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914World.com _ 914World Garage _ Brakes
Posted by: johnmhudson111 Jul 28 2005, 08:11 AM
Coupe of questions about brakes. First of all what is the difference between "M", "A", and "S" capliers? Is it the mounting bolt distance? Early vs.Late? 
Did the 914/6 come with "M" capliers? If not what did they come with? Can these brakes be upgraded to something like the "big reds?
Posted by: ClayPerrine Jul 28 2005, 08:27 AM
M caliper. Cast iron 2 piston caliper. Uses 3" bolt spacing. Used on 73 and older 911, 914 and 914/6. Used with a spacer for the vented rotors. Same piston bore, pad size, and bolt pattern as the 914/6 rear caliper.
S Caliper. Aluminum 2 piston caliper. Uses 3.5" bolt spacing. Used on 74 and later 911 S and all 911s with sportomatic. Bigger pads than the M caliper. Had problems with corrosion in the piston bores. Rebuilt ones use a stainless steel sleeve to alleviate this.
A Caliper. Same as the S caliper, but made from cast iron. Bigger pad sizes than the M caliper.
As for upgrading to "Big Reds", you would have to put 74 and later 911 struts on the front to get the correct bolt spacing to fit the caliper, and you have to have 17" wheels for caliper clearance.
My suggestion.. Boxster (Not Boxster S) Monoblocks. There are bolt on adapters for them, and you can fit them under 16" wheels. But you still have to have the 74 and later 911 struts with the 3.5" bolt spacing.
My question to you.. how much brake do you REALLY need? Can you lock the wheels up now? Do you plan on running on a track where you would heat the brakes up enough to warrant the big increase in unsprung weight?
Posted by: johnmhudson111 Jul 28 2005, 08:47 AM
| QUOTE (ClayPerrine @ Jul 28 2005, 09:27 AM) |
| M caliper. Cast iron 2 piston caliper. Uses 3" bolt spacing. Used on 73 and older 911, 914 and 914/6. Used with a spacer for the vented rotors. Same piston bore, pad size, and bolt pattern as the 914/6 rear caliper. S Caliper. Aluminum 2 piston caliper. Uses 3.5" bolt spacing. Used on 74 and later 911 S and all 911s with sportomatic. Bigger pads than the M caliper. Had problems with corrosion in the piston bores. Rebuilt ones use a stainless steel sleeve to alleviate this. A Caliper. Same as the S caliper, but made from cast iron. Bigger pad sizes than the M caliper. As for upgrading to "Big Reds", you would have to put 74 and later 911 struts on the front to get the correct bolt spacing to fit the caliper, and you have to have 17" wheels for caliper clearance. My suggestion.. Boxster (Not Boxster S) Monoblocks. There are bolt on adapters for them, and you can fit them under 16" wheels. But you still have to have the 74 and later 911 struts with the 3.5" bolt spacing. My question to you.. how much brake do you REALLY need? Can you lock the wheels up now? Do you plan on running on a track where you would heat the brakes up enough to warrant the big increase in unsprung weight? |
I plan on taking the car to DEs and to AutoX but no club racing.
The reason I was asking about the difference in the capliers and the related struts was to get insure that I didn't buy a set of struts that locked me into having to no options. It looks like I need to stick with 74 or later strut.
Thanks!
Posted by: ClayPerrine Jul 28 2005, 09:03 AM
Just make sure you don't get stuck with a set of Hydro-Pneumatic struts.. They were a POS right out of the factory....
Posted by: johnmhudson111 Jul 28 2005, 09:05 AM
| QUOTE (ClayPerrine @ Jul 28 2005, 10:03 AM) |
| Just make sure you don't get stuck with a set of Hydro-Pneumatic struts.. They were a POS right out of the factory.... |
How can you tell them from regular struts?
Posted by: ClayPerrine Jul 28 2005, 09:33 AM
The hydro-pneumatic struts were quite a bit bigger in diameter, and look completely different from the standard 911 strut.
Simple, If it doesn't look like a 914 strut with different bolt spacing, don't buy it.
Posted by: johnmhudson111 Jul 28 2005, 09:43 AM
| QUOTE (ClayPerrine @ Jul 28 2005, 10:33 AM) |
| The hydro-pneumatic struts were quite a bit bigger in diameter, and look completely different from the standard 911 strut. Simple, If it doesn't look like a 914 strut with different bolt spacing, don't buy it. |
I have been looking at a couple of different listings on evil-bey one for a set off a 77 911. I would think they would be a good starting point. If I can get them.
Posted by: Oled Jul 28 2005, 10:34 AM
I have Boxster calipers on the front of my 914 on '89 carerra struts. Widened 914/6 calipers on the rear and ventilated discs all around. I can lock up the front wheels to easily, even on the strack with new race tires on the car. On the street it would be dangerous for a different driver who would expect normal brake response. i am thinking about taking off the Boxster caliper and putting A's on the car. Several years ago I found a great deal on Ebay for these new in the box calipers and since my car has not run for a year and a half now, they are hardly used.
Posted by: johnmhudson111 Jul 28 2005, 12:20 PM
| QUOTE (Oled @ Jul 28 2005, 11:34 AM) |
| I have Boxster calipers on the front of my 914 on '89 carerra struts. Widened 914/6 calipers on the rear and ventilated discs all around. I can lock up the front wheels to easily, even on the strack with new race tires on the car. On the street it would be dangerous for a different driver who would expect normal brake response. i am thinking about taking off the Boxster caliper and putting A's on the car. Several years ago I found a great deal on Ebay for these new in the box calipers and since my car has not run for a year and a half now, they are hardly used. |
Looks like I am going to be getting the struts from that 77 911. It has the "A" capliers, want to trade?
Posted by: Eric_Shea Jul 28 2005, 08:40 PM
Ahhhhhhhhhhhh Hello, Clay...
S-Calipers arrived a tad before 74 Uncle Clay 
There's no such thing as a stainless sleeve for an S-Caliper. Stainless pistons are the trick. The corrosion in the bore "generally" isn't the problem it's the corrosion on the piston where it sits in the bore and rests against the seal (picture included)
A-Calipers don't look anything like an S-Caliper (it's twu, it's twu). Same pad surface area but not as deep as an S-Pad. This is such a common myth. They look like they're from different manufacturers. They look more like the BMW Calipers people are using than they do an S-Caliper.
M-Calipers were never (ever) used on 914's (post 73 or whatever), they were stock on 914-6's and 911T's though. And the bore is about 5mm larger than a 914-6 (me believes... I can confirm if desired)
Other than that "You're SPOT ON Clay" 
John, what engine do you have? If it's a -4, I wouldn't go with anything larger than an M-Caliper. I have my reasons which I'll go into detail if you really want to know. Many, many BTDT experiences.
Attached image(s)
Posted by: johnmhudson111 Jul 29 2005, 07:43 AM
| QUOTE (Eric_Shea @ Jul 28 2005, 09:40 PM) |
| John, what engine do you have? If it's a -4, I wouldn't go with anything larger than an M-Caliper. I have my reasons which I'll go into detail if you really want to know. Many, many BTDT experiences. |
Right now I have a 1.8 4 in the car but this will be replaced at some point with a 6 in the future. The plan right now is a nice 3.0 or 3.2. I will be upgrading the suspension and the brakes with that in mind, the engine will be the LAST big upgrade. I have the 5 bolt conversion kit for the rear comming from you and I just bought a 911 front suspension off a 77 with "A" capliers. I am thinking that going with Boxster monoblocks down the road would be the best solution...
Posted by: Eric_Shea Jul 30 2005, 09:08 AM
Based upon your future plans it sounds like you're on the right track. You're going to have a hard time getting the rears to work right now. Take out the P-Valve and put a T-Fitting in there for sure.
You're now into the "Rear Handbrake Black Hole". Enjoy, and sort your options. If'n I was you, I'd max out at Carrera brakes ala. Sir Andy. Proque? You go with the Monoblocks and you'll have to weld on a new ear on those shinny new control arms (that are "still" waiting for the bushings to arrive... I'm going to see if I can have them next-day air them... sorry). If you plan on big tires etc you'll still have enough stopping power to lock them up. I'll bet Andy's happy with his set-up. Ask.
I'll have a 200-220hp -6 in my GT with S-Calipers up front and 911 M-Calipers in the rear (T-Fitting). I'm using the 911 handbrake assembly. Same basic setup that came on a 76 930 (with 240hp and a similar 7 & 8 x 15 wheel/tire package)
Posted by: johnmhudson111 Jul 30 2005, 01:29 PM
| QUOTE (Eric_Shea @ Jul 30 2005, 10:08 AM) |
| I'll have a 200-220hp -6 in my GT with S-Calipers up front and 911 M-Calipers in the rear (T-Fitting). I'm using the 911 handbrake assembly. Same basic setup that came on a 76 930 (with 240hp and a similar 7 & 8 x 15 wheel/tire package) |
Eric - No rush on the rears, so just send them out normally once you get them together.
Until I started looking into this upgrade I never thought you could have too much brake on a car.
Would the "stock" 914/6 brakes for the rear and the boxster monoblocks for the front be a workable package?
Posted by: Dan (Almaden Valley) Jul 30 2005, 01:49 PM
I am interested in this thread since I am considering the 5 bolt set up and brake up grade.
I was thinking of a SC/Carrera front suspension with associated brakes.
Is is best to use a matching SC/Carrera rears for best balance? Not to mention ventilation?
Eric, Can you adapt your 5 bolt rear setups for a later style caliper and offset? Ears welded for 3.5 mounting spacing?
Is it preferred to just use the 914 rears or put the fronts on the rear?
I know, questions questions questions!
Thanks 
Posted by: ClayPerrine Jul 30 2005, 02:31 PM
| QUOTE (Eric_Shea @ Jul 30 2005, 09:08 AM) |
| Based upon your future plans it sounds like you're on the right track. You're going to have a hard time getting the rears to work right now. Take out the P-Valve and put a T-Fitting in there for sure. You're now into the "Rear Handbrake Black Hole". Enjoy, and sort your options. If'n I was you, I'd max out at Carrera brakes ala. Sir Andy. Proque? You go with the Monoblocks and you'll have to weld on a new ear on those shinny new control arms (that are "still" waiting for the bushings to arrive... I'm going to see if I can have them next-day air them... sorry). If you plan on big tires etc you'll still have enough stopping power to lock them up. I'll bet Andy's happy with his set-up. Ask. I'll have a 200-220hp -6 in my GT with S-Calipers up front and 911 M-Calipers in the rear (T-Fitting). I'm using the 911 handbrake assembly. Same basic setup that came on a 76 930 (with 240hp and a similar 7 & 8 x 15 wheel/tire package) |
The boxster monoblocks use an adapter block available from Rich Johnson that will allow them to bolt to the existing tab on the trailing arm.
Posted by: Andyrew Jul 30 2005, 02:35 PM
I've got A calipers and stock rears with vented rotors all the way around and racing pads....
Stops good, but no where near the stopping ability of ABS.... lol
I get one tire to lock up too soon... sucks....
Posted by: michel richard Jul 30 2005, 02:36 PM
| QUOTE (johnmhudson111 @ Jul 30 2005, 11:29 AM) |
| Would the "stock" 914/6 brakes for the rear and the boxster monoblocks for the front be a workable package? |
And the problem with the stock 914/6 rears is that they are very very difficult to find. And there's apparently a couple or Ferrari models on which they fit . . . but I dunno if that's a big fator.
Posted by: Aaron Cox Jul 30 2005, 02:38 PM
| QUOTE (ClayPerrine @ Jul 30 2005, 01:31 PM) | ||
The boxster monoblocks use an adapter block available from Rich Johnson that will allow them to bolt to the existing tab on the trailing arm. |
one more correction to uncle clay's knowledge...
monoblocks from a boxster fit under 15" cookie cutters...... ive seen it
Posted by: johnmhudson111 Jul 30 2005, 02:38 PM
| QUOTE (ClayPerrine @ Jul 30 2005, 03:31 PM) |
| The boxster monoblocks use an adapter block available from Rich Johnson that will allow them to bolt to the existing tab on the trailing arm. |
Clay, How can I get in touch with Rich? And which rotor do you have to use on the rear with the monoblocks?
Posted by: Aaron Cox Jul 30 2005, 02:39 PM
paragob products has the adapter / rotor / new calipers setup for ~900 or so....
Posted by: johnmhudson111 Jul 30 2005, 02:42 PM
| QUOTE (michel richard @ Jul 30 2005, 03:36 PM) |
| And the problem with the stock 914/6 rears is that they are very very difficult to find. And there's apparently a couple or Ferrari models on which they fit . . . but I dunno if that's a big fator. |
From what I have read here, you can use the stock 914/6 rotors with the 914/4 capliers. That is my plan right now. I ordered the rotors from Pelican Parts for around $75 a piece.
Posted by: michel richard Jul 30 2005, 05:17 PM
| QUOTE (johnmhudson111 @ Jul 30 2005, 12:42 PM) |
| From what I have read here, you can use the stock 914/6 rotors with the 914/4 capliers. That is my plan right now. I ordered the rotors from Pelican Parts for around $75 a piece. |
I believe you are correct. The difference is that the caliper pistons are larger diameter on the /6 rears. Not something that will interfere with fit.
Posted by: Dave_Darling Jul 30 2005, 06:08 PM
Some people have found that there is a tiny bit of interference between the stock -six rotor and the stock -four caliper. It might even be that there is some casting flash on the -four caliper that hits? Not sure. But in a few cases, people have filed the bridge of the caliper just enough to clear the rotor. Make sure to leave a little extra space because the rotor grows just a bit when you warm it up...
Of course, if you cut too far you get into the brake fluid passages--and then your rear brakes are f***ed. So be careful.
The interference doesn't happen in all cases, but it's something to watch for. You may be able to use whatever slop there is (if any) in the caliper mounting to get them moved outward just a bit...
--DD
Posted by: ClayPerrine Jul 30 2005, 09:27 PM
| QUOTE (johnmhudson111 @ Jul 30 2005, 02:38 PM) | ||
Clay, How can I get in touch with Rich? And which rotor do you have to use on the rear with the monoblocks? |
E-mail him at a914guy@aol.com
It uses the 24mm Carrera rotor.
Posted by: Dead Air Jul 30 2005, 10:53 PM
Slow down and you would'nt neeed brakes!
Posted by: Oled Jul 31 2005, 09:19 AM
My Boxster front calipers are used with 15x7 cookie cutters on the track and 16" phone dials on the street.
Posted by: Mueller Jul 31 2005, 09:34 AM
| QUOTE (Oled @ Jul 31 2005, 08:19 AM) |
| My Boxster front calipers are used with 15x7 cookie cutters on the track and 16" phone dials on the street. |
Hi Ed,
How is the MS and turbo project going???
As for the calipers having too much initial bite, how about installing different pads? Not sure if a cheaper less aggressive pad is available or not.
Posted by: Series9 Jul 31 2005, 11:49 AM
Here's too much brake on a 914. They work GREAT, but I have to be the ABS:
Attached image(s)
Posted by: Oled Jul 31 2005, 03:42 PM
Mike,
Good to hear from you. I started off with padgid OEM pads but they squealed like hell no matter what I did. I then put on FLAPS specials and still have too much stop.
Been trying to get a new business venure running for the past year so my car has been paying hommage to the land of my youth and has been up on blocks for a year. I am going to redo my MS to the newer 12x12 variety. I have a Subaru water to air intercooler off or a jdm car and am now trying to get a decent tubo mount, air tube, and water plan for the turbo. Also I am trying to get an installation of a water tank, pumps, and then coolers in the front bumper that looks somewhat professional and not just like a cobbed up chop job. The midwest 914 meet is labor day but that is an almost unobtainable goal but who knows.
Posted by: Oled Jul 31 2005, 04:02 PM
Total piston area on various calipers
M, S, A Front, 914/6 front 5.61 sq in
64-68 M rear 2.98 sq in
69-83 M Rear 914/6 Rear 3.52 sq in
84 on M Rear 914/4 Front 4.29 sq in
Boxster Front 7.05 sq in
Boxster Rear 5.73 sq in
Posted by: Eric_Shea Jul 31 2005, 04:39 PM
Joe,
That's a "HUGE" brake line. Do you use the Mercedes (truck) 72mm Master Cylinder? You know, the Cap'n doesn't recommend braided lines. 
OK, enough "Gaiety" on to the questions:
John - Your control arms are done. I cleaned out the shop today and found a set of bushings that were slated for another job that got shelved. They should ship tomorrow.
| QUOTE |
| Is is best to use a matching SC/Carrera rears for best balance? Not to mention ventilation? |
Sure. You'll need a spacer to either fit under your rotor -or- if there's enough room between your caliper and control arm (on 914 calipers there isn't) you could put the spacers in between the mounting ears and the caliper. If it's a 24mm Carrera rotor "I Believe" you'll need a 9mm spacer. If it's a standard 20mm vented (SC) rotor then it will be a 5mm spacer. You'll also need to figure out what to do about your hand brake.
I always think it's best to stick with what the Porsche engineers felt best in a "system".
| QUOTE |
| Eric, Can you adapt your 5 bolt rear setups for a later style caliper and offset? Ears welded for 3.5 mounting spacing? Is it preferred to just use the 914 rears or put the fronts on the rear? |
We can do it all... it just takes money
Seriously, weigh what it would cost for an additional ear and the welding and then look at Rich's mounts. I like to use 914 rears up to a point:
1. Stock 914 Rears with 911 M-Calipers up front and a T-Fitting.
2. Modified 914 Rears (Our V-Caliper) for a vented rotor with 911 S or A-Calipers up front.
3. Beyond (or even with) an 911 S or A-Caliper, I would consider using a different rear brake. A 914 -6 brake is a good choice but very hard to find. You're still limited to a 38mm piston. It seems to be working for Oled but I tend to doubt those rears are even contributing, but hey... with those fronts, who needs rears?
Porsche only used the 38mm rear up to 1984. Then they went to 42mm. (then they had to use a pressure regulator). I'm not sure of the "Boxster" system. I would think it would be great for a mid-engine 914 with a 3.2 or 3.6. The teener is obviously much lighter and should benefit tremendously from that system.If you subscribe to the "Bigger-is-Better" school, I imagine you can bolt damn near anything you want on a 914. They'll grab those big rotors and stop them quick. If you've got enough meat under your car this may make sense. If not, you won't be able to outbrake anyone anyway... your tire will break the contact patch, your wheel will lock up and while they're stopping, you and your big-ole brakes will be sliding right on by.
I like "systems". I like "systems" put together by Porsche engineers. Again, mine's fairly vintage (cause I wanted it that way) and it approximates the "system" used on a 76 930 with roughly the same horsepower (on a heavier car) as I'll be using. The only problem with "systems" and 914's is the Handbrake.
My $0.02
Posted by: Eric_Shea Jul 31 2005, 04:52 PM
And I know what you guys are thinking, after looking at Ed's list: But...
The 911 Front M-Caliper will not bolt on the rear. The nose is too big for the hat on the rear rotor.
Posted by: Dan (Almaden Valley) Jul 31 2005, 05:51 PM
| QUOTE (Eric_Shea @ Jul 28 2005, 06:40 PM) |
| Ahhhhhhhhhhhh Hello, Clay... S-Calipers arrived a tad before 74 Uncle Clay There's no such thing as a stainless sleeve for an S-Caliper. Stainless pistons are the trick. The corrosion in the bore "generally" isn't the problem it's the corrosion on the piston where it sits in the bore and rests against the seal (picture included)A-Calipers don't look anything like an S-Caliper (it's twu, it's twu). Same pad surface area but not as deep as an S-Pad. This is such a common myth. They look like they're from different manufacturers. They look more like the BMW Calipers people are using than they do an S-Caliper. M-Calipers were never (ever) used on 914's (post 73 or whatever), they were stock on 914-6's and 911T's though. And the bore is about 5mm larger than a 914-6 (me believes... I can confirm if desired) Other than that "You're SPOT ON Clay" John, what engine do you have? If it's a -4, I wouldn't go with anything larger than an M-Caliper. I have my reasons which I'll go into detail if you really want to know. Many, many BTDT experiences. |
Eric,
What are your reasons you prefer the M calipers and stock rear 914 brakes on a 4 cylinder?
I plan on doing alot of TT/DE with my car once it has completed.
I am interested in your reasoning as my next modification for the car will be suspension.
I plan on going with a 911 front suspension and your 5 bolt control arms on the rear.
The motor will be basically a stock motor with the possiblilty of going to a 2056 in the future.
Our longest sessions run about 30 mins. I like to have a nice hard pedal for as long as possible.
Master cylinder of 19mm or larger?
Braided stainless or stock rubber brake lines?
Comments are welcome.
Posted by: redshift Jul 31 2005, 06:11 PM
| QUOTE (Eric_Shea @ Jul 31 2005, 06:39 PM) |
| OK, enough "Gaiety" on to the questions: |
not that there is anything wrong with that..Posted by: Oled Jul 31 2005, 07:52 PM
i left one off of the first list. I have added the diameter of the pistons
Total piston area on various calipers
M, S, A Front, 914/6 front 5.61 sq in (48mm)
64-68 M rear 2.98 sq in (35mm)
914/4 Rear 2.65 sq in (33mm)
69-83 M Rear 914/6 Rear 3.52 sq in (38mm)
84 on M Rear 914/4 Front 4.29 sq in (42mm)
Boxster Front 7.05 sq in (2 sets @40mm)
Boxster Rear 5.73 sq in (2 sets @30mm)
Posted by: Eric_Shea Jul 31 2005, 08:55 PM
Damn it Miles... you blow my cover and all hells gonna brake loose.
Hey Dan,
| QUOTE |
| What are your reasons you prefer the M calipers and stock rear 914 brakes on a 4 cylinder? |
Generally, I don't. I prefer stock 914 brakes on a -4 but, if you're going 5-lug and you're keeping a fairly stock engine and stock fenders then I don't think anything larger than an M-Caliper is needed. When I said previously "I have my reasons..." they revolve around that list I provided above and the many cascading problems one get's into when trying to put larger calipers on a 914. That being said, tires have gotten better since 1970-76. Brake pads have gotten better too... so:
1. The brakes on a stock 914 rock "if" they're working properly. With new pad compounds I think they can match the newer and wider tires people are using without a problem.
2. If you're going 5-lug then get an early 911 front end that has M-Calipers and vented rotors (ala the 914-6). I prefer 70-73 because of the newer ball joints and thru-body bar setups.
3. If you haven't changed your contact patch substancially (GT Flares and big wheel and tire packages) then you should be fine with M-Calipers and the smaller 914-4 rear caliper. Remember, Porsche went to a larger 38mm piston in the rear when they put the M-Calipers on. This is why I recommend replacing the P-Valve with a T-Fitting if you go M-Caliper and Stock rears. If you can find a set of 914-6 rears, all the better, keep the P-Valve (although they can be a pain when it comes time to bleed), I would prefer that setup.
4. Once you go beyond an M-Caliper, you really need to address the rears. A T-Fitting and a V-Caliper will work but you should really be in the 38mm range minimum. Now begins the cascade. This is why I say; "If you have a -4, I prefer M-Calipers and nothing larger.
The Cascade:
There's two calipers that are made to work on the rear of a 914. The ATE 914 caliper and the now uber rare 914-6 caliper. The -4 has a 33mm piston and the -6 has a 38mm. What do we mean when we say "made to work"? Handbrake. If you're not concerned about a handbrake then go back out to the garage and start bolting all sorts of calipers on your car. If you are then you're stuck. Either:
A. Stay with a front caliper that won't overpower your rears. (M-Caliper)
B. Find some 914-6 Calipers.
C. Go with an alternate handbrake assembly and "load-em-up".
Both B and C can be expensive alternatives. I went with a 911 rear handbrake (see classics thread, not entirely easy but not hard either). The trick is getting cables after you go that route. There's been a recent thread where someome has been looking into having them made up. So, 911 handbrake assemblies? $100.00. Rear M-Calipers? $50-75, probably need to be rebuild... Cables? $150.00. New Rotors? $125.00. Custom Spacers? $80.00 You're in it for about $600.00 when you buy the rebuild kits etc. -or- you can keep your stock rears and don't go bigger than an M-Caliper (cause your tires and engine don't really require it).
I just saw a set of -6 calipers go for $400.00
Keep your eyes peeled. Those and a T-Fitting and a set of A or S-Calipers and you should be fine. -or- you can keep your stock rears and don't go bigger than an M-Caliper (cause your tires and engine don't really require it). See a pattern?
Posted by: Porsche Rescue Jul 31 2005, 09:34 PM
Next question: How can I tell the difference between stock 914-4 front caliper and an M caliper? Is there a visual difference with the caliper installed?
"Das Boot" is about to receive a 2.7 six. It still has 4 bolt hubs turning 7 x 15 Revolution wheels with 205x50 Victor Racers for AX/DE. The car is track modified so I don't know what calipers I have. Rears are stock 4 cyl. I don't want to change hubs/wheels/tires if I don't have to. However I want the car to stop when asked.
Posted by: Eric_Shea Jul 31 2005, 09:45 PM
Well... an M-Caliper wouldn't necessarily fit on a -4 strut due to offset differences so "installed" it wouldn't be an issue. If it's sitting on a -4 rotor it's probably a -4 caliper.
Another visual would be spacers. An M-Caliper of the era you're thinking about would have a 9mm spacer in it and it would be sitting on a vented rotor. (Early 911's had M-Calipers on solid rotors and no spacers). They're "larger" overall across the back and the nose cone to accomodate the larger pistons. And, the M-Caliper will have only 1 bleeder. Mass produced 411/914 calipers had two bleeders so they could interchange for left or right.
Otherwise... they look pretty damn similar. 
Go look... there's a yellow car in your garage with M-Calipers on it!
Posted by: Porsche Rescue Aug 1 2005, 08:34 AM
Duh! Stock six front is early "M" with no spacer and solid rotor, correct? (I will compare but haven't had my coffee yet).
The orange car I had before I bought Ida had 914-4 front calipers moved to rear (I used a 2x4 for an ebrake and didn't like it). I was told the fronts were 911. Does that mean it had 911 struts?
Posted by: johnmhudson111 Aug 1 2005, 08:41 AM
| QUOTE (Porsche Rescue @ Aug 1 2005, 09:34 AM) |
| The orange car I had before I bought Ida had 914-4 front calipers moved to rear (I used a 2x4 for an ebrake and didn't like it). I was told the fronts were 911. Does that mean it had 911 struts? |
Interesting, will the /4 front caplier simply bolt up to the rears? It couldn't be that easy, could it?
Posted by: Mueller Aug 1 2005, 09:14 AM
actually you can use -M front calipers on a /4 strut...of course you need the mythical billet hubs
Hey E,
Why won't the -M (front) caliper work on the rear trailing arms??
| QUOTE |
| Interesting, will the /4 front caplier simply bolt up to the rears? It couldn't be that easy, could it? |
yes, however, you lose your e-brake....
Posted by: Dave_Darling Aug 1 2005, 10:41 AM
| QUOTE (Porsche Rescue @ Aug 1 2005, 06:34 AM) |
| Duh! Stock six front is early "M" with no spacer and solid rotor, correct? (I will compare but haven't had my coffee yet). |
Nope, the stock Six had M calipers and ventilated front rotors.
| QUOTE |
| The orange car I had before I bought Ida had 914-4 front calipers moved to rear (I used a 2x4 for an ebrake and didn't like it). I was told the fronts were 911. Does that mean it had 911 struts? |
911 front hubs will not fit on 914 struts--so yes, it had 911 struts.
--DD
Posted by: Eric_Shea Aug 1 2005, 11:52 AM
| QUOTE |
| Duh! Stock six front is early "M" with no spacer and solid rotor, correct? (I will compare but haven't had my coffee yet). The orange car I had before I bought Ida had 914-4 front calipers moved to rear (I used a 2x4 for an ebrake and didn't like it). I was told the fronts were 911. Does that mean it had 911 struts? |
What Dave said... -or- it had those prototype "Mueller Hubs" on there. (had to throw "Mueller Hubs" in there in case Brad is reading
) No additional charge for the overnight brake upgrade BTW. Go get your Java! | QUOTE |
| Interesting, will the /4 front caplier simply bolt up to the rears? It couldn't be that easy, could it? |
What Mike said... So now the problem is, why have a caliper with 42mm worth of piston but doesn't reside on top of a big-ole vented rotor? So, the solution is go with the "Carrera SYSTEM" and keep the P-Valve in the car. In 84 Porsche moved to that system in the 911. P-valve and all. The percentages varied over the years but I think the 84-89 Carrera was something like 33%. Look for a handbrake as well.
Posted by: Porsche Rescue Aug 1 2005, 12:27 PM
Had my coffee. Here's what I see so far. Front calipers on my conversion car have one nipple, no spacer and solid rotor.
Ida, as you taught me, has spacer and vented rotor, 1 nip.
Took camera to garage to shoot the "mystery" caliper (could it be pre-69 911? or BMW?) and battery gone. Also noticed that six caliper had banjo fitting, mystery had flare fitting. Film at 11.
Posted by: rdauenhauer Aug 1 2005, 12:42 PM
Is the machining of the R. stock -4 piston bores out to 38 a reasonable alternitive given presumedly the -6 pistons are still available ? Eric does the application of your GT spacer kits make any differance in the equation? 
Posted by: Eric_Shea Aug 1 2005, 01:32 PM
We discussed (Mike Mueller and others in a previous thread) machinging the -4 but I'm afraid it's out of the question. You could take the bore out but you'd have no lip to attach the boot to and I'd be "very concerned" about the stability. Then there's pistons in general and that pesky inner piston assembly. 38mm pistons, or any part on these calipers for that matter, are unavailable. I suppose you could machine a new piston that would take the innerds of the -4 but... monumental task.
I don't think the V-Caliper would help much other than to situate it on a vented rotor. A V-Caliper, T-Fitting and an agressive pad would probably be enough to keep an A or S-Caliper happy but that's about where it would end.
Jim, an M-Caliper is an M-Caliper with or without the spacer. So... if it looks like the one with the spacer that you have on Ida, then it's an "early" 911 M-Caliper. Especially if it has a hub and a detachable rotor vs. a 914 rotor/hub. If it's fluid hole is on the bottom it's a Beemer.
Posted by: Porsche Rescue Aug 1 2005, 01:33 PM
Here is a front caliper on my conversion car. Anyone ID it?
Attached image(s)
Posted by: Porsche Rescue Aug 1 2005, 01:34 PM
and the right side
Attached image(s)
Posted by: Porsche Rescue Aug 1 2005, 01:39 PM
How about stock 4 caliper with one nipple? As you see it's on the top. Rotor is one piece as I guess it would have to be with 4 lugs (I forgot about that minor difference!)!
Posted by: Dan (Almaden Valley) Aug 1 2005, 03:42 PM
Eric,
Your quote:
"I'll have a 200-220hp -6 in my GT with S-Calipers up front and 911 M-Calipers in the rear (T-Fitting). I'm using the 911 handbrake assembly. Same basic setup that came on a 76 930 (with 240hp and a similar 7 & 8 x 15 wheel/tire package) "
So how did you get the 911 M calipers to fit on the rear? Will those fit on the rear with your modified 5 bolt control arms?
IF so are those M front Calipers or match M rears?
In my conversion I am not concerned about an "E" brake so I am just looking for a good fade resistant system for the track that will stop well and not require bleeding after every 30 minute session.
Years ago I had a 914-6 with a 2.7L RS motor and had JFZ 4 pistion calipers front and rear. The bias was always too much to the rear.
I want to avoid this problem this time around.
So what would be your preference among these choices?
M calipers front and 914 rears with ebrake.
M calipers front and 914 front calipers on the rear with no Ebrake.
A calipers on the front with M calipers on the rear with no ebrake
SC complete front and rear with no ebrake.
Complete Carrera fronts and rears with no ebrake.
What type of adapters or whatever would be required to make these work with the modified 5 bolt control arms.
I just want to do this one time.
I contacted Rich and he seems to think the SC calipers will just bolt right on to your control arm ears with 3 inch spacing.
Thanks
Posted by: Eric_Shea Aug 1 2005, 08:02 PM
Jim, those are M-Calipers. Early w/o the spacer. Great shape BTW. Addition: They could be early -4 calipers as well. In photos they're virtually identical. You have to have them side by side to see the small size diff as described in a previous post. Still reading, if it's on a 4-lug rotor it's a -4 caliper.
| QUOTE |
| So how did you get the 911 M calipers to fit on the rear? Will those fit on the rear with your modified 5 bolt control arms? IF so are those M front Calipers or match M rears? |
Sorry for the confusion. "Rear" M-Calipers. They are special for the rear of a 911 and they call them M-Calipers as well. The nose accomodates the hat (Mike, that's why the Front won't fit, the nose rubs on the hat). I'm not sure why they call them M-Calipers as well other than the fact that they may be of "Medium" duty requirements by the standards of the day. If Rich Herzog will weight in here, he had a list of L, M and S meanings... They are different in two outward appearance points, 1) the nose will fit a 911 rear rotor with the tall hat and 2) the fluid lines come in the sides not through the back as witnessed on the photos of Jim's "Front" M-Calipers. (914 calipers... sorry)
| QUOTE |
| So what would be your preference among these choices? 1. M calipers front and 914 rears with ebrake. 2. M calipers front and 914 front calipers on the rear with no Ebrake. 3. A calipers on the front with M calipers on the rear with no ebrake 4. SC complete front and rear with no ebrake. 5. Complete Carrera fronts and rears with no ebrake. |
I don't know the hp you're going to run so I'll number those and add it here:
1. Up to 140hp. If it's 140hp and a track car I would consider #3.
2. No. Too much rear brake. Porsche didn't have that much rear brake until #5 came along in 1984. You'd have issues again.
3. Up to 240-250hp. If it's 240hp and a track car I would consider #5.
4. See #3 (Same system)
5. Up to 300hp. If you're tracking with 300hp I might consider a Boxster Monoblock system.
All of those systems will fit a stock 914 control arm. If I recall (getting old) you were going to have a warmed over 2.0? 2056? I'd stick with #1, keep the handbrake and keep some pocket change. A V-Caliper might be nice just to keep things a bit cooler all around. I tracked my 911 with M-Calipers all day at Las Vegas Motor Speedway, never had fade and drove home that night. I recommend changing fluid after every race (ask Trekkor)
Posted by: Porsche Rescue Aug 1 2005, 08:23 PM
Eric, they must be 914-4 calipers. I recall that early 4's and later 4's were different. One had banjo, one did not. These are on a '74.
Posted by: Eric_Shea Aug 1 2005, 08:32 PM
Early 4's had one bleeder and Ribe head through bolts. Later 4's had dual bleeders and a machined nose assembly with 11mm hex head bolts. Different offset on the two as well.
Posted by: Porsche Rescue Aug 1 2005, 08:37 PM
Well, what do I have?
Posted by: Eric_Shea Aug 1 2005, 08:49 PM
Early -4 from looking at the bolts and bleeder and by the fact they're sitting on a 4-lug rotor.
Kinda narrows it down.
I know they're on a 74 but... it didn't leave the factory with those.
Which brings up another point; somthing must be up with the entire front suspension. The offset would be different, so that car "should" now have an early suspension. Maybe they swapped them out to make those wheels fit (no centering ring on an early rotor). These are on that black, flooded, motormeister "thing" that you replaced Ida for in your avatar aren't they?
Posted by: Porsche Rescue Aug 1 2005, 09:10 PM
That's the car. Doubt it would have anything to do with the wheels as they will fit centering hub. They are 7x15 Revolutions. Seems strange that someone would "backdate" the front suspension.
Posted by: Porsche Rescue Aug 1 2005, 09:25 PM
Answered my own question. Looked at PET and learned that 70-71 and some '72 4's had the banjo fitting connecting the hard line to the caliper. Later line was flare fitting. Therefore I have late, likely stock '74, caliper. Guess they don't all have 2 bleed nipples.
Posted by: Dan (Almaden Valley) Aug 1 2005, 10:14 PM
Eric,
What is a "V-caliper" you refer to for the rear? This combination with the M fronts sounds pretty "cool".
What rotor do you use with these and where can I find both?
Thanks for all your help.
I should begin looking for the front suspension and brakes next week and as soon as I find one I will contact you about the control arms witih stud length requirements and the bushings I want to use.
Once I decide about how long is the turn around time?
Posted by: ArtechnikA Aug 2 2005, 08:05 AM
| QUOTE (Eric_Shea @ Aug 1 2005, 10:02 PM) |
| ...If Rich Herzog will weight in here, he had a list of L, M and S meanings... |
those designations actually come from Porsche's original brake OEM ATE (Alfred TEves).
Leicht - 'Light'
Mitte - 'Medium'
Schwer - 'Heavy'
Posted by: Eric_Shea Aug 2 2005, 09:53 AM
Danke Rich!
| QUOTE |
| Therefore I have late, likely stock '74, caliper. Guess they don't all have 2 bleed nipples. |
That's hard to believe, especially on a 74 but... stranger things have happened. 72.5 I can see but... Anyhooo, I've seen "transition" calipers on the rear but none yet on the front. That's probably due to the volume of rears I do. A transition caliper is an early looking caliper with the later guts. I've run across a couple pair. I'd really be interested in the answer to this riddle. That 74 should have new style calipers...
Dan, your question limit is up.
Just kidding... http://www.914world.com/bbs2/index.php?act=ST&f=2&t=30994&hl= can be seen here. You would use a standard 911 rear vented rotor through 83. Turn around time depends on cores in stock. I've had a run on them in the last week so I'm getting low. Also, with specialty studs, I like to send the hub to the machinest "with" the stud so we get a perfect fit. Plan on a total of two weeks. The machinest can take a week. If you want them for racing then plan on the open nuts and 72mm Verbus studs.
Posted by: Root_Werks Aug 2 2005, 09:59 AM
This is a good thread full of info. I like the reading! Thanks everyone for all the input.
Posted by: Porsche Rescue Aug 2 2005, 10:09 AM
Eric, if late '72 (transition) were "one nipple", it is quite possible mine were from a commercial rebuilder and were rebuilt '72 cores installed on a '74. Given their fairly "fresh" look they probably were rebuilt somewhat recently.
Posted by: Eric_Shea Aug 2 2005, 01:47 PM
| QUOTE |
| Mitte - 'Medium' |
Middle?
Posted by: Eric_Shea Aug 2 2005, 01:49 PM
Jim,
That's what I was thinking too. There's no way a caliper would look that good today so it must be a rebuild. Let me know if you dig in and find otherwise.
Thanks Dan.
Posted by: ArtechnikA Aug 2 2005, 01:56 PM
| QUOTE (Eric_Shea @ Aug 2 2005, 03:47 PM) | ||
|
the words are the same either way...
Posted by: Eric_Shea Aug 2 2005, 02:28 PM
So the 914 is a "medium" motor car... we knew that
Posted by: Eddie914 Aug 2 2005, 05:25 PM
What are the dimensions of Carrera rotors?
Are there any larger rotors that car be bolted directly to the back of the hub?
Will 968 rotors fit over the hub?
Thanks Eddie
Posted by: johnmhudson111 Aug 2 2005, 07:11 PM
| QUOTE (Mueller @ Aug 1 2005, 10:14 AM) |
| yes, however, you lose your e-brake.... |
Here is a question, how difficult would it be to fab up a bracket to relocate the /4 rear caplier so that it would be used as an e-brake only? On the surface it seems to be a workable solution. The only issue I can see is using/getting the correct spacers to widen the caplier for the thicker rotors. You guys know better than I, what do you think?
Posted by: ArtechnikA Aug 2 2005, 07:52 PM
it is the application of the service brake that keeps the pads adjusted.
i don't think shrouding the disk with another caliper is a great idea, but i have seen this kind of thing done before -- but it was with a really teeny caliper and a BIG disk.
Posted by: Eric_Shea Aug 3 2005, 10:24 PM
| QUOTE |
| What are the dimensions of Carrera rotors? |
24mm
I really don't have any experience with any other rotors.
Posted by: johnmhudson111 Aug 4 2005, 07:00 AM
| QUOTE (ArtechnikA @ Aug 2 2005, 08:52 PM) |
| it is the application of the service brake that keeps the pads adjusted. i don't think shrouding the disk with another caliper is a great idea, but i have seen this kind of thing done before -- but it was with a really teeny caliper and a BIG disk. |
Is the concern you have with this method based on the impact the 2nd caplier would have on the rotors ability to disapate heat?
It seems like it would be pretty simple to fab up a bracket to make this work but again, you guys have more experience in this department than I do.
Posted by: ArtechnikA Aug 4 2005, 07:09 AM
there are two concerns i stated.
1) the brake will not self-adjust. in theory, the pad should experience 'no' wear used as a parking brake; i know the dedicated parking brake in my 911 has received no adjustment in at least 2 years and doesn't seem to need any, so perhaps this is not a serious concern.
2) you reduce (by a fairly significant amount) the surface area of the disk exposed to free-stream air for cooling.
is it bad enough to worry about? no one knows. i'd invest in some Tempilac heat-indicating paint and use *real* good brake fluid during the testing phase if you decide to go this route.
3) you've also increased unsprung weight by a nontrivial amount, but that may not be a horrible thing on a street car either.
frankly, i think i like the small inboard disk and caliper concept a lot better.
so i'm not saying it won't work, or it can't work. IMO the disadvantages outweigh the gains, but there is all kinds of room for experimentation and tinkering. so don't let me talk you out of it if you feel it's worth trying. just please be careful.
Posted by: davep Aug 4 2005, 10:06 AM
I saw an interesting parking brake on a 934. On the typical huge rear caliper were a pair of 'wings'. These wings pivoted off the bottom of the caliper, and carried a few square inches of friction material each. The tips of the wings were tied by the parking brake cable, and there was probably a spring in there to spread the wings when the brake was off. This car came fitted like that from the factory, raced at Le Mans, was in the Matsuda collection and is still factory original.
Posted by: Eric_Shea Aug 4 2005, 01:37 PM
I say go with the strings and wings!
Posted by: ein 6er Aug 4 2005, 05:13 PM
| QUOTE (davep @ Aug 4 2005, 08:06 AM) |
| I saw an interesting parking brake on a 934. On the typical huge rear caliper were a pair of 'wings'. These wings pivoted off the bottom of the caliper, and carried a few square inches of friction material each. The tips of the wings were tied by the parking brake cable, and there was probably a spring in there to spread the wings when the brake was off. This car came fitted like that from the factory, raced at Le Mans, was in the Matsuda collection and is still factory original. |
i believe they were 917 calipers. http://www.pbase.com/9146gt/gt_alloy_calipers_917_brakes are some pics on armando's site.
Posted by: ein 6er Aug 4 2005, 06:36 PM
http://www.pbase.com/9146gt/930_turbo_brakes_911rsr_parking_brake_mechanism is a link to the mechanism.
Posted by: Eric_Shea Aug 7 2005, 02:45 PM
Those look "fairly" easy to mfg.
Any of you machinest (Mueller) types care to take a stab? They could hang off a special spacer made for the M or Carrera caliper
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