Compressing caliper pistons

Hoping someone can help. My wonderful VA state inspection a few weeks ago didn't uncover my rear brakes were worn. Yesterday I was metal to metal. I decided to try and tackle this on my own. Bought the pads and rotors and started getting busy. I didn't compress the piston far enough before I took it apart and now I'm stuck. I have enough room for both pads, but not enough to fit over the rotor. I can't seem to get the piston to compress any more. Anyone have any suggestions? I guess draining the brake fluid will reduce the pressure? I'm trying to avoid bleeding the brakes, but I guess it wouldn't hurt to replace the fluid too since I'm learning new things here and seeing I've only had "Jack" a month or so, who knows when it was done.

A c-clamp is usually the easiest option if you have one. If you don't have a flat piece of metal like shown in the picture, a wrench laid across the brake piston will work too.

http://www.4x4xplor.com/images/disc-brakes/DSC09428.jpg

Make sure the cap is off the master cylinder.

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Originally Posted by Triathlete

Make sure the cap is off the master cylinder.

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Also make sure you don't push any fluid out of the master cylinder and spill paint eating brake fluid everwhere

Thanks all. I ended up getting a kit from O'Reilly to compress the piston...and called a male friend over to use his strength. We got er dun. Both sides completed with rotors in under 30 minutes.

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Originally Posted by Y33TREKker

A c-clamp is usually the easiest option if you have one. If you don't have a flat piece of metal like shown in the picture, a wrench laid across the brake piston will work too.

http://www.4x4xplor.com/images/disc-brakes/DSC09428.jpg

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I use that method but instead of the flat plate, I use a deep socket to push against the piston (of course, it's a little more tricky to do it whilst the caliper is still attached to the vehicle by the brake line). I like my old vice-grip caliper compressor but can seldom get it at the right angle with newer calipers.

I've always just seated the C-clamps screw anvil against the bottom of the piston and compressed it that way. It takes a little more turning but I'm not balancing spacers or plates against the piston.

Sorry to be on topic, but it's a good idea to open the bleeder screw when compressing the piston, so any debris in the brake fluid at the piston is bled out rather than just being forced back up the line.

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Originally Posted by BigSwede

Sorry to be on topic, but it's a good idea to open the bleeder screw when compressing the piston, so any debris in the brake fluid at the piston is bled out rather than just being forced back up the line.

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How dare you un-jack this thread!!!

Actually I disagree. Unless you have a brake bleeder set up, you're likely to get air in the line when the piston reaches the end of it's compression. I'd rather have debris in the line than air.

It would be a good idea however to clamp the caliper on the opposite side of the vehicle so that as you compress the side you're working on, the piston on the other brake doesn't de-compress to the point of disengaging the guides or damaging a seal. That's why I always complete one side before I start on the other (go ahead ... ask me how I know:)).

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Originally Posted by tom4bren

Actually I disagree. Unless you have a brake bleeder set up, you're likely to get air in the line when the piston reaches the end of it's compression. I'd rather have debris in the line than air.

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Yes, you would certainly want to bleed the brake lines a little to remove any air.

11 Good "on topic posts" and 34 deleted crap posts... C'mon guys, do we have to do this again? Stay on topic or it won't be just coal you get in the VX.info stocking...