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?

[Eric_Shea]

Eric comes up with another brain bomb.

That would be a first... I'm fairly certain Jeff dropped the brain bomb here. (IMG:style_emoticons/default/wink.gif)

Here's what I'm pulling out of this data and pictures:

Not 910 - Those are Jeff's calipers on the blue background and Dave's calipers on the wood flooring. HOWEVER, Dave's photo from the manual does show this quick change mechanism on the 910 caliper (note the rounded hump in the back of the caliper on the top picture)

These pre-date Jeff's 908 picture? - The calipers on the green background; I'm going to guess at this as I feel the quick change mechanism on this is an adaptation to the basic casting and, I feel the quick change mechanism in Jeff's photo would be faster and better. What's not shown there is the bottom of those calipers where they have pad plates (no need for pins) for the pads to rest on. Changing was as easy as pulling the knob, yanking the pads, replacing and snapping the spring back into place. This method became the norm on later Brembos (944T as an example uses a spring assembly that could possibly trace it's roots back to this caliper.)

Again, notice Jeff's green 908 picture and you'll see the compensating line and bleeder cutouts are still missing as well.

Jeff, I wondered about the shaving of the top for clearance as well, it seems like that's the answer. This would mean that "all" of these calipers were probably one off's with the race dept. working closely with ATE.

The one thing that amazes me is... these are S-Calipers. The basic casting is identical. Oh, there are differences that can be seen for sure but, pound for pound, this is an S-Caliper.

I would still place this as one of the first in the 908 S-Caliper vein. Mainly because of the quick change endurance pin set. I'm guessing what Dave has pre-dates the one's in Jeff's picture. That's what has been puzzling about this caliper all along. It doesn't look like the standard 908 or (obviously) the 910.

Jump in gang! Fun stuff. Thanks Jeff (IMG:style_emoticons/default/smilie_pokal.gif)