Vintage 911S Caliper Restoration Thread

[Dmill]

echoing others...Eric really great article in Essses.

[Neunelfer]

Thanks gang! Giving back for all of the great info and friends I've gotten via the earlysreg. Thank "you".

Bob, 100 is best and yes, that's really the main point of the article. When rebuilding a caliper, the plating on the inside of the bore is as much or... no, simply "moreso" important than the plating on the outside. Here's the immutable basics behind that statement:

1. Brake fluid is "hygroscopic". It will absorb water.
2. Your hydraulic system is open. Look for the little pin holes in the cap on your reservoir. Water will enter through the atmosphere. It also comes in through torn dust boots.
3. Water likes to gather around the rubber seals.
4. Your Pistons "will" eventually wear this plating off the bores (we are seeing an enormous influx of SC's and Carrera cars right now if that tells you anything) the wear pattern is just below the rubber bore seal.
5. If left sitting, your calipers will begin to rust from the inside out. This is when they begin to bind. The torn dust boot causes rust just above the rubber bore seal. The sitting caliper will rust below the bore seal.

This is a common question because people think that bore is a real "precision fit". Others have preyed off this in the past (ever hear of a totally useless, snake oil pitch on "stainless steel sleeves"?). The seal itself is the sealing surface, the bore is simply there to stabilize the piston in its travel. I've "never" seen a caliper that needs to be re-sleeved. I have seen machine shops that have overhead and bills to pay however.

So, yes, plate them inside and out with "zinc" and a yellow dichromate bath. Here comes a plug for the DIY crowd; we plate caliper bodies for $60.00 per pair and fasteners to black zinc for $2.00 each. USPS Priority Mail Flat Rate boxes are tailor made for this type of shipment.

If you have alloy calipers on your 911S, the exact same principle applies. Simply replace the words plating and zinc for anodizing. Pistons will wear the anodizing off the "top" of your bore. When we restore those calipers we re-anodize the entire body and flip them (swapping left for right)

I hope that helps.

Thanks again gang. See you in LA/Anaheim (or Hershey)

[javadog]

Eric,

What brand of brake grease do you use?

Thanks,
JR

[Neunelfer]

Hi JR,

For the bulk of our work we use for Permatex ceramic lubricant. It does not harm the rubber seals.

We also have a large tube of the ATE assembly paste.

[lkadams]

Eric,

I wanted to pass on my thanks for your article in the Esses. I have a 1969 MB 280SE coupe that has caliper problems (seized pistons, I believe) and I was thinking the best bet would be to take them all off and send them in. However the great info you provided gives me hope that I can get the pistons moving again - before taking them off and sending them in

[Neunelfer]

I'll save you the effort. It's the same price regardless...

[lkadams]

I'll save you the effort. It's the same price regardless...

Duly noted!

[BOYER73S]

Hi Eric

Those calipers I emailed you about are off the car (69S) but they seem to have a date of 4/78 on them but I have read this post and you mention the calipers are not dates so must be some other number

How do I tell if they are 69 alloy brakes for sure, car was built 2/69

Thanks

[Fishcop]

Clyde, this post from Eric may help you... http://www.early911sregistry.org/for...hlight=caliper

[BOYER73S]

Good one John I searched Early S last night but didn't find that thread

So here are 2 pics of what I have look like 69-70 ones to me based on Erics pics but I am puzzled by the stamping on both calipers 24 in a box and 478 which I took to mean 4/78 but perhaps not

The colour is definately a grey not green so maybe all the ducks have lined up.

What do you think?