Hot brakes binding

mb4807 · Oct 21, 2012

I use a Beta Rev 3 for technical trail riding in the alps. On longer descents , no matter how brake-friendly I ride (low gear, really slow, as much engine braking as I can find) the brakes get really hot and start to bind on.

Anyone got any ideas on what I can do to improve the situation. I am using good quality Galfer pads, but was wondering if I could use dot 5.1 fluid perhaps or find other ways to dissipate heat better?

AberdeenAngus · Oct 21, 2012

I think any of the brake fluids specifically designed for racing (eg Castrol SRF)would help you as they have a much higher boiling point than normal fluid.

Myke Rocks · Oct 21, 2012

simple really

mb4807 said:
I use a Beta Rev 3 for technical trail riding in the alps. On longer descents , no matter how brake-friendly I ride (low gear, really slow, as much engine braking as I can find) the brakes get really hot and start to bind on.

Anyone got any ideas on what I can do to improve the situation. I am using good quality Galfer pads, but was wondering if I could use dot 5.1 fluid perhaps or find other ways to dissipate heat better?

Nothing to do with brake fluid type.
There is a lack of clearance on the master cylinder concerned when the brake lever is released. The master cylinder piston is being kept slightly compressed. In this state, the vent back to the reservoir is sealed, and, when brakes are cold you do not notice it. When the brake fluid heats up, the expansion brings the brakes on because the expansion path back to the reservoir is blocked.
Myke

mb4807 · Oct 23, 2012

Can I fix it

Myke Rocks said:
Nothing to do with brake fluid type.
There is a lack of clearance on the master cylinder concerned when the brake lever is released. The master cylinder piston is being kept slightly compressed. In this state, the vent back to the reservoir is sealed, and, when brakes are cold you do not notice it. When the brake fluid heats up, the expansion brings the brakes on because the expansion path back to the reservoir is blocked.
Myke

Thanks for that. Is that something I can do something about, or is it just the design of the master cylinder?

Myke Rocks · Oct 23, 2012

Not knowing the actual design:

mb4807 said:
Thanks for that. Is that something I can do something about, or is it just the design of the master cylinder?

I cannot say what the probem is.
It is unlikely to be a design fault in the master cylinder, much more likely that ( if a front brake) the lever has been broken and replaced with an incorrect model, which keeps the cylinder slightly depressed, or in the case of the rear brake, a rear brake lever stop has been adjusted downwards slightly or lever bent in knock so that the same thing happens.
Myke

Timpo · Oct 23, 2012

Didn't the standard lever have a adjustable plunge screw, this is what acts on to the cylinder spool when lever is pulled.
If there is a screw, loosen the locknut and back the screw off until there is some free play between the screw and spool.
You can see what I mean on this pic:-

Also, ensure you have the correct amount of fluid in, not too much. And also check that the vent hole in the reservoir cap is not blocked.

Hot brakes binding

mb4807

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AberdeenAngus

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Myke Rocks

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mb4807

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Myke Rocks

Well-known member

Timpo

North Wales TRF

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