Rear brakes always this hard?

[yardbirdsax]

Today I replaced my rear brake pads for the first time since getting the car. On the driver's side, everything came apart okay, but the caliper piston was a BEAST to get to compress. Yes, I got the special tool from AutoZone with the notches, and it fit, but I had to put a wrench on the end just to get enough leverage to get it to spin. Yes, I opened the reservoir cap so the pressure wasn't building up (I ended up cracking the bleeder value a hair to see if that helped; it did not, and now I have to bleed my brakes too, argh). With the wheel back on I didn't feel / hear any obvious signs of dragging, but I'll have to check more thoroughly once I have gotten the brakes bled etc. I haven't gotten to the passenger side, thanks to how long this took; hopefully it is not as hard.

So far as I know, the brakes worked fine prior to this. The old pads did not look particularly lopsided in terms of wear or whatnot. The car has 48,000 miles on it, so not high mileage. Some forum searches show signs of intelligence that this (sticky driver rear caliper piston) is a thing for these cars. Anyone here have experience with this? Maybe this is just a sign that I should bite the bullet and replace the caliper? They seemed in pretty good shape (not overly rusty etc), but given these are brakes I don't mind being safety conscious.

 

[Autokyrios]

Did you have the parking brake on? Was the piston turning as it compressed?

 

[yardbirdsax]

The parking brake was not on, and yes, I did use the correct tool to rotate it as I compressed it.

The passenger side wasn't nearly as hard. Combine this with the fact that the driver side pads were more worn than the passenger side ones, and the rotor was noticeably hotter after the bedding drive, and I'm pretty sure I need to replace the caliper. Probably was an existing condition and I only noticed it because I examined things.

 

[JC SSP]

the fact that the driver side pads were more worn than the passenger side ones, and the rotor was noticeably hotter after the bedding drive...

You have a sticky caliper.. Time for replacement.

 

[Autokyrios]

Yeah, time for a new one. Not worth rebuilding, just get a reman and don't worry about it.

https://www.partsgeek.com/catalog/2007/ford/mustang/brake/brake_caliper.html

 

[yardbirdsax]

Thanks! I was planning on replacing the calipers and rotors with the Z23 kit from PowerStop at some point anyway. Guess that time is now!

 

[Autokyrios]

Slotted or plain. Don't like drilled.

 

[DieHarder]

Thanks! I was planning on replacing the calipers and rotors with the Z23 kit from PowerStop at some point anyway. Guess that time is now!

If you're interested you can upgrade to 4-pot 2008 or later GT500 Brembo's inexpensively (front only). I think I spent $400 for everything (some years back). You can order them from most any autoparts store. They look good and work much better compared to stock.

 

[Miker]

Are the rotors from the GT used with the GT500 calipers?

 

[Autokyrios]

I believe the backs are but the fronts are larger.
If you do want to go the route of shifting to another brake setup, you can find complete kits for cheap if you don't mind used or going remanufactured. The master cylinder and ABS module are the same. You may need to grab a GT500 brake booster if things are mushy afterwards (or just do it, they're cheap). Grab some braided lines and a brake job kit (pins, banjo washers, etc) and do it up. Fun and relatively simple project.

I ran remanufactured GT500 front brakes for about a year as a stopgap while waiting for my Wilwoods. Don't have much to say about it other than they worked. I'd offer them up but I sold the calipers and melted down the rotors.

 

[TexasBlownV8]

Are the rotors from the GT used with the GT500 calipers?

Not on the fronts. I too did the front GT500 brake conversion, upgraded rotors and to braided hoses/lines. Pretty easy conversion. You rims have to clear, though, and that can be a problem.
Back rotors are the same on both.

Back to the issue, it does sound like a sticking/stuck caliper. Should have retracted as easy as passenger side did.

 

[Windy_3V]

Seems like the piston in your driver side caliper is starting to seize. Had the same issue with mine. Better to just replace the whole thing than go through the headache of rebuilding it. While you’re at it, I recommend upgrading to some stainless steel brake lines if you haven’t already

 

[GriffX]

You may need to grab a GT500 brake booster if things are mushy afterwards (or just do it, they're cheap). Grab some braided lines and a brake job kit (pins, banjo washers, etc) and do it up. Fun and relatively simple project.

GT500 brake boosters are cheap and fit to the GT?

 

[Autokyrios]

Yep.
LMR has a good price but you can get them anywhere of course (also cardone and such from other places like auto stores and RockAuto, Partsgeek, etc). Just make sure it's specifically for a GT500 model and not the GT one.

https://lmr.com/item/LRS-2005AB/Mustang-GT500-Power-Brake-Booster-07-13

Fit with no modifications. Use the vacuum bleeder that it comes with but just attach the factory GT hose. Hardware on the pedal side is the same.
I put one in when I fit my Wilwood's as the stock GT one is a little underpowered.

 

[ShelbySteve]

I’ve read most people get increased pedal travel with the 6 pot brembos over the 4 pots. I didn’t have that experience and just installed goodridge lines and flushed the old brake fluid with the same pedal feel running 6 pots.

 

[GriffX]

I’ve read most people get increased pedal travel with the 6 pot brembos over the 4 pots. I didn’t have that experience and just installed goodridge lines and flushed the old brake fluid with the same pedal feel running 6 pots.

These brake stuff isn't easy to understand, e.g. larger brake rotor -> less pedal travel, larger caliper piston surface -> more pedal travel

 

[ShelbySteve]

These brake stuff isn't easy to understand, e.g. larger brake rotor -> less pedal travel, larger caliper piston surface -> more pedal travel

My pedal is identical to my 2 piston oem setup with 6 pot s550 brembos

 

[MasterofDisaster]

I had the same sticky caliper problem about four years ago when I changed rotors and pads at 110k miles. I don't remember whether it was left or right, but one took extraordinary force to wind the piston back into the caliper. I cleaned everything up, and they work fine now 35k more miles down the road.

The rear pads were worn much more than the front. I have heard that the parking brake adjusts the rear brakes. I now use the parking brake three days a week in ordinary circumstance. Seems to work fine.

 

[yardbirdsax]

While you’re at it, I recommend upgrading to some stainless steel brake lines if you haven’t already

Ah shoot, that's a good point. I just checked and the auto stores close to me don't stock even the OEM brake lines, so it'd be a couple days. I'm inclined to replace the calipers now, then do the lines later. I'd have to bleed the brakes again, which is , but I also really don't want to drive the car with the sticking caliper more. The other day I measured the rotor temperature after a 25 minute drive, and it was 240 F (I could smell it and feel the heat too).

(Weirdly enough, after driving the next day, they were normal. I'm sure it's an intermittent thing.)

 

[Autokyrios]

Ah shoot, that's a good point. I just checked and the auto stores close to me don't stock even the OEM brake lines, so it'd be a couple days. I'm inclined to replace the calipers now, then do the lines later. I'd have to bleed the brakes again, which is , but I also really don't want to drive the car with the sticking caliper more. The other day I measured the rotor temperature after a 25 minute drive, and it was 240 F (I could smell it and feel the heat too).

(Weirdly enough, after driving the next day, they were normal. I'm sure it's an intermittent thing.)

It's easy to do. Just make sure you re-bleed all your brakes afterwards as you'll have air in the lines no matter how careful you are.

FP (formerly FRPP) used to sell braided brake lines, but I doubt they do anymore. But plenty of places have them. Try CJPonyParts, LateModelRestoration, Steeda or I guess AmericanMuscle.

The lines should all be the same regardless (GT/GT500). It's not really until you get to more serious aftermarket brakes that you might run into differences (e.g. my Wilwoods needed a different connection for the calipers than stock, so I had to use their lines).