Rear brake caliper - piston will not go back in....

[shieldr]

Hi


Rear braking was ultra[size=78%] poor so bought some pads and took off the caliper. Pads fine but pistons filthy.  Pumped them out a bit to clean with toothbrush and smother in red grease.  Now can't get the stiff side back in.  Haven't tried a G clamp.  Any tips please to get the piston back in?  Am tempted to buy a new caliper.....[/size]    Any good sources for new calipers?  Many thanks.

[Fazerider]

Chances are that if you do succeed in forcing it back in, it won't retract fully in use and the braking performance will drop off pretty quickly afterwards. Better to pop out both pistons, then you can clean them and the caliper properly and replace the seals.

[shieldr]

Thanks. What's the best way to pop the pistons out? I saw a guy on youtube with a workbench using compressed air. Can I use the brake pedal to pop out? Then what happens to the fluid?

[bandit]

You can use the brake pedal to get the pistons out but the fluid will make a right mess,open the bleed nipple with a piece of pipe attached, pump pedal to empty into a jar then tighten bleed nipple, disconnect the brake hose from caliper then use a foot pump with the red adaptor that comes with it into the brake hose hole & pump. You need to hold one side in & force the other side out (don't use your fingers) as they come out with great force, replace one side first then hold them in & force out the other side.     

[Fazerider]

Yes, you can use the brake pedal to push them out. I use a thin G-clamp to stop the one that moves more easily and use the pedal to push the stiffer one out, then wriggle the second one out with my fingers. Obviously there will be brake fluid slopping out of the open cylinders so be prepared. If you jam the pedal down an inch or so it should stop the reservoir emptying.
Unfortunately, bleeding the back brake once you've got everything back together is often a struggle... air bubbles get trapped in the master cylinder as well as the caliper. Loosening the banjo at the top to let them escape usually works for me.

[Dave48]

When you have the pistons out examine the seals as they can become "tired". If in doubt as to condition best to replace-after all you shouldnt need to do them again for a long time.Make sure the grooves that the seals sit in are spotless. Remove any build up of corrosion/dirt etc with a SOFT tool that wont damage the alloy of the caliper. Powerhoue Automotive in Chesterfield do a complete rear brake overhaul kit for about £20. The seals fit unlike some pattern ones!
When replacing pistons make sure they enter bores at right angles-dont use force-they should go in fairly easily if straight. Good luck!

[Rob]

Use a zip tie to hold the ones you don't want in.

[gingernut]

 Yes I had the same on my rear brake , Piston stuck solid , as other have said , bleed , take the calliper off , and pop the pistons out , ( maybe use the back brake pedal and pop the pistons out this way)> Because my piston was stuck solid , i had to get a piston removal tool then , replace seals, mine was so gunked up …..


 ginger x
 

[me_groovy]

you might find that you've passed one of the seals in taking it out, that's then swelled up so much that the pison can't get back past it.
If it was me, I'd consider doing a seal change while I was there.

[shieldr]

Thanks for all the top tips. Went into ride on in Glasgow today to buy; seals, brake fluid, a wee hose and some swarfega. Plan is to retain the free moving cylinder with a spanner and use hydraulics to pop out the stiff one. Get the other out, clean thoroughly then reassemble with new seals. My biggest concern is the seized bleed screws. They have been scooted with wd40. All I need is a bit of time to do the work now. Cheers.

[RMT1983]

Could just fit one of these!!!

Pm me if interested, got a couple ready to go!

[shieldr]

Looks great. Will pm tomorrow. Thanks.

[RMT1983]

Email if you want buddy,

I'm out tomorrow having my bike Ivanised by Mike....................

Richard_Tindall1983@hotmail.com

[shieldr]

Ok. So I should have used a g clamp or zip tie😐. I have ordered a fzs1000 caliper to upgrade. Best way now to split the one in photo? Will need a bench vice if am to split the body of the caliper....hate having the bike off the road.

[His Dudeness]

If you don't have a vice. Lever the piston back in a small bit. Attach it back onto the bike and undo the bolts holding the caliper together. Are the two pistons moving now?

[shieldr]

I can shoogle them a bit. I should be able to get them over the brake disc and do as you suggest thanks. One of them is nearly out. The inner one seemed pretty jammed when I was pumping the brakes that's why I kept going. Cheers.

[His Dudeness]

Personally I'd push the one that's moving back in most of the way and clamp it and then use the brake pedal to push the other one out most of the way, then clamp that one and pump the other one out until they're out evenly, then split the caliper. If you split it with the stuck one still in most of the way you'll struggle to get it out without damaging the piston