Calipers moving the wrong way? Brakes binding

[jonathanW27]

What I thought was a simple job has turned into a mystery. All I wanted to do was to change shoes and discs on a daihatsu charade.

But on replacing them the brakes are binding on both sides. Spent two days checking everything and it seems to be the caliper pins pulling the Caliper toward the car which means the new pads are binding to the new disc. Any idea what I am doing wrong.

I can see the rubber Caliper pin is sealing air the Caliper hole creating air pressure and forcing the pin out. The other pin has no rubber pin and seems to be ok. Any ideas much appreciated I am stumped.

[Black Lotus]

Just some thoughts--
If it's a single piston caliper, the brake is applied in this order--
The piston moves from the caliper body outboard until it contacts the disc. The caliper continues inboard on slider pins (or bars) until the the ouboard portion of the caliper, which holds the outboard pad, moves the pad into contact with the disc.
Usually what fails is the piston jams in the inboard part of the caliper--which everthing up. Or, the inboard part of the caliper jams on the slider pins-- which locks the outer pad onto the disc.
If it's a rear caliper the piston usually needs to be screwed in to reset the parking brake.
If there is difficulty in pushing the caliper piston in, the caliper bore may be filled with gunk and corrosion. Also, remember that if you are pushing the piston in, the fluid has to go somewhere, which is to go back to the master cylinder reservoir- so you may have to mop up some fluid there.

[jonathanW27]

thanks for reply it is the front caliper and is a single caliper. Whats odd is the caliper pin with rubber end is pulling the outer pad onto the disc tight onto it so it wont easily move the wheel when no braking is applied, the air pressure created in the socket effectively wanting the pin to want to move inbound The piston does not seem seized and i used a clamp and old brake pad to push it back back.

[shorod]

I just ran in to this on a Subaru Outback on the rear. The lower slide pin has a rubber seal, almost like a 1/4" wide o-ring, that slides in the bore of the caliper mounting bracket. With the rubber seal installed, I'm not able to get the pin to bottom out because trapped air wants to force it out. If I remove the seal, the pin slides all the way in with no problem.

I'm not sure what the real purpose of the rubber piece is, I suspect it's to dampen noise. In this case I was able to get the caliper and new pads installed, but you now have me wondering if I need to check the wear of the rear pads in a few thousand miles. The owner said the brakes now work great....

I'm sorry I don't have a solution for you, other than to consider leaving the rubber end out (if that's possible in your application) or use a wire brush in the bore to make sure there isn't some groove that is plugged up with old grease or similar and preventing the trapped air from escaping. FWIW, I used a cylindrical steel brush down the bore of the Subaru to no avail.

-Rod

[jonathanW27]

thanks Rod i ll give it a go tonight and let you know
jon

[jonathanW27]

Hi
Tonight I think I worked it out and it's the amount of grease you put on the slide. The rubber sleeve has tiny grooves to allow the air to pass so pushes the pin out so too much grease and the air cannot escape however too little and the rubber skeeve will seize and the Caliper pin does not move. Also I have to use a special grease called red rubber grease. I need to get the grease tomorrow
Thanks guys for your input see what happens

[shorod]

Please let me know what you end up with for grease. I suspect I might want to redo my co-worker's slide pins.

-Rod

[jonathanW27]

will do if you go on line there is a youtube video about caliper lubrication. Any grease cannot be petrolium based product as it rots the rubber seals/gaiters and cannot take the temperatures. Also dont use copper grease it will seize the caliper

[shorod]

I used synthetic brake grease (the black stuff) that is PAO-based which I understand to be non-petroleum base. The manufacturer website claims it's safe on plastic and rubber parts. Maybe I'm okay with the grease and just used too much, or it's too thick for the channels in the rubber. On the Subaru there were three channels which I felt should have allowed trapped air to escape.

-Rod