Binding rear brake!!

Not having much luck! I now seem to have a binding main rear brake. I cleaned it all out & polished the outer surfaces of the pistons. That's when I thought the parking brake was the culprit! Thanks again to all who helped there.

It's worse after I start the bike because, as you all know, you gotta squeeze that brake quite a lot to activate the starter circuit. That's when she is binding tight. Now, a few thumps on the calliper with a gloved fist or a light rubber mallet does the job and after a short distance it's freed up but after I use the brake a few times it tends to lightly bind again.

I need to change brake fluid in both brakes so was thinking of I taking off the rear calliper completely for attention. Any advice anyone? Perhaps replace all seals, pull the pistons out and really polish them?

Cheers

Martyn

I think you're right, pull it off for a clean up. You may just need to clean the pistons and lubricate the pins that the callipers slides on. The seals may well be fine.

I had some similar issues which were solved by magic when I returned to OEM brake pads.Aftermarket ones were worn unevenly.Probably were stucked due to a unappropriate shape.Keep in mind ,every time you change the pads don't forget to clean the pistons with some brake cleaner and a tooth brush,before you squeeze them back into the caliper.

Thanks guys. I did clean the pistons with cleaner and a wee brush and they were moving fine before I remounted the calliper. And I greased those pins. Like I said, the fluid needs changed so here's an opportunity to give it another blatter. I have some nice new pads in my cupboard too, maybe I'll shove them in for good measure. Cheers

I haven't looked at the brake calipers on the SW very closely but on GWs it's not uncommon for calipers to freeze. The caliper must be free to move from side to side on it's mounts, that's how pistons on one side only can press both pads to the rotor. If the sliding mounts of the caliper become corroded they won't slide and the caliper will retain pressure on the pad on the opposite side of the pistons. The normal cure is to remove the caliper and clean the mounting bolts and pins as RArch already mentioned. Pistons don't normally cause the problem you're describing.

Just as a reminder for anyone who isn't familiar with disk brakes, unlike shoe type brakes that pull the shoes out of the drum when you release the brakes, disk brake pistons relieve the pressure in the disk when released but do not pull back the pistons or pads. The pads normally ride in light contact with the disk. If one pad is held against the disk due to caliper being frozen in its mounts the brake will heat up and add even more pressure to the disk to to heat expansion.

exavid wrote:

I haven't looked at the brake calipers on the SW very closely but on GWs it's not uncommon for calipers to freeze. The caliper must be free to move from side to side on it's mounts, that's how pistons on one side only can press both pads to the rotor. If the sliding mounts of the caliper become corroded they won't slide and the caliper will retain pressure on the pad on the opposite side of the pistons. The normal cure is to remove the caliper and clean the mounting bolts and pins as RArch already mentioned. Pistons don't normally cause the problem you're describing.

Just as a reminder for anyone who isn't familiar with disk brakes, unlike shoe type brakes that pull the shoes out of the drum when you release the brakes, disk brake pistons relieve the pressure in the disk when released but do not pull back the pistons or pads. The pads normally ride in light contact with the disk. If one pad is held against the disk due to caliper being frozen in its mounts the brake will heat up and add even more pressure to the disk to to heat expansion.

The SW has a similar setup. To release pressure off the rotor when removing pads the service manual informs the user to apply pressure to the area the pistons are located to remove the pads from contact with the brake rotor.

Exavid, thanks for that info. It should have been obvious I guess but I had fallen into the trap of assuming the pistons did all the work! I can see clearly now what the likely problem is after your description. Righto, I'll pull the pins and clean and lubricate. Cheers

Martyn

Remember to Let us all know the cause and solution

Well guys I took the floating pins out and boy the bottom one needed cleaned. Wire brushed then shiny, greased and replaced. Calliper floated back and forth lovely under light hand pressure. Replaced pads, pumped up brake pressure and STUCK wheel! Light tap with a hammer on outer case of calliper over the pistons, wheel free. And so it went! So, the pins are all clean and lubricated so the pistons must be the culprits. Back out with the tool box!!

Oh, d'ya think new pads would make a difference? If so, why? Current ones are only about half worn.

My front and back brakes are like new engine does most of the work .Keep the old ones for spare ,but you may never need them again.

Wild guess... Have they worn side ways due to the corroded pin and now jam up on the pins?

If you have new pads it wont hurt to fit them.

It may be a long shot, but here is what I believe cured mine. I too was having my rear brake bind up. After new pads and a caliper clean which it needed, I replaced the brake fluid. After several attempts to get a good bleed I found my front bleed screw to be drawing air (Brake vacuum would not hold). I sealed the front bleed screw with some Teflon tape and the bleed sequence was successful. I assume you know that the front and rear brakes are linked?

Well, had the calliper off again, pistons out, cleaned and shined. There's a bit of pitting/corrosion on the lower piston, which doesn't seem to move as much as the top one. Thin smear of copper grease, popped back in, changed brake fluid & bled and a measure of success.

It doesn't lock almost solid when the brake is squeezed enough to activate the starter but it does still bind a bit. When I got the bike, the rear wheel used to turn freely when on centre stand and engine running. Now it doesn't.

I felt the rear brake lever used to feel a bit 'heavy' but never having used linked brakes before I wasn't sure if this was normal or not. Now it moves much more freely but still some bleeding needing done I think. I have a "Vizibleed" one-man bleeding kit I used to use with the Beemers. I thought I had it all pumped through and expelled all the air (inc at the front lower piston) but obviously not. Doesn't feel spongy as such, just weak. Anyway, enough for today, it's COLD out there!

There shouldn't be any drag on the wheel when hand turning other than the belt. Try squeezing the brake on releasing it, then when it's dragging try rotating the wheel back and forth to see if the wheel frees up. I wonder if there's something bent in the caliper or it's mount. Can you push the pistons back into the caliper with reasonable effort? I've seen some pretty pitted pistons that still worked okay. I forgot whether you said you've replaced the seals in the caliper. If those get age or heat hardened it might bind the pistons.
It sure can be frustrating trying to diagnose a problem that you can't see.

I'm not able to hand push the pistons back even with the master cylinder lid off however they do move much more easily with a G clamp than they did originally. Also, the top piston is moving much freer than the bottom one. Nothing else for it I think than to replace seals at least. Don't know how the caliper or mount would be bent, nothing has happened to the bike to cause any such thing. This seems to have snuck up on me. Perhaps the brake was under performing before hand due to it's long inactivity under previous ownership and the binding, as you say, has heat damaged the seals. The brake felt fairly effective previously anyway. Ho Hum!

Right, piston seals replaces (£20 from Mr Honda) and it's a lot better but still not as free as I'd like, but definitely a great deal better. Bled the brake lines but the lever is still spongy. I guess it will need more time spent on that.

You've got me thinking about mine now!

How free does you're wheel spin, when I turn mine by hand it will not run on by itself.

FWIW Those rear caliper pistons are interchangeable...aaand you should only lube the pistons, caliper bores & piston seals with brake fluid. However the dust seal is lubed with waterproof silicone.

Dunno if that copper grease will contaminate the brake fluid.

Pistons etc all cleaned again of copper grease. Turns out the upper dust seals on both had vanished! I wondered why there was what appeared to be a seal groove but no seal.

I guess I just need to be patient and keep bleeding the calliper until I get decent pressure. Since both pistons were out, probably some air trapped in it. The fluid has been renewed by now with all the pumping I've done!

My wheel will move ok by hand and I realise there will be drag due to the drive belt. I just don't feel it's as free as it should be (but very much better than it was) and seem to remember seeing it rotate on it's own when on the centre stand and the engine running. Maybe it's fine. Just have to carry on the tedious task of brake bleeding!

Try some grease around the nipple to seal it when bleeding in case its drawing some air in...

Anybody else check their tyres, how does the back wheel spin for you?

The back wheel spins with a little resistance due to all the gearing inside the casing.If you get 1/2 a turn of the wheel or more your fine.The brakes have a spongy feeling on the duel brakes and front to activate all the switches and the ABS system . Ride at a crawl and touch the left lever and see what happens.You might slide of the the seat.

Coincidentally, I was just spinning my rear wheel (2004 ABS) the other day. While pushing the scoot to move it out of the way, I had noticed that it seemed harder to move so when I got it back on the center stand I gave the wheel a spin. Definitely some resistance, I would say 1/2 turn that Tinman mentioned is about right. I wonder if the belt resistance is more in cold temperature?

-Gary M

Belt resistance? Now there's something I never thought of! Goin to do some more bleeding! BTW mine is a 2001 NON ABS model. Keep you all posted.

Well, bled both ends til I saw no air comin out at all. Still cant get full pressure AND the blasted calliper is still binding! Not as bad as before but it still is. After a very short jaunt of around 500m the rear brake disc was very hot!

I think the only thing for it is a replacement brake calliper. Any UK or Ireland members know any sources for good quality used Honda parts?

Feck it... Have you got a good front brake since they are linked maybe its the front one that needs bleeding.

I don't think spinning the back wheel turns the belt, theres a clutch in between. If it did we may be able to bump start the scooter which we cant.

You've rebuilt the brake caliper! I cant see buying a 2nd hand one being a fix, could a wrapped disk be causing your problem? Try ebay maybe...

As for spinning by hand I'd have to go some to get my wheel to spin half a turn! You'll have me taking mine apart next weekend

Maybe its time to take it to a bike shop for a mechanic to take a look...

RArch, I did not mean that the belt would move when spinning the rear tire by hand; only that the belt is sitting loosely in the clutch so there would be some slight friction there. My Tao Tao 50cc (same kind of CVT but smaller) feels exactly the same resistance in the rear as the SWing. Not spinning freely by any means.

-Gary M

Sounds like a warped disc. Considering the tolerances, it may not be noticeable to the naked eye. Since there is a bit of the disc visible, try taking a straightedge, (ruler or level maybe) and placing it on the disc. That may give you an indication if it is warped.

Dramhunter wrote:

Well, bled both ends til I saw no air comin out at all. Still cant get full pressure AND the blasted calliper is still binding! Not as bad as before but it still is. After a very short jaunt of around 500m the rear brake disc was very hot!

I think the only thing for it is a replacement brake calliper. Any UK or Ireland members know any sources for good quality used Honda parts?

Obvious place - Ebay.

Then try Lings, (Mr Google works here) I'm at work so cant get the link as easily as I can at home!!! I got the rear wing circa £300 for £20!!!! (Used but very good)

Thank you all. Tried Lings last night, they don't have one. No joy on eBay either. Anyone know what other bikes use the same calliper?

I'll check the brake disc, I was beginning to suspect that but until quite recently things had been spot on, can't think what would have warped it. This appears to have occurred quite rapidly. Perhaps new pistons?? The ones in her look pretty clean on their outside surfaces with just a small bit of corrosion near the top edges. When I was putting them back in after replacing the seals I did have to use a G Clamp to help (thumbs weren't up to it) but they seemed to slip down very easily with it. Should it need only thumb pressure?

The front brake, when pulling the right lever alone, is working fine with good pressure. I know the lower piston on the front is part of the linked mechanism and I've bled through it's nipple also. I'll have a go at bleeding the top one in case some air has migrated. Feels like chasing shadows!

cheers

Bleed the whole system again, in the correct order.
Front top nipple first using the right master cylinder.
Front bottom nipple next, using the left master cylinder.
Rear nipple last, using the left master cylinder.

Did as Rollsroyce250 suggested. Got a deal more air out but no change, no improvement in pressure. A fair bit of air came out of the front top nipple which is weird because that brake was fine and with good firm pressure until I began this last process and now it's spongy too!

And the rear brake continues to bind. From observing with a lamp it seems to be the outside pad that is dragging on the disc, the inside one seems to have a small gap between it and the disc. I'm stumped, I'll just have to pay someone to sort it.

You have us all stumped

So the disk doesn't looked warped?

Clutching at straws now...

What about wheel bearings, is there any lateral movement in the wheel?

Wheel spacers, is it possible you are missing or have an extra one moving the disk out of line?

Check again if all parts of the caliper are on.There is also a lamina squeezing both pads downwards and a chrome part that places pads to their stop position and sometimes they fell of the caliper easily.The last one has to be bended in order to stay in place.Check them out on the parts list(Number 3 and 4 page 2-38 rear brake caliper)

If you have some free spine,go for a good ride then smell the brakes ,touch the disk for heat ,If you can keep you hand lightly for a few seconds ,keep riding ,It might settle down.

Are the pads OEM Honda, or replacements like EBC?

When you had the calipers out did you clean the grooves that the two seals go into? I've seen gunk in the corners of the grooves build up and cause some binding of the piston when new seals were installed. Crud in the bottom corners of the groove prevent the seal from seating all the way down in the groove which will tend to make the seal press against the piston excessively.
One cause of difficulty bleeding the brakes on Honda bikes is the small port in the master cylinder. If you take the lid off the master reservoir you can see a hold in the bottom and a little metal disklike cover over another hole. One hole looks like it's dead ended but there's a very small hole in the bottom. If that hole gets plugged it's nearly impossible to bleed the brakes and it can also cause the piston to bind on the caliper because the brake line pressure can't be relieved. I use a whisker from a wire wheel held in a pliers or vise grip to poke out the hole. If you have dirty brake fluid it's very likely this needs being done.
One test you can do which I forgot to mention earlier is when the brake is dragging, crack open the bleed nipple just a bit and see if that relieves the drag on the wheel. If it does it's very likely the small port is plugged. This port getting blocked is fairly common on any bike that doesn't get it's brake fluid changed ever couple of years. Also since brake fluid is very hydroscopic and is designed to absorb water, always use a fresh can of fluid to be sure it doesn't have any moisture in it.

BTW - Pad thickness doesn't usually matter with brake drag, it happens with old worn pads as well as new ones. I've never had a problem using EBC organics on Goldwings. I don't like the metal sintered ones because the do wear the disk more rapidly.

Exavid, I'll look into what you mention, thanks. Tinman, I'll try that too but a 500m jaunt made the disc quite hot. As this binding began before I disassembled the calliper I don't think any missing parts are to blame. It's been suggested by a mechanic that I suck the fluid out rather than pump. I remember having to do that on my old Beemer so I'll give it a whirl. The pads are barely worn and the seal grooves were all scraped out before I put the new seals in.

Thanks again guys.

I've used a cheapo 100 ml plastic syringe to suck old brake fluid from the reservoir when bleeding brakes.

At the bottom of the caliber there is a pad pin to keep the pads in line, there could be a ber when the holes were punch out ,check if there is free play or a scored pine It could that stop the pad to fully re track.

Thanks Tinman but the calliper floats back and forth freely under light hand pressure before pads are installed. I'll see what happens after I get the syringe on her and after cracking open the bleed nipple in the way Exavid described. I'll keep everyone posted.

Cheers

Have you ran a test on the disc for alignment?

Someone mentioned earlier regards a warped disc. Worth checking before throwing more time and resources at pads, callipers and bleeding!

Well I'm stumped. There appears to be an enormous amount of air in the front brake now, much, much more than before. Bleeding again from front top to front bottom to rear. Could not get air to come out of the front top nipple, lever just pumped and nothing happened. Got some more out of front bottom and the rear, bit more pressure but the front is dead. Weird because that brake functioned fine before!

Tried sucking fluid through with a syringe but there was an enormous amount of negative pressure then the rubber seal in the syringe dissolved by the brake fluid! I'll just have to take it to a mechanic, mu knowledge is exhausted.

Try leaving the reservoir lid off over night to see if the bubble will work its way back .Or crack open the bleeder and let gravity do its work.

Righto Tinman, cheers. Tomorrow is my last offensive on this, after that I'll just have to admit defeat and leave it to an expert.

Well, used a combination of syringe to suck and one way valve to pump and got full pressure back in the front brake and better pressure in the combined back/front. Jeez how'd SO much air get in?!

Put in new brake pads, ensure the calliper slid freely on the float pins, applied brake pressure and it still drags! Honda belfast tells me that the combined brake system on the 2001 machines has a pressure balancing valve which may be the culprit!

If nothing else your persistence is most admirable.

I would have thrown heavy objects all over the place by now.

Waspie, you should have heard my invective today!!

Now I have admitted defeat, it will have to go to an expert. I removed the calliper again and pumped the lever. Only the top piston moved, bottom one didn't budge. Even with the fluid reservoir off it was very difficult to push that piston back with thumbs. Very still.

When I clamped the top piston, the bottom one would move when the lever was pumped. Again, very very stiff to push back. Both pistons would NOT move together when the lever was pumped and that seems totally wrong to me. I now seriously wonder if that pressure balancing mechanism is kaput.

Thanks to everyone. When I've paid a chap to sort it I'll report on what the problem was.

What kind of grease did you use, and what brake parts did you use it on?

It's normal for one piston to move before the other. There always will be a slight difference in friction between the pistons and their cylinder bores. Once the faster moving piston starts pushing it's pad into the disk the other(s) will catch up. It's normal.