The Mustang Forum for Track & Racing Enthusiasts

Taking your Mustang to an open track/HPDE event for the first time? Do you race competitively? This forum is for you! Log in to remove most ads.

  • Welcome to the Ford Mustang forum built for owners of the Mustang GT350, BOSS 302, GT500, and all other S550, S197, SN95, Fox Body and older Mustangs set up for open track days, road racing, and/or autocross. Join our forum, interact with others, share your build, and help us strengthen this community!

Taper in race pads in fixed/6pot brembo calipers

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

captdistraction

GrumpyRacer
1,954
1,698
Phoenix, Az
I was going through troubleshooting the pedal setup on my car (the early S197/Kohr hydraulics make a real long and somewhat overboosted pedal throw with the S550 calipers)

That all said, I thought Id change my pads to new ones to see if that helped pull the brake engagement up. What I found was that both sides had taper. One side in the range of what I'd call mostly normal (less than 1mm from front to rear). However the passenger caliper was 2mm front to rear (and rear to front on the opposing pad).

I ran the new pads and all is well there, however I'm curious what I can do to mitigate future tapering of the pads:

I did remove some shims I was using to center the caliper, but have some other suggestions I need to follow up on:

-My two piece rotors aren't configured to be fully floating. I can change some of the hardware to make them fully floating (which should also help with any perceived knockback)

-slightly sand/grind down the sides of the pads to open up the tolerance in the caliper and prevent binding

-tear down the caliper and inspect the pistons

The seals in the calipers seem to be good, and the dust boots aren't melted. Temperatures haven't been extreme on the caliper bodies and outside the hydraulic setup not resulting in ideal pedal throws, I've not had other issues with the setup.

739b471fd2d811827c1bfc19c7316aff.jpg
 
108
33
Long pedal/overboosted sounds like you have too much piston volume in your new calipers. That could also mean your brake bias has changed for the worse.

Bias aside, You either need a larger master cylinder to better match the increased volume of your calipers, or pick a caliper that has a properly sized pistons for your brake system.

Is it a new caliper? If not you may have a sticking piston. 2pc rotors help a little.
 

captdistraction

GrumpyRacer
1,954
1,698
Phoenix, Az
unfortunately there's no master cylinders I can change (05-09 all had the same size piston internally from my understanding). I'd love to investigate retrofitting the the proper S550 master/booster but I imagine that takes a lot of fabrication.

That said, calipers have about a year on them, they were new.
 
898
544
The respective brembo caliper piston specifications are:

Piston Diameters (mm)
05-14 GT: 44, 40
07-12 GT500: 44, 40
13-14 GT500: 38, 34, 30
2015 GT PP: 36, 36, 36

Piston Diameters (inches)
05-14 GT: 1.73, 1.57
07-12 GT500: 1.73, 1.57
13-14 GT500: 1.50, 1.34, 1.18
2015 GT PP: 1.34, 1.34, 1.34

Piston Area (one side of caliper)
05-14 GT: 4.30 in^2
07-12 GT500: 4.30 in^2
13-14 GT500: 4.26 in^2
2015 GT PP: 4.73 in^2

The increased piston area of an S550 caliper will result in longer pedal travel, but the system will generate more clamping force if you do not run out of pedal travel (i.e. pedal contacts floor).

But, you also changed your master cylinder. If the new master cylinder has a smaller piston than the one it replaced, this will also result in a longer pedal.

Find out what the piston size of your current master cylinder and the size of the original unit. I suspect you might have installed a smaller master cylinder while at the same time moving to a front caliper with greater piston area and volume.
 
I think it’s more caliper specific than the master cylinder. If it was the master cylinder wouldn’t all the pads wear consistently, in theory at least? What I mean is if they were wearing in a tapered fashion due to the master cylinder they would all wear in a tapered fashion and not just one set of pads.
 
898
544
Yes, I apologize for derailing this thread. My reply was specific to pedal travel and has nothing to do with the original taper issue.

I would check the wheel bearing like JAJ mentioned. It wouldn't take a lot of play to cause the taper issue. Also, puts some lug nuts on the hub, tighten them down, and see if you can check how squarely the caliper is mounted in relationship to the rotor. When you shimmed the caliper it might have become slightly misaligned with the rotor.
 
Last edited:

TMO Supporting Vendors

Top