Brake problems

13ADL1X

Hello,

I've got a Hope Mono Mini rear brake.
Recently I've noticed that when pulling the lever it sounds like air is being forced out from where the lever piston goes into the master cylinder. The brake also whilst the pads move doesn't really do anything.

Has anyone else had this issue? Was it a case of bleeding the system or replacing the seals on the lever?

artillerydave

any problems like this the first stage to repair is really a strip down and re bleed then see how things go. you might have had a small leak or lost a bit of fluid and the brakes are not performing. if you are in doubt about bleeding I would visit your bikeshop but it is an easy diy job.

13ADL1X

I'm fine with bleeding so I've bled it this morning there's a little improvement but the noise is still there. This has happened before where it gets bled and then having sat around for a while I go for a ride to find its not working again.

So I've just ordered a lever seal kit and gonna strip it down and try to make it all new again. I've not done a rebuild before though. Do you completely empty the Master Cylinder of fluid?

This could be a great opportunity to fit the Goodridge Hose kit I got about a year ago! Hooray. In fact the temptation to buy a new floating rotor disc is becoming to much to bear. Don't tell the wife!

skyliner

The problem you're experiencing is probably due to the MC cap bolts being overtightened at some point. If you remove the the MC cap and run your finger over the bolt holes in the lever body on top of the MC res, you'll feel the raised sections of thread that have been pulled up when the bolts were overtightened. (the brake sounds like it's spitting when you pull the lever, and if you look at the breather hole on the cap, it is doing just that.)
To fix it, you need to chamfer the edges of the bolt holes with a 5mm HSS drill bit BY HAND i.e. holding the drill bit between your fingers and removing the raised bit of alloy to allow the diaphragm to sit flush on the MC res and seal properly.

tjm

if you do that be VERY careful you don't get swarf in the reservoir.

13ADL1X

I'll check that tonight just to make sure. However, it isn't spitting and there is no sign of fluid, bubbles or air coming out the breather hole.

13ADL1X

Right, took MC cap off and threads felt fine. Did the drill thing gently anyway put it back together and the problem is still there. As per my last post there is nothing spitting and no leaks from the breather hole.

Replacement seal kit arrived yesterday so am just gonna drain the fluid right down, strip the lever, fit my new hose and pads and hopefully it will be back to normal.