Hydraulic brake problem

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Thehairs1970
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Joined: 11 Aug 2018, 9:30am

Hydraulic brake problem

Post by Thehairs1970 »

My wife’s tourer has Shimano Hydraulic brakes which work well most of the time. However, if comes down a steep hill with them on a lot (she’s not brave), they bind for a while once at the bottom. They can be pushed back and even seem to unbind themselves slowly. Any ideas?
Marcus Aurelius
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Joined: 1 Feb 2018, 10:20am

Re: Hydraulic brake problem

Post by Marcus Aurelius »

It sounds like they’re being allowed to over heat by not being modulated effectively enough. If they’re being pushed, by steep descents / fast riding, I’d hazard a guess that the modulation technique needs to be refined a bit.
Thehairs1970
Posts: 604
Joined: 11 Aug 2018, 9:30am

Re: Hydraulic brake problem

Post by Thehairs1970 »

Mmm. I’ve never had that problem myself, even while using brakes heavily.
Thehairs1970
Posts: 604
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Re: Hydraulic brake problem

Post by Thehairs1970 »

Should probably that these are normal descents, not very fast and no load. Only seems to be a recent thing too.
Jupestar
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Joined: 29 Feb 2020, 3:03pm

Re: Hydraulic brake problem

Post by Jupestar »

Sounds like heating and cooling of the mineral oil to me. Depends on what type of system you have, what you can try. But if this is a new problem, then a bleed to get any air out would help.
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andrew_s
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Re: Hydraulic brake problem

Post by andrew_s »

What model of brake?

If they are a closed system, the hydraulic fluid can expand with the heat from the brake, pushing the brake on.
It can also happen with open systems if you don't fully release the brake lever to open the reservoir port.

The continuous braking of a timid rider on a steep hill is just about the worst thing you can do for generating heat.
Intermittent plummet and stop braking gives fewer problems - not only do the brakes get a chance to cool during the plummet phase, air resistance does a lot of the braking for you, so there's less total heat going in to the brakes.

One thing that can help with a timid rider is alternating use of the front and rear brakes, which gives the cooling periods, if not the air braking.

Air in the system, or water in the brake fluid, can cause loss of braking.
Thehairs1970
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Re: Hydraulic brake problem

Post by Thehairs1970 »

The brakes are Shimano MT200.
gregoryoftours
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Re: Hydraulic brake problem

Post by gregoryoftours »

andrew_s wrote: 17 Apr 2021, 9:02pm It can also happen with open systems if you don't fully release the brake lever to open the reservoir port.
The continuous braking of a timid rider on a steep hill is just about the worst thing you can do for generating heat.
This seems most likely to me.
Thehairs1970
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Joined: 11 Aug 2018, 9:30am

Re: Hydraulic brake problem

Post by Thehairs1970 »

Thanks for replies.
Thehairs1970
Posts: 604
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Re: Hydraulic brake problem

Post by Thehairs1970 »

Update.

Had the brakes bled and rotors cleaned. Problem is still there. I decided to try the bike myself and got the problem too. Not a lot of braking. 25m of dragging the brakes followed by pulling to a stop made the brakes rub enough that the wheel was reluctant to turn. I’ve been using hydraulic brakes for years and never had this problem. Anything else I could try.
wirral_cyclist
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Re: Hydraulic brake problem

Post by wirral_cyclist »

Is the caliper centred on the rotor? If not then the braking can be poor and generate a bit of extra heat from nearest pad rubbing first before furthest pad starts clamping.
PH
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Re: Hydraulic brake problem

Post by PH »

If you haven't already, try cleaning the seals as it could be sticking pistons
https://www.youtube.com/watch?v=vQXFFgRButo
Thehairs1970
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Joined: 11 Aug 2018, 9:30am

Re: Hydraulic brake problem

Post by Thehairs1970 »

wirral_cyclist wrote: 29 May 2021, 1:08pm Is the caliper centred on the rotor? If not then the braking can be poor and generate a bit of extra heat from nearest pad rubbing first before furthest pad starts clamping.
I realigned them too.
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fausto99
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Location: NW Kent

Re: Hydraulic brake problem

Post by fausto99 »

PH wrote: 29 May 2021, 1:33pm If you haven't already, try cleaning the seals as it could be sticking pistons
https://www.youtube.com/watch?v=vQXFFgRButo
Great video. I don't have any bikes with hydraulic brakes, but if I ever do, now I know. :D
Thehairs1970
Posts: 604
Joined: 11 Aug 2018, 9:30am

Re: Hydraulic brake problem

Post by Thehairs1970 »

I’ll give the seal clean a go.
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