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Post by jonnysquelch on Jan 28, 2014 21:43:10 GMT
I'm hoping for some help...
I have an M Reg Divi (Single front disc) and I recently changed the front brake calliper. It was sticking but that wasn't why I changed it. Anyhoo I replaced it with another front caliper (used) with plenty of copper grease and already the pistons are not returning as they should. Have I been unlucky enough to have had two sets of dodgy Callipers or is it likely to be the master cylinder? I wondered if it was a known problem.
Any help very much appreciated
Cheers
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Post by christhedivvy on Jan 28, 2014 21:46:36 GMT
I'd look into the master cyl.
Sent from my GT-I9100 using proboards
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Post by teejayexc on Jan 28, 2014 22:17:13 GMT
I'm hoping for some help... I have an M Reg Divi (Single front disc) and I recently changed the front brake calliper. It was sticking but that wasn't why I changed it. Anyhoo I replaced it with another front caliper (used) with plenty of copper grease and already the pistons are not returning as they should. Have I been unlucky enough to have had two sets of dodgy Callipers or is it likely to be the master cylinder? I wondered if it was a known problem. Any help very much appreciated Cheers What do you mean by plenty of copper grease? Copper grease should only be used on the back of the pads, red rubber grease is preferred for the seals. Could also be sticking on the slider pins, take 'em out, clean 'em up and give them a light coat of white grease, (not too much or you can hydaulic lock 'em). |
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Post by HRHpenfold on Jan 28, 2014 22:22:04 GMT
Could be the master cylinder, or the hoses breaking down, the fluid, or the caliper,
Has it got the original hoses fitted?
Has the master cylinder been serviced?
What do you mean by plenty of copper grease, where did you put the grease?
Did you clean the caliper, including the seal grooves, before you fitted it, and made sure there were no corrosion?
When was the last fluid change?
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Post by Mike D9 on Jan 28, 2014 22:22:14 GMT
I would be tempted to strip and re-build the caliper (you may have damaged seals) and put in fresh brake fluid. Recommend using red grease to lightly smear pistons and to lightly coat seals. Make sure grooves for seals clean and no salt residue. Hope this helps!!
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Post by jonnysquelch on Jan 28, 2014 22:58:54 GMT
Thanks for the quick responses :-)
The new calliper was fitted by a mechanic so my naive expression 'plenty of copper grease' was I fear, a little in accurate. The point was it's only just been fitted properly with new fluid, new seals and it's still seizing. The pipes are original but presumably I'd be loosing fluid if they were braking down? As far as I know the master cylinder has not been serviced so I'm thinking along these lines...
Thanks again
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Post by HRHpenfold on Jan 29, 2014 8:22:55 GMT
Thanks for the quick responses :-) The new calliper was fitted by a mechanic so my naive expression 'plenty of copper grease' was I fear, a little in accurate. The point was it's only just been fitted properly with new fluid, new seals and it's still seizing. The pipes are original but presumably I'd be loosing fluid if they were braking down? As far as I know the master cylinder has not been serviced so I'm thinking along these lines... Thanks again Your presumption is wrong, they break down internally and the rubber blocks the fluid returning to the master cylinder, the manufacturer's recommend that if using original type hoses that they be replaced every 3 years and yours are 20 years old, replace them even if it turns out not to be the problem, you never wait for hoses to fail before replacing, as they fail when you need them most! and don't buy the used ones of ebay, they are a minimum 10 years old! then if that doesn't cure it, then service the master cylinder! |
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Post by jonnysquelch on Jan 29, 2014 9:13:07 GMT
New hoses on the way
We'll see if that does it
Thanks again. Invaluable help and advice
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Post by bobh on Jan 29, 2014 18:14:23 GMT
It has also been known for professional mechanics to replace the seals without properly cleaning out the seal grooves, which can be quite time-consuming. If they aren't fully cleaned out the seals can bind on the pistons.
If the caliper has been properly overhauled the pistons should come out fairly evenly when you pump the lever (not too far, obviously!) and you should be able to push them back in with firm thumb pressure.
So if the problem persists after changing the hoses, check this out - it's quick and easy.
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Grumbleweed
Boy Racer
Grumbleweed, 2009 model XJ6S, brought new in 2010.
Posts: 229
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Post by Grumbleweed on Feb 2, 2014 22:09:38 GMT
When my brakes seized on my old divvy it was due to corrosion between the caliper body and the metal slidey bits that the pads sit between. The corrosion expanded (white crappy stuff) forcing the metal into the pads and locking them up. I cleaned up the aluminium, protected it and then added a little grease between the body and the metal. I probably filed off some material from the ends of the pads for good measure so they weren't tight in the slot at all.
This may not have a bearing on this case but it is worth knowing what else can go wrong.
Grum.
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Post by CD on Feb 5, 2014 1:28:36 GMT
My Divvie had corrosion in the brake caliper piston seal grooves which seriously jammed the pistons. Strip the caliper and remove the pistons. Clean the grooves and fill with red rubber grease. Fit new seals and clean off the excess grease. Refit the pistons rebuild the caliper and bleed the brake fluid. Its fiddly but the only way to be sure the caliper will work properly.
Brake hoses can collapse internally, but it's more likely to happen on car brakes (servo assisted) that run at higher pressures than bike brakes.
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midd
CBT failure
Posts: 21
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Post by midd on Mar 19, 2014 20:52:35 GMT
i had similiar problem with front calipers ,i agree with grum the slidy bits corrode behind them selves [white stuff] oxide.it sort of blooms outwards and expands . take them off polish them and clean the crud off where they sit ,make sure you put them in right way around ,i used scotch bright to get rid of the powdery oxide . mybe a little of copper slip behind them would inhibite the oxidization .i think that it will happen again eventually .preventative maintanence is the key with brakes .
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Grumbleweed
Boy Racer
Grumbleweed, 2009 model XJ6S, brought new in 2010.
Posts: 229
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Post by Grumbleweed on Mar 19, 2014 22:02:58 GMT
i had similiar problem with front calipers ,i agree with grum the slidy bits corrode behind them selves [white stuff] oxide.it sort of blooms outwards and expands . take them off polish them and clean the crud off where they sit ,make sure you put them in right way around ,i used scotch bright to get rid of the powdery oxide . mybe a little of copper slip behind them would inhibite the oxidization .i think that it will happen again eventually .preventative maintanence is the key with brakes . I used alocrom to seal the area where I dragged off the muck as I have a treatments facility at work. That and the grease meant I didn't have a reoccurrence of the problem (but the never ending clutch bearing failures ended my love with the old girl so it's somebody else's worry now!). Grum. |
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Post by CD on Mar 20, 2014 15:34:52 GMT
I tried to use pattern seals on my first Yamaha brake rebuild. They were just a touch too big and jammed the pistons. I had to repeat the job complete with a major struggle to extract the pistons. Standard Yamaha seals did however solve the problem.
Has the mechanic rebuilt the caliper?
Has he used pattern seals?
Has he perhaps fitted a used replacement that he's not rebuilt?
ANY alloy corrosion crud in the caliper seal grooves will cause the pistons to bind.
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