Shimano Brakes losing power after bike sitting idle

[krezi]

Hey Guys,


It's been going on for a couple of years with various intensity that after bike is sitting idle in the shed the brakes lose power and feel and squeal. The brakes are bled and there is no oil residue or contamination.


Normally I would take out the pads clean them with disc brake cleaner then sand them and out back in. Many time when I start riding and some grit gets into pads the feel and power comes back etc.


It's just annoying that you leave bike with perfectly working brakes after a ride and then comes time to ride again and you need to include this maintenance before riding.


How do you guys tackle this issue? Read about pads blow torching, baking etc


Thanks
Pawel

[feed]

Yup, some Shimano brake caliper leak tiny amounts of oil which isn't  an  issue with regular use as it burns off but if left sitting for a while ends up with brakes that squeal like a banshee and are as effective as a 1970's council worker.

To remedy I take the pads out, use washing up liquid and rub the contact surface of the pads against each other until the suds no longer are black. If badly contaminated I normally take off the rotors and scrub with washing up liquid and nail brush.  That's normally enough to get them back to 100% (after a bit of hard breaking). I  have had pads that were so badly contaminated that that wasn't enough. On those occasions I use an old gas camping stove to head the pad contact surface until black smoke stops burning off (usually about 30 secs). 


If you want to fix the problem permanently see this thread from a few years back, basically an o-ring that needs replacing.
https://singletrackworld.com/forum/topic/leaking-shimano-calipers-possible-solution/

[krezi]

That's exactly it. Thanks. I wonder if removing pads before storing bike and then reinstalling before riding is more time efficient solution.

Did you replace the oring on yours?

Thanks
Pawel

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[krezi]

it's sorted now!

The way to do this as Feed suggested is to blaze the pads over fire, I just used pliers to hold it and it takes only a minute or so per pad. You can see the fumes showing up once they are gone you know pads are clean. Probably best to blaze the pads and not do the sanding. I did sanding before and it didn't remediate the issue. Then I took off the discs and cleaned them with washing liquid and a sponge just rubbing them, Upon installation brakes are good as new.

The whole procedure takes like 10 minutes per wheel so not a big deal but if I had to do it before every ride I would probably give it up! I suppose twice a year after longer break using the bike it's ok to do this! In ideal world there would be no need to do it at all and I heard that sram brakes don't leak but they are so tricky to bleed so you can't win! Shimano are very easy to maintain and bleed the system

Also for new people not familiar with the issue don't let any bike shop tell you that you need new rotors or pads. I heard it before and it's just not true, unless your pads are worn out completely and disc thickness for shimano below 1.5 mm. It's a pity that shimano do not recognise the issue officially and remediate it completely. Even bike shops are reluctant to do this as it is relatively long procedure for very little money and no new parts

Hope this is helpful to somebody

Pawel

[feed]

Did you replace the oring on yours?

I bought the o rings but never replaced. I had one set that were very bad on a hybrid commuter bike I bought from Halfords. They would only last about 4 weeks between cleans, even with regular use. I brought the brakes back and got them replaced. They still get the issue but only if stood up for a while. The newer Shimano brakes on the other bikes don’t have the issue.

[krezi]

I have two bikes one from 2015 and other from 2016 and they both suffer from this issue. Wonder if newer calipers have better design

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[feed]

I have two bikes one from 2015 and other from 2016 and they both suffer from this issue. Wonder if newer calipers have better design

They've definitely resolved the issue they never admitted to having 
I can give you 4 O rings if you want to make the effort to sort it permanently.

[krezi]

I have two bikes one from 2015 and other from 2016 and they both suffer from this issue. Wonder if newer calipers have better design

They've definitely resolved the issue they never admitted to having 
I can give you 4 O rings if you want to make the effort to sort it permanently.

Thanks Dec I might give it a go and try to sort it out permanently. This mystery has been wrecking my head for way too long!

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[feed]

Well the commuter bike  has been hanging on the wall for 2 months, took it down and the brakes were shite. Did the normal, scrubbed the pads,  scrubbed the rotors, but decided it was time to bite the bullet and split the calipers and replace the o ring. Took five mins per caliper, only a few drops of fluid escaped, still required a full bleed after which was about 20mins per end. I love how  simple Shimano brakes are to bleed.  Test run, after a few pulls on the brakes they're good enough to lock up the wheels no problem. Will report back after the bike has been hanging on the wall another 2 months   

[krezi]

Nice one Dec, keep us posted on the o ring solution. I miight go this route too

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[saccades]

I'm still trying to understand the phrase "bike sitting idle".












 

[feed]

2 weeks hanging up, took it down and out for a quick spin. Brakes 100%. Seem to be sorted.

[DerMot]

I am stupid, but did see this post - http://blueliquidlabs.com/repairs/solving-that-brake-squeal/


What o rings do I need and where to get them?
I initially thought it was on the piston, but from the pics shown in the aboce post, it looks like within the caliper.  It does seem to look like that's where my leak is coming from (stain of oil in that area, on two calipers).


Any idea what the size material of these o rings is?  And where to buy them would be great.


EDIT:-
sorry, I am stupid, these are the correct ones?  https://www.ebay.co.uk/itm/141455807147?_trksid=p2060353.m1438.l2649&var=440603744128&ssPageName=STRK:MEBIDX:IT


edit AGAIN:-


I am confused from teh topic quoted at the top, these are the calipers I have (M765). I do need the piston one then I think.


What about if you have a Shimano 1 piece caliper that’s leaking and squealing? That’s definitely happened before. Models I’ve seen this happen to include the M765, M775 and even the M800.

[krezi]

Yeah that's good manual with pics you have there Dermot. I haven't replaced the o ring on my brakes but I know this is the source of losing power if bike sits idle for longer period of time. The leak is so tiny that when you use bike often you might not notice it at all as the fluid is burned once you start braking. I think on newer shimano brakes this is sorted now but I spent months wondering why the bloody brakes lose power and it was so frustrating as you want to go out and realise brakes are not great etc.


Pawel

[feed]

Hey Dermot, that's the correct link

You need to undo the two bolts holding the two halves of the caliper together. Then you'll see a small o ring over the hole where the fluid moves from one half to the other. Replace, bleed, enjoy squeal free effective brakes.