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?

[Jeff Hail]

What are your thoughts?

I know exactly what they came from and what the markings mean.

Those are calipers that were used on the 908 race car. On rare instances they could be found on the factory late 904, 914-6GT and 911ST race cars as an upgrade to the stock brakes.

The quick change Uni-pin is the give away that they are race parts normally found on endurance racers where fast pit time were just as important as a fast lap.

Other hints that they came from somewhere betwen 904-908 series is the machined "head" allowing more clearance for a smaller wheel. Some 904-908 hill climb cars used diminutive 13 inch wheels as the front bodywork was lowered to provide improved areodynamics and reduced frontal area. The caliper head would have to be machined to allow clearance for a smaller wheel.

The "V" stamping indicates a very early caliper possibly as early as the 904 model. The "V" stamp was a designation for Ollon-Villar cars which were used in hill climbs and carried over into the 908, 911ST and 914-6GT models as an option.
The numerical stamp was a batch value not a year of production.

Adding a twist those are 910-907 pistons. Porsche learned the leading edge of the pads would wear faster than the trailing edge in racing. A redesign of the piston was made from earlier models and this would carry all the way over to into the 917 caliper pistons from lessons learned. The deep piston also helped with heat keeping the heat from transfering from the pad to the caliper body preventing fluid boil. The pistons were machined with an ever so slight cant to allow for even wear front to rear along with a deeper cut in the dish area. I bet if you mic the pistons you will see a 2 thousands difference where the front and rear of the pads meet the face.



Here is a sample of the 908 Quick Change calipers with shaved heads and the later 910-07s with updated pistons. The physical differences are clear in the photos.

Eric you have a great eye for noticing the differences that you found. That sample is worth its weight in gold. Proving again you are the Master.

[914Sixer]

Porsche was always making upgrades and small changes. Thank you for showing the small differences. Most of us would never get a chance to see 907,908 calipers with the quick change application.

[URY914]

Eric,

I got a whole box of those calipers. I bought them at a yard sale about three years ago.










OK, not really.

[davep]

I have had this caliper for about 20 years, and knew from the start that it was something special. It was acquired from a driver that had a 914/6 GT (9140430033) and had raced other Porsche cars. Part of the deal also included titanium con-rod bolts. I was never able to determine the exact use of this caliper though.

The 908 caliper was wider internally for thicker pads, and the quick release mechanism was totally different. It also used shorter pistons, and I believe still used the knock-back mechanism.

Bernie Buschen provided me with this page from the 910 Driver's Manual:


Note that the text says Dunlop disc brake system, they could also be known as Girling calipers. The quick release is identical to my caliper.

Here are some photos of the 910 caliper I found. Perhaps this might be an earlier version since the back cover is completely different:

[davep]

More photos show that this is an ATE caliper and the back end looks to be the same a pictured in the 910 manual:

and

[So.Cal.914]

Just when you think that there is no way to shut-up those that are convinced they

know it all, Eric comes up with another brain bomb. Great info that could come in

handy at a porsche swapmeet. Thanks. (IMG:style_emoticons/default/smile.gif)

[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)

[ericread]

Damn, I get such an education from reading these posts! (IMG:style_emoticons/default/pray.gif) While this information will probably never directly impact me or my 914, knowing the history of these cars makes them even more fun to drive.

I guess the next time I'm at a cocktail party being really bored, I can bring up the Eric Shea S-Caliper 914 brake story! On second thought, probably not the right audience for this story...

Which brings up a question; Do you notice the more you know about your teener, the fewer people you have to talk to about this information? Do you notice the "deer in the headlights" look from people around you when you bring up incredibly interesting, fascinating, and exciting 914 historical parts discussions?

Maybe it's just me...

(IMG:style_emoticons/default/smile.gif)

[Eric_Shea]

Do you notice the "deer in the headlights" look from people around you when you bring up incredibly interesting, fascinating, and exciting 914 historical parts discussions?

Naaaaaa... you just need to show up at WCR and drink beer in the parking lot. You're at the wrong parties! Cocktail to these guys is gasoline with the Techtron additives (maybe a little brake cleaner for a night cap!) (IMG:style_emoticons/default/biggrin.gif)

[ericread]

Do you notice the "deer in the headlights" look from people around you when you bring up incredibly interesting, fascinating, and exciting 914 historical parts discussions?

Naaaaaa... you just need to show up at WCR and drink beer in the parking lot. You're at the wrong parties! Cocktail to these guys is gasoline with the Techtron additives (maybe a little brake cleaner for a night cap!) (IMG:style_emoticons/default/biggrin.gif)

(IMG:style_emoticons/default/lol3.gif)

Seriously Eric, great information! Thanks for sharing this! (IMG:style_emoticons/default/pray.gif)

[Eric_Shea]

Thanks E.

One more measurement from this AM:

There was 3mm (1/8th of an inch) shaved in radius off the tops. (IMG:style_emoticons/default/wink.gif)

[PeeGreen 914]

Do you notice the "deer in the headlights" look from people around you when you bring up incredibly interesting, fascinating, and exciting 914 historical parts discussions?

Naaaaaa... you just need to show up at WCR and drink beer in the parking lot. You're at the wrong parties! Cocktail to these guys is gasoline with the Techtron additives (maybe a little brake cleaner for a night cap!) (IMG:style_emoticons/default/biggrin.gif)

(IMG:style_emoticons/default/piratenanner.gif) Can't wait for the WCR


Seriously Eric, Very nice write up. Thanks for the information and pictures.

[ConeDodger]

Seriously interesting stuff...

I am amazed at what people have laying around. I have a freind back in Minneapolis who has been buying up "crap" for the last 30 years. Mostly Porsche, Datsun, and Mini. I wonder what he has in his boxes... Last I talked to him he had just bought the entire fleet of Mini Mokes off of Catalina Island. I am sure he has some interesting Porsche parts among his stash. I am going to give him a call today...

Eric, Jeff, your knowledge of Porsche history and brakes enriches us all...

[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.

[Jeff Hail]

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.

Without part numbers it is open to some speculation They are clearly some type of an S variant. The stamps hint at what they are .The pics I posted were from Edmond Harris - pretty much the authority of id'ing old Porsche racing parts. Gunnar Racing has two 904's that were restored and one had steel calipers and the other aluminum S binders.

I looked at Armando's site and saw the same thing you did.

One thing I do know is the later 907 and 910's eventually had 6 pot calipers which were carried over to the 917. These were all ATE. The later Salzburg Works 2 and Wyer cars had Girlings. Totally different calipers.

Porsche had some legal woes also with patents stemming from WWII. It had to do with what tires they left the "Works Dept 1 or Salzburg-Works 2" with and what calipers were allowed to be fitted due to the patent issue. This did not include the road cars sold to the public. I will save this chapter for another thread.

[Root_Werks]

Were's that jaw-drop smiley? (IMG:style_emoticons/default/drooley.gif)

[davep]

Jeff, I think we need to talk some more. It is difficult to track exactly what calipers were used on the race cars. I believe that the 904 used calipers that were essentially the same as the 1967 911S; cast iron with bridge lines. I'm not sure what was done to accommodate the 'S' caliper since they used the wider mount spacing. I'm sure this was a conversion done years after the car was delivered.

I'm pretty sure the 917 introduced the use of 4 piston calipers, some were Girling, some were ATE. The ATE calipers morphed into the 4 piston RSR calipers. Bridge widths varied according to rotor thickness and pad thickness. Endurance calipers were wider to permit the thicker pads and rotors.

[ConeDodger]

So these brakes were at home on these cars???

[Eric_Shea]

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.

I would say, unequivocally, that this is not a 910 caliper. It looks to me like the very first 908 caliper which is basically an S-Caliper with a few features as laid out above. I'm going to do a little more posting and searching for answers but to me; this would fall into the 908 caliper with that quick change mechanism shown on the 910 caliper. I'd be willing to bet it would come back as a very early 908 caliper. The fact that these were commonly used on the 914-6/GT and you got it from a friend who had 9140430033... almost seals the deal but, you never know about these things. I'd also be willing to bet the more common 908 caliper (S-Caliper) basically evolved from this with a faster and easier quick change mechanism... making this an even rarer find. No leads on it's partner?

The pair of original rear GT calipers shown in the background came from a GT that underwent a brake upgrade. Many GT's were still tracking when the 930 calipers hit the market, think about how people today go hunting for the latest Boxster/Big Red infusion. Back then, it was the same. Many of these old S-Caliper variants were probably viewed as useless, shop shelf items. Those rears sat on a shelf that long... I'll bet these front calipers probably met the same fate.

I believe that the 904 used calipers that were essentially the same as the 1967 911S; cast iron with bridge lines. I'm not sure what was done to accommodate the 'S' caliper since they used the wider mount spacing. I'm sure this was a conversion done years after the car was delivered.

The 67 911S had a very early version of the M-Caliper. It had funny wings on it and it did not have compensating lines on the front… only on the rear. I have a pair in the shop now so I'll try to grab some quick pictures. The rears on the 67 911S are Wide L-Calipers. I did a write up of the differences between the L-Caliper and the Wide L-Caliper which can be found here:

http://www.early911sregistry.org/forum/sho...ead.php?t=20424

Rob... I think they came on these cars. (IMG:style_emoticons/default/wink.gif)