The Mystical Self-Adjusting Brake Lever

Hey all!

So I'm riding my Seca around, and I've noticed that as it gets warmer (i.e., 55, 60, 70 degrees instead of 20, 30, 40) that the brake lever seems to adjust itself.

Specifically, when I go to start her up in the morning, the brake lever seems loose - there's too much slack in it, both by feel and as indicated on the lever itself.

So I spin the little adjuster wheel, set the slack properly, and off I go to work. I get to work, everything feels fine, and I park the bike.

I come back eight hours later, and the lever has become significantly tighter - to the point where there's sometimes little or no slack whatsoever. So I adjust the lever and ride home, and park the Seca in the garage...

...where, when it's chilly out again the next morning, the lever will have regained its excess slack.

Thoughts, comments, considerations, questions?

 

You've got air and/or moisture in the system.

When it gets hot, it expands. Contracts when it cools down.

Air, or just really old brake fluid, with lots of moisture absorbed into it.

Have you rebuilt those brakes yet? New lines, pads, caliper and master cylinder seals, etc? And of course, fresh fluid?

If not, you need to be. If yes, then you just need to bleed them again.

 

Yes to all of the above. More bleeding for me then, I guess.

 

IF, ... you have Bled he system correctly and there's Clean Fluid throughout ...

The Brake Lever gaining and losing efficiency is an early indicator that the Pressure Seal is beginning to fail.

Using the Brakes "Pumps-up" the System and the Pressure INCREASES causing the Lever to react to the Increased Pressure.

Overnight, ... the Pressure seeps beyond the Pressure Seal and the little-bit of Fluid that causes the differential returns to the Reservoir.

> Check the Brake Pads. This is one symptom that the Pads are close too or beyond the limit.

> Look in the Reservoir. If the Level is low and the Diaphragm Rubber Gasket is expanded, ... there is insufficient Fluid ... Worn Pads --or-- Both.

 

He rebuilt the brakes Rick.

Yep. Like I said, it shouldn't take much.

 

Hook-up a Clear length of Hose to a Bleeder.

Bleed the Brakes in the Conventional Manner where the Brake Lever is Pumped-up until Hydraulic Pressure is achieved and OPEN the Bleeder squeezing-out the Fluid as the Bbrake Lever is Held Fast to the Handlebar.

After 2 -or- 3 repetitions the Hose should be filled with Fluid.
Let some Fluid out from the end so that you can observe the Level of Fluid in the Hose.

Leave the Bleeder OPEN and PUMP the Brake Lever.
Fluid should get pumped.
When the Brake Lever is Squeezed and Released, ... the MC should PUMP Fluid out.

If the Brake Fluid just moves "Back and forth" with NO significant movement toward getting Pumped, ...

The REAR Seal is Pushing and Pulling Fluid.
The INBOARD Seal is compromized in some manner,
a) Ill fitting
b) Incorrect Part
c) Incorrectly placed
d) Debris on MC Bore
e) Severe Pitting of the MC Bore