Piston retaining plate

Lahti411 · Post by **Lahti411** » Tue Nov 11, 2008 11:40 am

I changed the seals for my '72 411's brake callipers and noticed that my callipers didn't have the piston retaining plates. I have couple of pairs of callipers and none of them had the piston retaining plates. How necessary are these? Are these available or did any other car use the same plates?

Lars S · Post by **Lars S** » Tue Nov 11, 2008 12:14 pm

From what I know the retaining plate makes the piston stay in the same angle (not rotate) so that the cut out in the flange of the piston is about 20 degrees. This should allow the pad to tilt a small bit when breaking and reduce the risk for squeal/noise.
I do not believe it is unique to leave them out.

Lars S

Wally · Post by **Wally** » Tue Nov 11, 2008 12:33 pm

Late type 3 calipers are the same. Maybe look for those? Early 914 may fit as well.

Lahti411 · Post by **Lahti411** » Tue Nov 11, 2008 12:57 pm

Yeah, I know it's the same calliper, but as I already have several callipers I wouldn't want to buy an extra pair... I have seen calliper repair kits for sale, which include all the wearing parts, but not for a while though. But if anyone (in the EU) have an extra pair of these plates, please contact.

raygreenwood · Post by **raygreenwood** » Wed Nov 12, 2008 12:49 pm

Yes, they are anti-rotation plates primarily. The type 3's will fit, but sometimes need to have the prongs in the center adjusted. You really can just make some with .015" to .020" sheet metal, a scriber and tin snips.
Some technical literature desiribes one of the functions of these as anti-rattle plates. That is not correct. The anti-rattle plates are actually the spring assembly between teh pins aginast the back of the pads.

The object of not having the pistons rotatee is to keep from leakingfluid and wearing the seals.
By the way, early type 3 calipers are not the same. Its late type 3 is the same as early 411. After that you have different calipers, steering knuckles and rotors. Ray

412s2 · Post by **412s2** » Wed Nov 12, 2008 1:38 pm

I've noticed a lot of the pads you get for new cars have a kind of glue on the back of the pad that the piston sticks to. My Porsche has metal spring cups that fit inside the pistons, attached to these cups are a sticky rubber pad which sticks to the back of the friction pad. They call is a dampening disc. Click here to see. I guess these systems also actively pull the pad away from the disc when the piston retracts as well as helping to prevent the piston from turning in the cylinder??

Could this system be used in the 411/412?

raygreenwood · Post by **raygreenwood** » Wed Nov 12, 2008 2:27 pm

What they really do the most of....is to keep the pad from trying to rotate. There is a small amount of slack in the pins and eyse that hold the pads in place....and also on the channels of modern sliding calipers....where the prongs on the pads fit in. The rotating disk tries to coks the pad that is cantilevered across it......causing chatter.
It is this pad chatter that causes "squeeling" because.... the angle of the pad to the surface of the rotor...which has minute grooves...or surface "knap"....changes during this chattering.....causing squeeling. The object of resiliant pads or adhesives on the back of pads is to give the contact between pad and piston...traction....to prevent the pad chatter.

There is a nice set of compress able aluminum shims with high temp adhesive available from Raybestos for 914/412 pads. The slightly deform against the face of teh piston...impressing the shape of the piston into the .020-.025" shim....so that the pad cannot change angle when it vibrates.....so it rattles and squeels less if at all. Ray