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Discussion Starter · #1 ·
I'm trying to change the front brake pads on my Bonnie, but can't get the caliper pistons compressed. I've already bled the line dry of fluid and they still won't go down. Any suggestions?
 

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Have you removed the front brake reservoir cap? That helps.

Are you doing the pistons by hand?

Incidentally bleeding the line dry was not necessary, but that's OK, we'll deal with filling the line up in due course.
 

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Discussion Starter · #3 ·
Yes

Yes, I had the reservoir cap off first, and when that didn't work I loosened the bleed screw on the caliper to let some of the pressure off, and when that didn't work I bled it dry, and the pistons are STILL stuck!
 

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Are they straight in the bore? Sometimes it is possible to get the pistons going in at an angle and then they will stick.

Are the pistons sticking out very far?

Try applying a very small amount of pressure with a G clamp, and see if you can free them. If they will not move stop immediately. In that case try pushing the pistons from side to side to free them up.
 

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Were you trying with your hands [or fingers]? I tried that but would not budge so I used channel locks with a piece of wood across the pistons - squeeze!
 

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Discussion Starter · #6 ·
One is out further than the other and I was pushing against the far one using the old brake pad and a C-clamp. I tried turning them, but they wouldn't even do that. I thought at one point that they may be cocked, but they're not. Arrgh!
 

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Sounds like the perfect excuse to buy that beautiful Beringer 4-piston caliper! Oh, and may as well get the EBC floating rotor while you're at it. Of course, you'll have to drain the... no, you've already got that covered :p
 

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No thanks.
Four pistons equals twice the head-ache!
Ah, but so much more accessible and easier to change.

Remove the one pin, jiggle the old pads a little to retract the pistons and slide in the new ones!!

All done in 5 minutes!



Did you get your stuck piston problem solved?
It sounds like they're canted a little and jammed.
Gentle persuasion should do the trick.


V.
 

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Discussion Starter · #10 ·
Those calipers look nice... and expensive. I haven't freed them yet. I'll try again tomorrow. If it doesn't work I'll remove the caliper from the feed and try again and if that fails it's off to my local bike shop! I'll post my progress.
 

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5 minutes to change pads in a beringer caliper. That must be including the smoke break and coffee.
OK.
I admit to a little artistic license!!
But didnt want to labour the point!!

Two minutes including finding the camera to take the photo!!
:)

V.
 

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For the stuck caliper pistons it is a pity that you have drained the fluid. Often to free them up, applying a little pressure by the lever will force the pistons out a little bit, free them up, then you might want to clean the outside of the piston as best you can, then try to push them back in. Most times that I have experienced piston seizure is when the build up of road crud on the piston causes binding. If you can keep them clean, or at least not with crud baked on, then you should be able to press the pistons in with a firm hand.
Cheers, Simmo
 

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Discussion Starter · #16 ·
Wits' End

Still stuck. I took the caliper to my local shop (not a Triumph dealer, but pretty knowledgeable guys) and they had no ideas. I hooked the caliper back up to the system to see if I could push the pistons out with the fluid, but I can't seem to get any real pressure. I am not a mechanic, and don't know what else to do besides running without a front brake for a while?

Everyone has said that the pistons should simply push back in but Thor himself could not move these things! They were working fine when I took the pads out, I'm pretty sure they're not cocked, and they're both stuck although one is sticking further out than the other. The shop guy said to try a heat gun to the caliper to free it up, but I doubt that'd work.
 

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Don't ride with no front brake! :eek:
 

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Presumably when you hooked the caliper back up to the system you replaced the brake fluid, but did you bleed the line? If the line's not properly bled you won't ever get enough pressure to move the pistons - hence the reason it's so important to bleed a brake system. If you don't already have a bleeder, most auto stores sell a little bottle-and-hose arrangement that makes one-man bleeding incredibly easy, or you can buy a speed bleeder (at greater expense) from NewBonneville.com but you still have to hook up a hose and some kind of collector cup, so I recommend the cheapie plastic bleeder kits.

Once the line is bled, put a piece of wood between the pads first so you don't accidentally close it all the way, and gently squeeze the lever to see if you can get the pistons to move at all. If so, clean them like crazy and see if you can't push them back in. If you can't get them to move at all even with a properly-bled brake line squeezing the lever, then you'll probably need to replace the caliper.

And if you do *have to* replace the caliper, for the love of gods, get a better one. The incremental cost when you have to replace anyway would be hard to pass up.
 

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I did have a caliper once that had stuck that bad.

The problem with your brake bleeding is that it takes time to get brake fluid down the lines. This is a common problem, not just with these bikes.

You can do the bleeding, then tie the brake lever bake overnight, which will allow air to slowly escape and allow fluid to enter the line, then keep bleeding. Then you should be able to push the pistons out using the brake.
 

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Some of that carb cleaner has some pretty nasty solvents in it, which can damage some rubber (like your brake seals) - I am never sure what's in those so I wouldn't chance it.
 
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