FusionDiffusion Posted August 22, 2011 Share Posted August 22, 2011 Just wondering if anyone knows if the rear disk brakes are automatically adjusted for wear, and how this is accomplished? I know the front are self-adjusting, but do the rear require parking brake actuation or driving in reverse? If you have a service manual or know how the mechanism works please enlighten us! Thanks! Extra info: I did a moderately-hard stop from 70 mph and immediately measured rotor temps. The front rotors were about 350ºF and the rear were about 260ºF. Remarkably, temps only varied about 5ºF from left to right! Perhaps this is the work of the electronic brake force distribution system. I know the front brakes will always be hotter, but I would like to see a smaller temperature differential between the front and rear. 0 Quote Link to comment Share on other sites More sharing options...
FusionDiffusion Posted August 28, 2011 Author Share Posted August 28, 2011 Bump — Any brake experts out there? 0 Quote Link to comment Share on other sites More sharing options...
twiggy144 Posted August 28, 2011 Share Posted August 28, 2011 Bump — Any brake experts out there? I am no expert, only passionate about mechanic. Here is my 2 cents. Rear disc brakes self adjust everytime the parking brake cable is applied. The parking cable force is transmitted to a cam inside the caliper piston, pressing the piston against the pads. In addition to that effect, there is a ratcheting mechanism inside the piston, which will pick up and reduce any excess piston travel movement when the parking brake is pulled and the piston is pressed against the pads. This is why when you change the rear pads, the piston cannot be simply pushed inside the caliper to make room for the new thicker pads, like this has to be done with the front calipers, but the rear pistons have to be turned (clockwise) to retract them inside the caliper, with the help of a special piston tool, or with needle nose pliers, like many other amateurs have done, including myself. The rear piston have notches on its edge to allow using the piston tool, or needle nose pliers. 0 Quote Link to comment Share on other sites More sharing options...
FusionDiffusion Posted August 28, 2011 Author Share Posted August 28, 2011 Thanks. I yanked on the parking brake a few times and things have seemed to tighten up. It almost feels like the rear brakes are grabbing before the front ones now (the rear is sinking down a little under very light braking) I guess the lesson is that you still need to use your parking brake occasionally, even if you have an automatic and only park on perfectly flat surfaces. I wish Ford mentioned something about this in the manual because I can't imagine how many people are driving around with unadjusted rear brakes. Maybe this helps explain why I see so many cars that can't obey stop signs and red lights... Yet another reason why manual transmissions would enhance safety for everyone. 0 Quote Link to comment Share on other sites More sharing options...
akirby Posted August 28, 2011 Share Posted August 28, 2011 I wish Ford mentioned something about this in the manual because I can't imagine how many people are driving around with unadjusted rear brakes. You mean like the three highlighted Warnings with huge exclamation points? WARNING: Always set the parking brake fully and make sure the gearshift is latched in P (Park). Switch the ignition off and remove the key whenever you leave your vehicle. Maybe more people should read their owner's manuals more carefully. 0 Quote Link to comment Share on other sites More sharing options...
FusionDiffusion Posted August 29, 2011 Author Share Posted August 29, 2011 You mean like the three highlighted Warnings with huge exclamation points? I was aware of the warnings in the book to the effect of "always apply the parking brake when you shut off your car" as you've dutifully pointed out, but I was thinking they should be more specific add something more along the lines of "Caution: Failure to use the parking brake on a regular basis may cause reduced rear braking effectiveness." Ford has covered it's legal bases with the existing warnings, but adding a little more info might be in the customers' best interests. Even though it says to, hardy anyone with an automatic uses their parking brake every time because they think it doesn't hurt anything. If people knew the lack of use would affect their brakes (and possibly damage the park pawl), I think it would get used more often. 0 Quote Link to comment Share on other sites More sharing options...
twiggy144 Posted August 29, 2011 Share Posted August 29, 2011 In the rust belt where I live, we learn soon to use the cable brake often ( I do daily) , else it will seize in the rust and become inoperative. 0 Quote Link to comment Share on other sites More sharing options...
akirby Posted August 29, 2011 Share Posted August 29, 2011 I was aware of the warnings in the book to the effect of "always apply the parking brake when you shut off your car" as you've dutifully pointed out, but I was thinking they should be more specific add something more along the lines of "Caution: Failure to use the parking brake on a regular basis may cause reduced rear braking effectiveness." Ford has covered it's legal bases with the existing warnings, but adding a little more info might be in the customers' best interests. Even though it says to, hardy anyone with an automatic uses their parking brake every time because they think it doesn't hurt anything. If people knew the lack of use would affect their brakes (and possibly damage the park pawl), I think it would get used more often. Ok, I'll buy that. 0 Quote Link to comment Share on other sites More sharing options...
Snelgrovereefer Posted October 4, 2011 Share Posted October 4, 2011 I am no expert, only passionate about mechanic. Here is my 2 cents. Rear disc brakes self adjust everytime the parking brake cable is applied. The parking cable force is transmitted to a cam inside the caliper piston, pressing the piston against the pads. In addition to that effect, there is a ratcheting mechanism inside the piston, which will pick up and reduce any excess piston travel movement when the parking brake is pulled and the piston is pressed against the pads. This is why when you change the rear pads, the piston cannot be simply pushed inside the caliper to make room for the new thicker pads, like this has to be done with the front calipers, but the rear pistons have to be turned (clockwise) to retract them inside the caliper, with the help of a special piston tool, or with needle nose pliers, like many other amateurs have done, including myself. The rear piston have notches on its edge to allow using the piston tool, or needle nose pliers. WOW, I wish I had read this before last weekend when I changed my pads and rotors on all four wheels; I wondered why it has so hard to compress the rear pistons but did manage to get it done. I have always done my owne brakes and have never ran into a problem. Now however the driver side rear seems a little to tight and the passenger side rear does not seem to be working at all since the rotor has not been scored at all. Also, they emergency brake does not seem to engage well (it would not stop the car if it was moving). What can I do now besides the obvious; taking it into a garage? 0 Quote Link to comment Share on other sites More sharing options...
drolds1 Posted October 5, 2011 Share Posted October 5, 2011 WOW, I wish I had read this before last weekend when I changed my pads and rotors on all four wheels; I wondered why it has so hard to compress the rear pistons but did manage to get it done. I have always done my owne brakes and have never ran into a problem. Now however the driver side rear seems a little to tight and the passenger side rear does not seem to be working at all since the rotor has not been scored at all. Also, they emergency brake does not seem to engage well (it would not stop the car if it was moving). What can I do now besides the obvious; taking it into a garage? There's nothing wrong with your handbrake because it's not an emergency brake. It's a parking brake. See your owners guide. It wasn't designed to stop the car. How did you manage to retract the rear pistons without rotating them in? 0 Quote Link to comment Share on other sites More sharing options...
FusionDiffusion Posted October 5, 2011 Author Share Posted October 5, 2011 On the rear brakes, you have to rotate the piston back in (like a screw) with a special tool. If you just pushed them in with a clamp like the fronts, you might have damaged the piston seals or caliper. After the pads are properly installed, you can give the hand brake a few pulls to tighten up the pads. Also, just because a rotor isn't scored doesn't mean the brakes aren't woking on that wheel. Several of my rotors are not scored. The way you test is to stop the car from 60 mph at a moderate rate, then get out and measure the brake temps (with an IR thermometer or feel the heat with the back of your finger--don't touch the rotors though!). Temps should be almost identical left to right and the fronts will be a little hotter than the rears. For example, front = 350ºF and rear = 250ºF with a 10º variance between left and right in the case of my car. Either way, if the rear brakes aren't working, you or a mechanic needs to inspect the rear calipers and piston assembly. 0 Quote Link to comment Share on other sites More sharing options...
Snelgrovereefer Posted October 6, 2011 Share Posted October 6, 2011 So I just picked up two new rear calipers with all hardware and new mounting brackets. Wow, do you ever have to look around to get the best price and product. First I called Ford and was quoted $300 each, then checked all of the usual aftermarket guys. I was just looking for OEM replacement not a Brembo upgrade or anything and the prices were all over the map. All of the prices are with the core refund already taken off, semi-loaded, all hardware and is each; $221, $177, $136 and $196. I ended picking them up for $119 each from the same firmm that quoted me $136 but from a different dealer location! The best part is that the calipers are reman. FoMoCo's and they have been pre-coated with an nice looking blackish chemical to stop rust and corrosion. Will be replacing them tomorrow night, the only part that I am not looking forward to is bleeding the brakes. I will let you know how it goes. Mark 0 Quote Link to comment Share on other sites More sharing options...
FusionDiffusion Posted October 7, 2011 Author Share Posted October 7, 2011 One more tip here before you dive in: Limit the pedal travel when you bleed the brakes. Put a block or something behind it so that it doesn't go much further than it normally goes with a closed system. When you're bleeding, the pedal will go until it hits the mechanical stops in the master cylinder. Since this is further than it normally goes, the master cylinder pistons sweep an area that they normally don't encounter. If there's any kind of contamination or rust in there, you will tear up the seals and you will have an internally leaking master cylinder to replace. Also, make sure you don't let the master cylinder run dry during bleeding. Otherwise you will have to take it in and have the ABS module purged at a dealer. Use a silicon-based lubricant on the caliper slides and mating surfaces. Do not use regular grease anywhere on the brakes. 0 Quote Link to comment Share on other sites More sharing options...
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