The Very First S-Caliper?, an interesting look at one of DaveP's calipers Options

[Eric_Shea]

Dave Pateman sent some S-Calipers down for a dichromate re-do (not these in the thread, a later pair off a 73+ car) and he graciously sent an odd-ball caliper he had laying around for me to have a look at.

It sure proved interesting and, I have my "theory(s)" as to what it is and how it, and the following S-Caliper lineage came to be. The theory goes like this:

Porsche has been well documented in proving a concept at the track and then positioning that concept on their production line vehicles. I believe that ATE was commissioned to make a lighter caliper for their racing vehicles. I believe what we're about to see is one of the first basic S-Calipers to exist.

On with a tale of two S-Calipers:



Mine's on the left. It's a reconditioned, very early (69-70) S-Caliper that I will be using on my GT car. Dave's one-off is on the right. The first glaringly obvious difference is the endurance pad pin assembly. Any car that is going to go through S-Caliper pads in a single race is probably going at it for 24 hours.



Upon further inspection, this caliper was finish machined slightly different as well. The tops were flattened but only by a small amount. Various logos and markings are not in the usual production locations and there's a few "niceties" that would be missing. I'll try to cover it all herein.

First let's look at the bottom side logos. Both are "basically" in the same place but, the casting lines from the production caliper (red arrow) is missing and the logo is centered (refinishers buffed the other logo a tad much):




The flute around the pad cavity is slightly different. These calipers are nearly identical with the exception of some of these things which lead me to believe a later production model was molded off the same casting. The later flute is slightly deeper:




Again, markings and castings are slightly different. I do not believe the 68 represents a year. Mine have similar markings elsewhere on the caliper and they're something like 33. I would guess a finisher stamp??




Here's one of the convenience things or "niceties" I found. It's a pain in the @$$ to get S-Caliper lines and bleeders off. These must have been a bear. Note how the later production model caliper differs:




This stamping on the machined top tells me this was no afterthought to make it fit a certain wheel. The race dept. probably worked closely with ATE for these specs.:



Here's the two side by side. Again, proportionately these calipers are identical. You can see how they finished the top on this caliper:



On the side of the nose of the caliper there's an odd bump, possibly denoting the back of the piston chamber. The production model bump is more pronounced:




Here's a little more detail on the quick-change endurance pad pin. While this was a rather crude adaptation to the original caliper, I do believe it falls right in line with a factory race look and feel. I'm fairly certain this was an original mod.:






Pistons are different. The one-off has a very deep piston top. The standard S-Caliper piston is pictured in-hand:




The pin assembly itself is rather crude and not even but again I think this is a factory manifestation. I've seen these pins on one other set of calipers but without the latch mechanism. All in all, it was an interesting afternoon (for me anyway). Here's a full-on shot of both calipers (pay no attention to the two pair of original GT calipers in the background!):




What are your thoughts?

[davep]

A. Serrano has extensive documentation of the 908 caliper on his website:
http://www.pbase.com/9146gt/gt_alloy_calipers

Note the photo purporting to show the 908 caliper on the 907?
Since I don't see the release pin on the top of the caliper, and see a dark shape on the side, I wonder if it shows the 910 caliper instead? They are very closely related.

Jeff, your photos do show the 910 caliper and a 908 caliper. My caliper appears to be somewhere in between. In fact there may be two 910 calipers or even three. The first would be one with the round rear cover, and the regular pins. The second would be the one shown in the 910 manual with the round rear cover and the quick release U-pin. Perhaps mine is the third variety with the four bolt rear plate, and the U-pin. My caliper does not have the Knock-back pins in the caliper as does the 908 caliper.