brake issues after freeing up bobbins.

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fatfreddy000
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brake issues after freeing up bobbins.

Post by fatfreddy000 »

hi again all,
more questions..
So it seems that freeing up the disc bobbins has certainly done something..
the front wheel doesn't have any tight spots when rotating now, which is great, but the brakes are much softer- that is the lever needs to travel much further before the pads begin to engage and i feel any resistance on it or any braking effect on the the front wheel..
i thought that the pistons would just readjust and take up any slack if this was necessary?
i am unclear why this has happened but i will try and bleed the brakes when i next get the chance and see if theres any air or dirt in there..
any suggestions welcomed- of course a complete strip and new parts would help but trying to avoid too much money and time as i have neither at present (last £250 will be spent on getting the terrible forks rebuilt by roger and replacing the headstock bearings)..
in addition the rear brake is really tight- the pedal only moves a tiny wee bit before absolute resistance is met, so that you really have to push hard if you want significant braking on the back wheel.. a proper stomp to lock it.
i think with the back wheel i will buy a new seal kit and change the fluid and see how that goes, but again any suggestions much appreciated..

.. oh dear, my wallet is empty!
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tony.mon
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Re: brake issues after freeing up bobbins.

Post by tony.mon »

Bleed front brakes, strip and rebuild back brakes then bleed that one the fresh fluid helps
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fatfreddy000
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Re: brake issues after freeing up bobbins.

Post by fatfreddy000 »

found 20mins spare and just bled the front brakes. no air bubbles in there but just filthy fluid. all fresh now and working much better.
had a look at the piston in the rear single pot calliper and i can see from the edge thats showing that its horribly rusted up so probably a new piston and seal kit rather than just the seals then fresh fluid..
just looking forward to having it road worthy and going for a blast but one thing at a time..
“If all insects on Earth disappeared, within 50 years all life on Earth would end. If all human beings disappeared from the Earth, within 50 years all forms of life would flourish.” Biologist Jonas Salk
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fabiostar
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Re: brake issues after freeing up bobbins.

Post by fabiostar »

fatfreddy000 wrote:found 20mins spare and just bled the front brakes. no air bubbles in there but just filthy fluid. all fresh now and working much better.
had a look at the piston in the rear single pot calliper and i can see from the edge thats showing that its horribly rusted up so probably a new piston and seal kit rather than just the seals then fresh fluid..
just looking forward to having it road worthy and going for a blast but one thing at a time..
push the rear piston out and give a clean with some v fine wet and dry.. strom rear brakes are sh1t at the best of times
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fatfreddy000
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Re: brake issues after freeing up bobbins.

Post by fatfreddy000 »

fabiostar wrote:
fatfreddy000 wrote:found 20mins spare and just bled the front brakes. no air bubbles in there but just filthy fluid. all fresh now and working much better.
had a look at the piston in the rear single pot calliper and i can see from the edge thats showing that its horribly rusted up so probably a new piston and seal kit rather than just the seals then fresh fluid..
just looking forward to having it road worthy and going for a blast but one thing at a time..
push the rear piston out and give a clean with some v fine wet and dry.. strom rear brakes are sh1t at the best of times
guess i may as well give it a try before shelling out more money..
will do that and change the fluid and let you know what happens.
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agentpineapple
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Re: brake issues after freeing up bobbins.

Post by agentpineapple »

fatfreddy000 wrote:found 20mins spare and just bled the front brakes. no air bubbles in there but just filthy fluid. all fresh now and working much better.
had a look at the piston in the rear single pot calliper and i can see from the edge thats showing that its horribly rusted up so probably a new piston and seal kit rather than just the seals then fresh fluid..
just looking forward to having it road worthy and going for a blast but one thing at a time..
i might have a spare rear piston you can have mate, i'll have a little hunt for it
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Re: brake issues after freeing up bobbins.

Post by firestorm_al »

Spongy feeling on the front brake can be down to one or more of the pistons sticking in the caliper. Periodic cleaning of the calipers and pistons is a must (especially riding up here in Scotland).

Only take one caliper at a time and with four pot calipers try and work on only one side of the caliper at the one time. I.e. only try and let the pistons at one side move when you are working on them (easier said than done).

I have buy Wurth brake cleaner in bulk and use a pump sprayer rather than use aerosols. I also keep a small container of brake fluid specifically for cleaning pistons. I use brake fluid as it is compatable with the

Clean all the dirt you can off of the caliper using brake cleaner and a tooth brush before you work on the pistons. Extend the pistons carefully out from the caliper body just enough so you can, hopefully, see shiny clean metal apearing. Using the brake fluid and cotton buds give the pistons a good clean to remove any deposits. Sometime what look like massive rust spots can be reduced significantly.

Once the pistons are clean carefully push them back in. Hopefully if the cleaning has donw the trick they should move back fairly easily. Just keep an eye on all of the pistons as you are doing this to make sure that all the pistons don't come out too far.

Al.
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fatfreddy000
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Re: brake issues after freeing up bobbins.

Post by fatfreddy000 »

firestorm_al wrote:Spongy feeling on the front brake can be down to one or more of the pistons sticking in the caliper. Periodic cleaning of the calipers and pistons is a must (especially riding up here in Scotland).

Only take one caliper at a time and with four pot calipers try and work on only one side of the caliper at the one time. I.e. only try and let the pistons at one side move when you are working on them (easier said than done).

I have buy Wurth brake cleaner in bulk and use a pump sprayer rather than use aerosols. I also keep a small container of brake fluid specifically for cleaning pistons. I use brake fluid as it is compatable with the

Clean all the dirt you can off of the caliper using brake cleaner and a tooth brush before you work on the pistons. Extend the pistons carefully out from the caliper body just enough so you can, hopefully, see shiny clean metal apearing. Using the brake fluid and cotton buds give the pistons a good clean to remove any deposits. Sometime what look like massive rust spots can be reduced significantly.

Once the pistons are clean carefully push them back in. Hopefully if the cleaning has donw the trick they should move back fairly easily. Just keep an eye on all of the pistons as you are doing this to make sure that all the pistons don't come out too far.

Al.
Thanks for that.
How do you keep the 2 pistons on one side from moving. Maybe something like a strip of metal and 2 clamps?
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Wicky
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Re: brake issues after freeing up bobbins.

Post by Wicky »

Put something thin between the two pistons. They should come out equally if they don't then seals are shot and the callipers need a thorough overhaul.
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fatfreddy000
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Re: brake issues after freeing up bobbins.

Post by fatfreddy000 »

fabiostar wrote:
fatfreddy000 wrote:found 20mins spare and just bled the front brakes. no air bubbles in there but just filthy fluid. all fresh now and working much better.
had a look at the piston in the rear single pot calliper and i can see from the edge thats showing that its horribly rusted up so probably a new piston and seal kit rather than just the seals then fresh fluid..
just looking forward to having it road worthy and going for a blast but one thing at a time..
push the rear piston out and give a clean with some v fine wet and dry.. strom rear brakes are sh1t at the best of times
Cleaned up the rear brake piston and the sliders and everything I could. The caliper is missing the front upper rubber off the 'slider'.
The brake is still solid, that is there is barely any movement between off and fully depressed but the effect
on the back wheel is much more positive and i can lock it without a full on stomp.
The front brakes are still too soft.. Not spongy as such just that there's too much play on the lever unless I pump it a couple of times, I reckon that cleaning up the pistons will improve things considerably.
“If all insects on Earth disappeared, within 50 years all life on Earth would end. If all human beings disappeared from the Earth, within 50 years all forms of life would flourish.” Biologist Jonas Salk
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