The two bleeders Options

[emerygt350]

I just popped on my newly remastered rear brake calipers from PMB and was wondering if there was a point to the lower bleeder? I only ever bothered with the top bleeder before but now that it's bone dry I was wondering if that might be why the second bleeder exists? I will be bleeding the brakes tomorrow morning.

[davep]

Dual bleed nipples of the 914 rear have nothing to do with handedness, the parking brake lever defines that.
However, I have found that when doing an annual fluid bleed it is often better to open both bleed nipples to fully drain the calipers before refilling. Forty years ago I had to start rebuilding the calipers to keep them fully functional; there was no PMB to send calipers to and there were no (!) parts available in any case. Taking the pistons out was a real eye opener since the outer pistons were always filled with more crap than the inners. The reason for this is simple. The fluid inlet is on the inner side of the caliper as are the bleed nipples. When you do a quick flush and bleed the fluid enters the inlet and heads straight for the open nipple. This does not flush the fluid inside the pistons, particularly the 914 rears with the adjuster mechanism inside, and it certainly does not do much of a job in circulating to the outer half of the caliper. The result is that old fluid is retained inside the pistons and most of the outer caliper half with a quick flush and bleed. Hence my method was to drain the calipers first, then do a complete refill and bleed. Every few years I would disassemble the calipers to thoroughly clean inside to keep them operating efficiently.

[Superhawk996]

Dual bleed nipples of the 914 rear have nothing to do with handedness, the parking brake lever defines that.

Disagree. You have to look at this from a manufacturing perspective.

Take a look at the inboard side casting, it is symmetric. The casting is not handed until the machining operations are done for the handbrake.

Having lived and worked in a manufacturing environment, my best educated guess is that the piston bore and the bleed screws were machined before the park brake bore.

This allows the casting to remain unhanded for easier inventory management. Since ATE was suppling these calipers to other OEMs there would be an advantage to not having handed calipers until as late in the machining process as possible.

In this day and age, no one would do two matching operations and provide two bleed screws. It amounts to giving away money. But back in the 70s before computer inventory management and just in time delivery of parts there would be a great deal of value in minimizing handed parts.