Re: Treadle Lightly

Posted by Ross On 2013/9/23 5:53:01

Nicely done. A few observations: The failure mode that everyone is concerned about is of the hydraulic portion. I fully agree that the vacuum side needs to be rebuilt and do so on the units that pass through here.

I don't fret much about pits in the vacuum cylinder unless they cover a wide area in the working zone. It operates at the equivalent of maybe 7 psi during a panic stop, and the wiping area of the leather seal is quite wide. Even if the vac side were to fail utterly you can still stop the car though it is not fun.

The style of check valve doesn't seem much of an issue as long as it maintains the the residual pressure that drum brake cylinders prefer. The internals of the master cylinder don't see that residual pressure in any event.

The important failures are hydraulic ones and that is addressed by a careful workmanlike rebuild of that portion, as you noted. I am quite anal about having a perfectly smooth hydraulic piston and carefully seating the seals in their bore. That, and being careful with the installation of the compensator valve.

Look forward to the results of your test.