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Discussion Starter #1 (Edited)
Looking for some advice on my rear brake specifically the caliper.
The brake is often sticking (especially noticeable when I try to get it out of the garage) & I'm going through pads back there very quickly.
I looked at the excellent video on cleaning from Delboy's garage but immediately found problems.

Loosened the fixing bolts but I couldn't rock it back and forwards & had to use quite a lot of force from my boot to push the pistons in enough to get the caliper off.
Stripped out the pins & pads with no problems but found that one of the pistons isn't really actuating very well (I had to put the pads in again & pump quite a bit for the second one to work).
Cleaned it all up & went to push them back in & just couldn't. The only way I could to this was with a g-cramp & a socket in the piston. After it's all back together they still don't seem to work quite right. They go on but are likely to stick in position a bit (not all the way but rubbing).

I also found that I couldn't more the floating part of the caliper at all (see the pic). I assume that this part should more backwards & forwards fairly easily so the whole caliper can move.

Question here is do I need to take the whole thing apart & replace the pistons & seals or do you think there is something more going on? By which I mean do I need to get the thing reconditioned completely.

Also daft question but how does the brake dis-engage? I sort of assumed there would be springs or something to return it to position or does it rely on negative pressure from then you let go of the brake?
 

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Did you remove and clean the pistons? If not remove the caliper, leaving the brake hose connected, pump the brake pedal to push the pistons out. place a spacer, wood, socket, anything to keep one piston from coming out ahead of the other. With the pistons out clean and polish them, they probably have a varnish like crud coating. The seals will probably be ok. Don't let any oil get near the piston seals.
 

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When was the last time you changed your brake fluid? Chances are that it has not been in a very long time, in which case you probably have corrosion in the piston bores and will need to strip everything down for a proper clean. Then you should replace all the seals. Hopefully the bores and pistons will still be reusable after cleanup. The sliding pins are probably also corroded on the inside and these must be free to move so that the caliper can center itself on the disc.
Disc brakes disengage purely via piston seal tension and the miniscule runout of the disc. When you apply the brake the seal resists this movement ( which is very small) and when you release the brake the seal pulls the piston back in. As the pad wears, the distance the piston moves increases, and overcomes the seal tension by that tiny amount and so on.
 

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2008 Bonneville Black
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I'd get a rebuild kit (pistons and seals) and replace them. I don't think there's much to recondition other than that.

I did remove my caliper from the brake line so I could rebuild it on the bench. You want to get those old seals out without scratching anything. It's just a good job to do on a solid surface with good lighting. I just taped some plastic over the end of the brake line so fluid didn't drip everywhere while working.

Then bleed the brakes and replace the fluid.

One mistake that I made that cost me a pair of pads or two was putting too much brake grease on the caliper pins. You want to just cover the pins lightly. If you get all rambo and try to fill the entire cavity with grease, the pins can't move freely and you wear out the pads very fast.
 

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Discussion Starter #5 (Edited)
I did push the things out with a piece of wood blocking but they are still stiff.
Didn't think of changing the fluid, I have no idea when (& if) was last done. Might be an idea.

Ok sounds like it might be an idea to pull the whole thing out & clean. Looks like I can buy new pistons & complete seal set fairly cheaply & I know there is a how to video:
http://www.wemoto.com/bikes/triumph...tainless_steel_piston_and_seals_rear_caliper/
http://www.wemoto.com/bikes/triumph/scrambler/10/picture/rebuild_kit_full_seals_caliper_-_rear/

Question though. How freely should that top part move? I mean should I be able to slide it back & forwards or even pull out? at the moment it does not move at all that I can see.
 

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2008 Bonneville Black
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Yes, that should move freely. That is where I was talking about not putting too much grease. Sounds like it's frozen. Someone didn't grease it, or the rubber boots failed and let water in there?
 

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Back brake

I have only just completed this job myself as I had the same problem as you, in fact I have done it several times as we have two Bonnevilles in the family, so perhaps I can pass on some of my experience.

First remove silencer on the brake side, then pull calliper from disk, if it sticks just give it a bit of a knock and it will just drop off the disk, remove the pads and slide the bracket out of the pins, use a screw driver if it sticks, but it will come, the next part is the important part, do not remove the pipe that goes to the brake, place something between the Pistons and the back of the calliper (old brake pads are ideal) start pumping the back brake until both Pistons her brake pads, but most important make sure the master cylinder has got plenty of fluid in it as the level will go down as the Pistons come out, remove the brake pads and fit something else between the Pistons and the back of the calliper that is about 5mm thinner than the brake pads were, pump the Pistons out again till they touch the new spacer that you put in, you will probably have to top the fluid up again otherwise there won't be enough to pump the Pistons out, remove the last spacer you have put in and replace it with something as thin as a steel rule and pump again making sure you still have plenty of fluid in the master cylinder, the Pistons should now just pop out, clean the Pistons with metal polish if there is any corrosion on them but don't use anything else to clean them. Now we come to the main cause of the problem and that is the dust seal jamming the Pistons, what you need to do here is carefully remove the seals and you will find the grooves they fit in will have corrosion in them and muck, so make sure you scrape them out carefully, lightly oil the Pistons with brake fluid and fit them back in, you may have to give them a tap because they are very tight, just refit everything else and refill the master cylinder and bleed the brake, and you are done. I usually find you can reuse the seals although you are not to supposed to if you take them out carefully.

Plasma
 

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I'm about to rebuild my rear caliper. Got the OEM pistons and seals from Hermy's Triumph (triumphestore.com). I also got a jar of brake assembly grease, as I read that it's recommended to use that upon assembly.
 

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I recently noticed my rear brakes must have been dragging or stuck for a while.The inner pad was worn while the outside pad was fine.Only 7,000 miles on the bike and I am not that big a user of the rear brakes.I don't ride or brake hard.The front pads are fine. When my bike was in for service recently I told the service guy I need new pads because they are dragging or stuck. Got the bike back with new pads but no mention of any fix of the dragging or stuck problem on my receipt. I had it up on the center stand the other day and spun the rear wheel and it still seems like it is dragging a bit.
 

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Discussion Starter #13
Got through the the refurbishment today but was wrong in my expectations. I watched the utube clips on how to do it & it took them about an hour so I estimated two hours. I told my wife who then laughed & said four hours then... I think we all know who was right in their estimation (sigh).
Some real problems though. Whoever had been at it before had stripped the banjo which was a sod to get off. The whole mechanism was completely seized & it took me ages to get apart & clean. There was so much crap in there I was worried I wouldn't be able to clean it.
Finally took it down to my local bike shop to get a new banjo & they lent me a couple of hooks to get in & clean the seal grooves & they managed to find a banjo on no notice. Big up to the guys, especially Adrian at Carl Rosner in South London (Sanderstead) for their help here.
Got it all cleaned. New seals & pistons but then found out that one of the mounting bracket seals was wrong so had to nip down to Rosners again to order a new one. At the moment it's packed with red rubber grease.
Took it for ride & finally works as I'd expect, just took a loooong time to sort.
BTW thanks for all the advice here as well ?
 

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Things take time, they sure take me a lot of time. Point is, you got it done. Add "rebuilding calipers" to the list of things you know how to do and reward yourself with a beer and/or a steak or something ;)
 

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Things take time, they sure take me a lot of time. Point is, you got it done. Add "rebuilding calipers" to the list of things you know how to do and reward yourself with a beer and/or a steak or something ;)
Or, "talk" to your wife. Beats a steak every time :surprise::YellowWow
 

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I recently noticed my rear brakes must have been dragging or stuck for a while.The inner pad was worn while the outside pad was fine.Only 7,000 miles on the bike and I am not that big a user of the rear brakes.I don't ride or brake hard.The front pads are fine. When my bike was in for service recently I told the service guy I need new pads because they are dragging or stuck. Got the bike back with new pads but no mention of any fix of the dragging or stuck problem on my receipt. I had it up on the center stand the other day and spun the rear wheel and it still seems like it is dragging a bit.
Hi , I recently had a situation where the rear disc of my 2003 Bonnie made a horrid noise . One pad lining was found to be completely shot (metal to metal contact) while the other lining was virtually untouched. The caliper had been unable to float on the pins of the bracket (various names on the net, Delboy calls it a slide carrier) that it is mounted on. Therefore only one pad had been doing all the work. Thankfully the disc wasn't badly scored and a bit of an emery tape polish cleaned it up. It took an age of frustration to get the caliper off the pins . I made a steel plate up and bolted it to the to the bracket through the two mounting holes that are in it. With the muffler removed, and the caliper on a block of wood for support, piston pressure and dozens of careful taps on the ends of the steel plate were used to eventually push/drive the bracket pins out of the caliper. The bottom pin was particularly rusty. Both pins were cleaned up , not forgetting to thoroughly clean out the pin bores in the caliper. Hi temp grease / red rubber grease were used to reassemble. Check out Delboy's Garage :
After a test ride of a few miles (not using the rear brake) the disc was found to be almost cold so the caliper must be floating as it should. The back wheel can be locked up no problem under hard braking so all works well. The front caliper ( working fine) will be done soon as a precaution and I will put strip/check/grease calipers into my maintenance schedule.Obviously this has been neglected by past owners. I have seen a lot of talk about pad pins but not so much about the caliper bracket / pins. Hope this helps someone out there. Ride safe !!
 
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