[meinenotyours]

I recently (last month) replaced my front brake rotor and upgraded my brake line to braided steel. I had rebuilt the caliper and replaced both pistons in March or April of this year. Everything seemed great, brakes were preforming better, definitely less "spongy."

On my last ride, I noticed that the front lever feels as though there's less play, and that the brake feels like it isn't engaging fully until the lever is squeezed in excessively hard. There's a significant loss in braking power. I rode it around the block to test things out, and the rotor was warm to the touch from friction from going just a few hundred yards.

The master cylinder hasn't been cleaned/rebuilt in about 2 years - the bike has seen about 6k miles in that time. I'm not really sure what the symptoms of a master cylinder that needs rebuilding are - I've had it done once previously when the brakes were sticking so badly the bike was almost impossible to roll.

The caliper definitely disengages - the bike rolls perfectly fine. It's more an issue of it being all or nothing - there's no transition or easing on the brake. Does this sound like anything anyone has experienced before? I'm curious if it could be the master cylinder because I've replaced or rebuilt every other component recently, and so I'm doubtful that the brake line/caliper/pistons/pads/rotor are the culprit. Any thoughts, anecdotes, or advice would be greatly appreciated!

 

[dtsmjr8dan]

Make sure the holes in the bottom of your mc reservoir are clear. It sounds like the front one is plugged. A really thin wire will clear it. The hole is in the center of a divot and sometimes hard to see.

 

[longdistancerider]

+1 for the pressure relief port being plugged.

 

[meinenotyours]

Thanks for the tips. Turns out the brake light pressure switch banjo bolt I put in to reconnect my MC to my brake light was a piece of garbage. It was leaking brake fluid, and the circuit was broken. I took that out and replaced with a standard banjo, repositioned the brake lever on my bars so it had no clearance issues with the MC, polished and lubed the lever itself at the connecting bolt, and the problem was solved. With the lever off, the piston seemed to be rebounding when I poked at it by the MC without any problem, so I didn't go the whole 9 of taking the MC apart. A quick brake bleed later and I was good to go.