k75s rear brake

[croup101]

i have an issue with my rear brake on my bmw k75s, when i apply it too hard or use it too much it becomes spongy and doesnt work.

do i have dodgy brakes or a bigger problem?

[eastanglianbiker]

have you checked the condition of the brake hose as it could be expanding under use and need replacing

[fredc]

When did you last change the brake fluid

It could be boiling and causing a vapour lock

[Tango]

Have you changed the fluid recently? It is hygroscopic and over time absorbs moisture from the atmosphere. Under heavy use the brakes get hot and the moisture can boil off effectively putting "air" into the system.

Other things could be pistons sticking when they get hot.

I would go for new fluid (if this hasn't been done for a while) then maybe calliper rebuild.

Cheers,

Bob

[croup101]

thanks for the info guys, bought the bike last year so not sure when the fluid was changed might go for that option first. front brake works fine although it does squeek a lot does that make a difference?

[Fozzie]

thanks for the info guys, bought the bike last year so not sure when the fluid was changed might go for that option first. front brake works fine although it does squeek a lot does that make a difference?

 

Most likely just vibration between pad and piston... Copper grease the back of the pad and the problem should be solved