Well, I'm replacing my rear brake pads. I got the old ones out just fine. I'm at the part where the Haynes manual says "push the pistons as far back into the caliper as possible using hand pressure only".
Well, that's not even close to far we enough. I removed the reserve cover and diaphragm off the reservoir. It says to siphon off fluid? Will that matter?
I even cheated and used vice grips trying to push those suckers back, but the pistons just won't back up. I opened the bleeder port and let a bit of fluid out that way, too....no better results.
I'm stuck. Suggestions?
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Quote from: PantheraLeo on January 26, 2015, 02:26:15 PM
Well, I'm replacing my rear brake pads. I got the old ones out just fine. I'm at the part where the Haynes manual says "push the pistons as far back into the caliper as possible using hand pressure only".
Well, that's not even close to far we enough. I removed the reserve cover and diaphragm off the reservoir. It says to siphon off fluid? Will that matter?
I even cheated and used vice grips trying to push those suckers back, but the pistons just won't back up. I opened the bleeder port and let a bit of fluid out that way, too....no better results.
"Using hand pressure only" is certainly the
safe to do it, but as you have learned ... sometimes it just doesn't work.
To be clear, did you have the bleeder port open
while you were trying to force the pistons apart? To prevent air from getting in the system when you do this, you can try pushing a straw or a short length of tubing onto the bleeder port. Once fluid escapes the system, it almost
never makes its way back in, so this method should keep the port submerged in brake fluid.
(http://bbburma.net/MiscFotos/100_2215_BrakeBleeding_StrawAndPaperCup_1.jpg)
(http://bbburma.net/MiscFotos/100_2216_BrakeBleeding_StrawAndPaperCup_2.jpg)
(http://bbburma.net/MiscFotos/100_2220_SpeedBleederBag_2.jpg)
(http://bbburma.net/MiscFotos/100_2221_SpeedBleederBag_3.jpg)
It's been a while since I worked on my rear brakes, but I can remember forcing the pistons apart with a large screwdriver ... by inserting the screwdriver between them and alternately tilting it towards me and away from me.
I don't think I ever had to resort to
ViseGrips or clamps on the rear caliper, but here is a photo of a related method that I used on my front caliper more than once
(Notice the 1x2 board! You DON'T want to apply a concentrated force -- via a small C-clamp pad, say -- against the body of your caliper. There's a good chance you would put a hole right through it.)
(http://bbburma.net/MiscFotos/100_1225_FrontCaliper_CompressPistons.jpg)
Never had a problem with a motorcycle master cylinder riding year around here in NE Ohio for 30 years and over 400k miles on 4 Hondas and 2 GS500s. But wheel cylinders have had sticking problems caused by crud built up on the pistons and by the the outer wiper lips being rolled over, sticking shortly after changing pads.
Since shortly after I got the 1st GS I have always popped the pistons out to clean them with SOS type steel wool pads or those green kitchen pads. Always. Also I always remove and throw away those outer wipers after the first or second pad change/piston cleaning. They will wipe the brake dust off when pushing pistons back while changing pads but serve no purpose with a thoroughly and properly cleaned piston and they won't touch that hard crud that builds up on mine.
Never had a problem with pushing pistons back into the seals, I use lots of brake fluid to lube. Filling the bore with brake fluid up to seals before pushing the pistons in with bleeder open greatly reduces bleeding time too. The dust seals don't do anything for you if you don't push dusty dirty even hard packed crud like pistons like I get back into them without cleaning pistons. I've never replaced piston seals in any calipers putting 80-100k miles on 4 of the 6 bikes I've had, 2 of the Hondas and 2 GS500s.
I decided to bite the bullet and pull the calipers apart. A long bleeding journey is in front of me. They were not gonna recede without it.
I've got them reassembled. Too much air in them to push back together. But, I know what I've gotta do now.
Oh well. Its done.
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When I replaced my rear pads, I used a long flathead screwdriver to lever the pistons back into the calipers on my GS.
Thanks for the tips. I did give the pistons a good scrubbing while I had them out. They were pretty grime coated, and I'm sure these were the original pads on my '05. I've been avoiding brake work, so I got a complete look at the whole system on this pad change-out. By the way, there are two YouTube videos on the subject. Both are horrible.
The Haynes manual was pretty useless once the pistons failed to cooperate. I did understand basic hydraulics well enough to open the bleeder while trying to push the pistons back. All in all, I'm okay with doing a complete caliper break down and cleaning. I doubt I will need to touch these rear brakes again on this bike....but if I do I'm ready.
Oh, I used the old pads to disperse the area I was pressing down on with my vice grip jaws. I liked that C-clamp setup, Kerry!
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I've done 10 front and 15 rear pad changes on my 97 and 02 GSs over 15 years and 180k GS miles. Plus more recently at approx 99k miles on the 02 I replaced both calipers with low mileage ones from a 09. Practice makes perfect. :icon_lol:
http://img.photobucket.com/albums/v443/jcp8832/GSbrakechainlog_zps1b8c96a9.jpg
Quote from: gsJack on January 27, 2015, 04:48:46 AM
I've done 10 front and 15 rear pad changes on my 97 and 02 GSs over 15 years and 180k GS miles. Plus more recently at approx 99k miles on the 02 I replaced both calipers with low mileage ones from a 09. Practice makes perfect. :icon_lol:
http://img.photobucket.com/albums/v443/jcp8832/GSbrakechainlog_zps1b8c96a9.jpg
Its funny. In October, I had never touched a bike. Changing the oil the first time scared the piss out of me...now I see that a brake assembly is really just a very simple device. Pedal pumps a piston which drives brake fluid to bigger pistons. Who knew? Well, a lot of you did, but I digress....
Every time I dig into the next bike project, it is never as bad as I worried it might be. I'm no expert, or even a good mechanic, but on this bike I keep managing to be "good enough". Its a pretty damn fun bike to work on.
This has been a unanticipated enjoyable activity from owning my GS. I believe understanding the parts of the bike will make me a better rider.
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Quote from: PantheraLeo on January 27, 2015, 12:42:42 AM
Thanks for the tips. I did give the pistons a good scrubbing while I had them out. They were pretty grime coated, and I'm sure these were the original pads on my '05. I've been avoiding brake work, so I got a complete look at the whole system on this pad change-out. By the way, there are two YouTube videos on the subject. Both are horrible.
The Haynes manual was pretty useless once the pistons failed to cooperate. I did understand basic hydraulics well enough to open the bleeder while trying to push the pistons back. All in all, I'm okay with doing a complete caliper break down and cleaning. I doubt I will need to touch these rear brakes again on this bike....but if I do I'm ready.
Oh, I used the old pads to disperse the area I was pressing down on with my vice grip jaws. I liked that C-clamp setup, Kerry!
IMPORTANT!!!!
If you have cleaned everything and got it up to snuff and you still have to open the bleeder to retract the pistons.
You may have a bad brake hose that is not letting the fluid return to the reservoir.
It will act like a check valve and you will have pressure on the pads when you are not applying the brake.
I had that on my 89 and had to replace the flexible hose. Probably not an issue on your much younger bike.
regards
mech
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Quote from: Old Mechanic on January 27, 2015, 04:54:50 PM
IMPORTANT!!!!
If you have cleaned everything and got it up to snuff and you still have to open the bleeder to retract the pistons.
You may have a bad brake hose that is not letting the fluid return to the reservoir.
It will act like a check valve and you will have pressure on the pads when you are not applying the brake.
I had that on my 89 and had to replace the flexible hose. Probably not an issue on your much younger bike.
regards
mech
I actually used the spinning wheel from the centerstand test to verify that the rear brakes were retracting and compressing. I haven't road tested it just yet, but the wheel stops very quickly (and quietly) now with the new pads and the system bled. When I release the pedal, the tire spins freely and has no brake drag.
I am planning on taking it on a short test ride this afternoon to
carefully verify proper road operation.
Quote from: PantheraLeo on January 29, 2015, 12:15:53 PM
Quote from: Old Mechanic on January 27, 2015, 04:54:50 PM
IMPORTANT!!!!
If you have cleaned everything and got it up to snuff and you still have to open the bleeder to retract the pistons.
You may have a bad brake hose that is not letting the fluid return to the reservoir.
It will act like a check valve and you will have pressure on the pads when you are not applying the brake.
I had that on my 89 and had to replace the flexible hose. Probably not an issue on your much younger bike.
regards
mech
I actually used the spinning wheel from the centerstand test to verify that the rear brakes were retracting and compressing. I haven't road tested it just yet, but the wheel stops very quickly (and quietly) now with the new pads and the system bled. When I release the pedal, the tire spins freely and has no brake drag.
I am planning on taking it on a short test ride this afternoon to carefully verify proper road operation.
always pump both brakes after replacing EITHER sets of parts:
first to verify the calipers have extended the pistons (doh!) and
second to ensure nothing goes POW the first time you come to a stop sign.
i've picked up bikes from shops before and not realized there are no caliper bolts holding the calipers in place. never ever trust anyone else's work, and ALWAYS double check your own. brakes matter :)