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:

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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.

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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):

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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:

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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??

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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:

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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.:

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

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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:

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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.:

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

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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!):

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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.

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.

Eric,

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










OK, not really.

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

That would be a first... I'm fairly certain Jeff dropped the brain bomb here.

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

Damn, I get such an education from reading these posts! 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...

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!)

Seriously Eric, great information! Thanks for sharing this!

Thanks E.

One more measurement from this AM:

There was 3mm (1/8th of an inch) shaved in radius off the tops.

Can't wait for the WCR


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

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...

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.

Were's that jaw-drop smiley?

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.

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

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.



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.

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I like that quick change feature for the pad pins... Any chance PMB will manufacture something to convert the more common 4 cylinder brakes and M calipers to a quick change feature. Great for track days...

!!!

I am going the 908 route. After digging thru books and hunting around my first conclusion is brakes were a hodge podge in the race department except on the top tier cars. Different cars, different wheels. What worked at the time were installed. We all know if something didn't fit they made it fit by whatever means necessary. Over the years as cars may have been parted out or upgraded parts ended up on other cars as they were passed down unto other hands. Throw in that ATE, Girling, AP were all players in the stopping business.

I do think this caliper of yours is a unique specimen. The V stamp still has me thinking. Porsche used a V for "Versuch" on many parts meaning experimental. If it was a pre-production unit without a cast part number the V would normally be found. The other alternative to V would be "Verderachse" meaning front axle. A werks 908 weight sheet signed off by Hans Metzger in 1968 confirms both the V designations were used.

Now for some brake caliper fun. Digging around many variants were used front and rear. I have tagged them as they were found. Enjoy!

continued

for comparison and historical fun here are the big boys which could never be mistaken for an S caliper.

OK... now we're really mix'n it up here in brake-land.

The ones marked 911 S, ST (in your first picture post) seem to be the 910 calipers.

The 911ST Caliper is the same as my early S-Caliper (no round indents with the x and notice the cutouts around the bleeder and compensating lines on the inside. This appears to be the exact same caliper I have.

VERY INTERESTING on the 908 caliper grouping as I see two things that I've never seen before with a 908 caliper. While the pad spring is all 908, the nose of the caliper falls more in line with your picture of the later S-Caliper (more on that in a sec.). I've never seen that bull nose pre-1972.5 caliper. I've also never seen the dichromate finish pre 1972.5 either. Very cool pictures which raise big questions for me.

The S picture shows a glass bead blasted S-Caliper that should have the dichromate finish. It has the round indents with the "x" which denote it as post 1970.

Wow... cool stuff.

Rob, I will be making a batch of 12 (possibly more) of the 910 style quick change assemblies. We have a pair of early style S-Calipers coming to perform the mod on. I think it will be fun. It will only be for S-Calipers though...

In the "continued" post.

1. 1972.5 and on Dichromate S-Caliper
2. Early 1969-70 S-Caliper

The rest of that stuff makes me dizzy.

Yup and a headache! Trying to find the pic of a 6 pot used on the 917 30 that is a beast.

The calipers marked 'early 917 late 908' are the Girling caliper.
The calipers marked '908 914GT 911ST' are very weird. Bull-nose, no pin holes, appear to be genuine 908 construction, but what are the holes in the middle of the lower bridge?

The S caliper progression as I understand it goes:
910 style with a round end cap
standard S caliper with 4 bolt rear cap, no circles on top of bridges
the same as above but with circles
the same as above but with X in the circles
the bull-nose version with X in the circles.

variants:
910 caliper could have two pins, or one U pin
908 caliper had the spring loaded pin

I wouldn't include the 910 caliper as an S-Caliper... way too different. I would include your caliper and the 908 caliper as in every basic mold from those, they are exactly like the S-Caliper. I'll modify your text to what I'm thinking:

908 Caliper w/910 pad pins. (your caliper, kinda what I was eluding to in the thread title)
908 Caliper Spring loaded and solid bottom load.
________________________________________This ends the racing protoypes of this caliper.

1969 - Standard S caliper with 4 bolt rear cap, no circles on top of bridges. Clear anodizing (I believe your caliper was anodized with some areas recently scratched off for cleaning etc.)

1971 - The same as above but with circles with X. This denotes a new style piston and was used from that point forward. I've never heard of the circular indent without the "X".

1972.5 - The bull-nose version with X in the circles and dichromate sealant.

Cool thread. Love the pictures of the calipers. RSR caliper, cooling fins?

You will shortly since that set will be the ones destined for modification.

some info on the 917 calipers:
http://forums.pelicanparts.com/showthread.php?t=87025

LOL... this is getting crazy! I love it. Makes sense though. The "X" was to denote a piston change. I'l bet they used up the old ones then started the "X" sequence with the first new piston set.

That's another odd-ball caliper. You must hang a pork chop around your neck and they all flock to you.

Maybe Daves caliper goes with these?........and I have two sets!

I'm fairly certain one set goes on my car...

Jeez, I'll have to remember not to ever get in a tech quiz with youz guys.

No worries mate, I've forgotten 80% of what I once knew.

Here are a couple of shots of the non X 'S' caliper:
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fairly typical to have something like a serial # and an operators stamp in an outline
We need to start a list of these marks to see how many varieties there are.
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other bridge circle
We'll also have to start trying to get VIN's from the cars these came off of to try and determine a time line of varieties.

That's a weird indent too. Much more angular or pronounced than the others...

Here's the very early 911S M-Caliper with the spacers. For edification; they are posted sided by side with a more common M-Caliper:
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Full on top view. See the "wings" front and rear?:
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Here they are from the side. I would say they add structural rigidity and possibly cooling?:
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And the back:
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And the Wide L-Caliper. These are very difficult to build as there are no kits for them any more and in many ways (not all though) they are simply bored out L-Calipers. This makes the dust cover mounting area very fragile. If the pistons are rusted in... it can be lights out for a very rare caliper:
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With the unique dog-bone spacers used to center the caliper over the newly vented rear rotor:
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Those calipers look gawd awful. Send them up, and I'll pretty them up for you.

BTW, the fellow (Gerhard (Gary) Hirsh) I got the race caliper from did indeed own 9140430033 for a short time, however the last time I saw the car it had the proper 908 calipers on it. I suspect the race caliper came on some other, earlier, race car however I don't recall all the cars he drove.

Is he around?

Somewhere near Toronto I understand.

We should try to look him up (unless you still owe him money) It would be nice to see if he has any recollection of the caliper. It may help us find it's mate.

I'm fairly certain we've narrowed this down to a 908 caliper. I would say it's a fairly rare 908 caliper as well. All of the logo markings are in the exact locations for 908 and the shaved top says 908 as well. The only thing that doesn't is that 910 style pin and "most" of the 910 calipers I've seen now don't even have an endurance pin.

908 being the predecessor to the production S-Caliper (virtually one in the same), I think this is one of the first from this casting but... that is PURE speculation based upon the pin vs. the spring loaded pad mechanism.

Thoughts?

here is an interesting thread I came across in my research:
http://forums.pelicanparts.com/showthread.php?t=169568
I have a few emails out to the fellows involved trying to learn more.

It would appear that the caliper evolved from the 910 style with the round back cover to the more familiar S caliper.
Varieties of the caliper were made to suit particular applications.
The most familiar 908 variety with the bottom pins and plate was an endurance caliper with thicker pads. However the single pin for pad release seems to stick out quite a bit, and may not be suitable for rims less than 15" diameter. My caliper is shaved down and would fit smaller rims better. Therefore I think we need to look at cars that used the smaller rims.

Going back to my original post.........Hans Metzger of Porsche typed model 906/2000 which was known as the Ollon-Spyder. This model first appeared at the Swiss Ollon-Villars hillclimb event. Metzger took inspiration from the Elva-Porsche. This model used exclusivly 13 inch front wheels. Porsche at the time did not make 13 inch wheels and had them produced from an outside source along with revamped uprights. The original wheels were steel would have had a barrel thickness of approx 1/4 an inch. This would have meant shaving any parts including calipers to clear the new wheels. The steel wheels used a reinforced center section extending into the barrel shell requiring even more clearance. The calipers at the time would have to have been experimental or cast and machined for the smaller wheels. As well as the prototypes class (called group 6) aimed at the big manufacturers they also defined a class for competition sports cars (class 4) where a minimum production number of 50 cars was permitted. Piech saw an opportunity in the new ruling, but was convinced that Porsche would need a completely new chassis and car. He decided to use the Ollons-Villar spaceframe chassis (not the 904) as a starting point.

The 906 (or Carrera 6) used both steel wheels and magnesium. Applications included 13 inch wheels for up to 2.0 liter versions. The Daytona running 910 also used 13 inch wheels and would have had to use the early shaved calipers. The long tails had brake cooling issues and were than updated with 4 piston calipers and ducts to alleviate cooling problems at the high speed course's. In late 1968 some calipers were updated again to magnesium bodies from the previous aluminum versions for weight savings. Porsche returned to aluminum calipers as the magnesium versions had problems associated with high heat. Even later updates on the 908 and then 907's all wheels were updated to 15 inch. This allowed the use of larger calipers and ventilated brakes to be utilized. The 908 with updated wheels and calipers stopped better than any other previous racing Porsche.

Based on the factory documentation and Erics' information the timeline is narrowed even more on Dave's caliper. Based on the inspection marks I honestly believe he has a real Mccoy 908 racing caliper and not one that appeared on a 914 GT as off the shelf racing parts. Adding Porsche has always used the 20% safety margin (or over-build) on it's racing parts unless unavoidable. I cannot see a logical reason for the factory to shave calipers unless it was for smaller diameter wheels. The factory never skimped on brakes. The 907 units used entirely different calipers and then that eventually evolved into the 917 model.

910 - 1967
907 - 1967-1968
908 - 1968-1969
S-Caliper - 1969

I'm not sure about the shaved thing Jeff. I agree totally however, all of the 908 calipers I've seen have the shaved top.

I'm going to call this one of the very first 908 calipers. As the 910 caliper (and it's endurance pin mechanism) evolved, the 908 caliper came to be. I'm going on a limb and saying; this 908 caliper, as one of the very first, received the 910 pin assembly. Subsequent 908 calipers had the single pull pin spring.

When you look at the time line above and the pictures from the 910 manual... it starts to become obvious. Dave is on possion of one if the very first 908 calipers ever made. Want to bring the thread full circle? This is one of the very first S-Calipers ever made, as 908 calipers are really nothing more than an S-Caliper. Amazing history when you consider the success of the 908 Caliper and the S-Caliper.

Dave, I found the original owner of that GT as well. Good conversations all around. Thanks guys.

E.

Been busy cloning things...

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Very nice. They will look even better in person.

I see you finally have got my calipers done!