally for the reasons primerGrey stated.

I have a used set of front 99 rotors if anyone need them.

 

really? ive never pulled a set of front pads off and had un-even pad wear though... a low pad is usually has consistent wear leading and trailing (from what ive noticed). thats why im having a hard time wrapping my head around the idea of different brake pressure on different parts of the pad.

 

yeah ramys website lists the 99 rotors as 32mm thick, and a few other sources on the board have said they are 32mm, however, the 99 spec rotor (precision brake co) lists the rotors as 28mm front (and those were actually produced). can anyone clear up this discrepancy?

im not sure i believe they are 32mm thick. anyone got 99 spec rotors and a caliper gauge handy? -Heath

 

the 99 rears rotors are the same width as the regular USDM rotors. Its all there in the thread I linked to.

the larger diameter rotor will exaggerate uneven pad wear compared to the regular USDM front brakes due to the leverage factor of a larger rotor.

 

this site states the front thickness is *20mm* (obviously wrong) http://www.rx7.net.nz/newrx7.htm

The 99 spec rotor GB thread (which i cant seem to find at the moment) states that the fronts are *28mm*

ramy states on his website that they are *32mm* thick http://www.fdnewbieimports.com/Backup/product.php?n=44




... which is the correct measurement?

 

The front 99 spec rotors are 32mm thick..........

The rear 99 spec rotors are 20mm thick............

Both are the same width, over 312mm wide............

 

THANK YOU SO MUCH!!! Exactly what I was looking for! -Heath

 

do upgraded brake kits like brembo etc use unequal piston diameters? i cant say ive seen it before

 

Yes, many do. Some OEM brakes also.


I used to run a 99 BBK fwiw. Now running the Racing Brake BBK.