914 Brake Caliper info, Whats the internal pin for? They stick Options

[Thorshammer]

Okay,


So I am rebuilding a set of calipers of a customers 914 FP racecar.

One front is a standard "M" caliper with 3 inch spacing and a center pin internal of the piston. This pin sticks out from the center of the caliper piston bore and the piston center has a rubber seal and the pin sticks into the piston.

Anyone know what this pin is for????

I also have another front caliper which has no center pin and the caliper piston is not cupped on the fluid side, so the second caliper has less fluid in it. I found a caliper in the customers spares kit which had a 411 XXX XXX part number on it. From my VW days I deduced this is probably a 411 VW caliper. Same piston diameter and 3.0 inch bolt spacing.

The rears are standard early front calipers from a 914-4.

Here are the questions:

What calipers will bolt onto a 3.0 inch bolt spacing that are two piston calipers??? for the front.

What calipers are the same bolt spacing as 914 front calipers, and are the same piston size?

Observations:

When rebuilding the standard 914 calipers (with the center pin) the caliper pistons move really hard, even with use, or new with Brembo caliper grease.

The "411" caliper pistons move very easily, and I mean this is a big difference. They also retract better, when on the car, you can actually turn the wheel much better than the other calipers.

I am at a loss for whether a piston design that has a cup on the fluid side (more fluid volume) will be better for heat dissapation, or if a piston design that has an almost flat back side (fluid side) will (less fluid) work better. Does anyone make a ceramic insert so the pads will not transfer heat to the pistons to the fluid as easily.

Obviously I am looking for a performance improvement, In two ways:

One piston retracts much better than the other, so less rolling resistance

One piston design that will keep the brakes cooler

This is my dilema.

Erik Madsen