What Alfa Romeo alloy caliper (from what model car) is suitable to replace 3"
front calipers ?
AND...is it suitable for use on the rear of a 914 with 911 vented rotors ? provided
911 emergency brakes are adapted.
TIA

GTV6 I believe. You can usually find them on eBay. I don’t know it they will fit rear. Same mounting and spacing as an M caliper so if a front M caliper will fit in the rear then it should work but it doesn’t sound quite kosher to me.

Yes GTV6. I have a set on the back of my 914-6. They work quite well.

Matt

That's good to hear Matt.
Have you worked out the emergency brake yet ?
If so...do tell !

The Suby conversion car I just sold had a pair of tangerine racing e-brake adapters installed. They are used in conjunction with 911 e-brakes. It’s a super clean install that looks factory. I would do it again.

I also used the tangerine kit with early 911 emergency brake. It passed inspection but they could use some adjustment.
My front calipers are Boxster and the rear Alfa. Lets just say it stops fast...
Matt

A 48mm piston is way too much for the rear of a 914. Tge 4 cylinders used 33mm, the 914-6 a 38mm.

I was hoping to find a light weight caliper suitable for the rear but your point is well
taken.
I do intend to adapt 911 Ebrakes.
What caliper is suitable for the rear with vented rotors, a 19mm or 23mm master
and 911S alloy front calipers ?

911M caliper. S front & M rear were factory spec for the mid 70’s turbo. That was a heavy car.

48mm to big? How about with adjustable proportioning valve?

Matt

I imagine that would work but then you’re spending a couple hundred dollars extra just to loose a couple pounds. Not a bad thing but an expensive way to loose weight. It’s always nice to build around the bias that the Porsche engineers figured out.

Every proportioning valve I've messed with REDUCES pressure and flow to the rear.

The valves do not have the ability to increase pressure or flow to anything.

You could put a real proportioning valve in backwards and reduce pressure to the fronts but that sounds like a poor decision IMO.

Balancing the caliper piston sizes is the best way to gross balance a system and the 48mm pistons appear to be too large for application on the rear.

Found this in the classics forum and it's appropriate for this thread.

http://www.914world.com/bbs2/index.php?showtopic=55559


One nice thing regarding the original relief valve is that it doesn't care about balance at all. It just stops all pressures above 525 from reaching the rear calipers.

It's adjustable as well. Testing and adjusting it might be sketchy...

It's too bad PatMC is right.
Looked like a possible candidate for the rears.
Still looks like these could be used on the front, however.
They would be the same as the BMW calipers, just made out of aluminum.

Final thought. The ratio of front to rear that Porsche used is 42/33 4 cylinder and 48/38 on the six cylinders. On a 4 cylinder the size of the rears is 78.5% of the fronts and on the six it's 79.1%.

Staying close to this 80% ratio is the way to go in my book.
Most cars use a front to back ratio of 75-80% so Porsche was "normal" in how they set up brake bias.

Proper fronts for a 914 with 48mm rear pistons would be nearly 60mm on the fronts and you'd need a much larger master.

Good info. So what should I do? I have Boxster fronts and the Alfa rears? What would be the ideal front and brakes set up for a track/road car?
Matt

How big are the Boxster fronts or what size are Boxster rears. Figure out the ratios and see if you are in the ballpark. Ratio might be better than S front, Alfa rear.

I just bought a set of front and rear Boxster calipers. I figured it would make things easy(er)

I have base Boxster front calipers. I will look into the size of them. I have many other projects to do on the car first.
I have used the brakes very hard and never had the rear wheels lock.

Matt

Hey, if it works, it works.

@rgalla9146

They were used on 85-86 GTV-6 and the model that rep kn aced it in 87.

I installed SC's on the front with 48mm pistons and moved the old fronts to the rear 42mm. Works great. Four years no lock ups with auto cross and hard street driving also with a T replacing Proportioning valve. just no hand brake (OK with Me). Best, Mark

You need to look at surface area, not diameter....

42mm = 2.14sq in
33mm = 1.32 sq in

48mm = 2.8 sq in
38mm = 1.75 sq in.

Boxster frt( 36/40mm pistons) = 3.53
Boxster rr (28/30 pistons) = 2.0


Now you can calc your ratios...but those are just hydraulic ratios.

Now you need to determine the effective radius in each of your examples (spindle centerline to centerpoint of brake pad friction puck) and take that into acct.

Very few vehicles have anywhere near as much rear brake as your 75-80% figure suggests.

I think you'll likely find that putting the stock brakes in excellent working order with quality pads will result in excellent performance and fewer headaches. The rear calipers don't weigh much...5 or 6lbs each. The fronts are a bit heavier but not much.

The Alfa calipers on the front are a neat replacement for M’s because not only are they half the weight, they have a large pad. They mate up great with a 914-6 rear caliper.
If you already have M’s on the front, it’s just the cost of the calipers and some hardware.

If you are starting out from scratch, these big brake options are expensive. Remember, brakes really only see mass x velocity. Horsepower doesn’t really come into the equation.
That being said, my cars are big model toys to me so I built them the way that makes me happy. Cool looking brakes are one of those items that I just want what I want.

Alfa like this?

I was an early adopter. Eric Shea suggested them and I obviously bit. My rears are the alloy collaborations between 914Rubber and PMB. They are unobtanium now.

They are on eBay and other sites. Now granted, they aren't cheap to rebuild, especially if you want the polished silver finish but similar to 911S calipers, that's just the way it is.

You can also buy new reproductions.

Yes.
Please fill in the blanks... What front calipers and master cylinder ? prop valve ?
How do they work ?
Fingers crossed.

I just re-read your reply and realize your rear calipers are the alloy copies of original 6 rears.

Hi Rory,

Is this setup for the white GT ?

On my 71 914 I use to run a set of 944 turbo on the front and 911 M rears (no e-brakes).
I used a Mercedes 23 mm master cylinder with a T fitting (yeah yeah I know).
I never had an issue with the tires locking up and I drove it like I stole it.

I now have a full set of Boxster calipers w'/ RJ mounts, T fitting, and 23 mm master going into my 6. Using early 911 e-brakes setup. I went with a cam lever bracket setup vs a short cable. Seams to work but time will tell.

My brothers GT has S aluminum calipers up front, PMB mod GT 6 calipers at the rear, T fitting, and a 19 mm master. The pedal feels spongy to me but my brother is ok with it.

Hey Luke
I have S alloy calipers on the front and 914 6 rear calipers (widened 10mm for
vented 911 rotors) on the rear.
With the 6 rear calipers the ebrake cables rub against the exhaust.
This is especially true with headers.
To remedy this I'm going to install 911 ebrakes... I need to find suitable rear calipers.
I do have a full set of 944 turbo calipers and a 23mm MB master.
How did the 944 Turbo calipers mount to the 3 1/2" struts ... and can they mount to the 914 trailing arms ?
As you probably know I'm running 16" Fuchs so no clearance issues.

@rgalla9146 What can I do to help you brother, pictures of the bottom of my 6 and a
picture of the vented rear 914-6 caliper. My cables do not touch the Heat Exchangers. I did have eric set up a rear trailing arm with tube reinforcements and Elephant bushing for my V8 car that we changed direction on That was going to use Boxster non S rear with Rich Johnston adapters and vented disks

Best Bob B

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Took my vented rears off the race car 20 years back when I verified the temps with heat paint…. Not needed
Just extra weight


A really big motor on the track…. Higher top speeds.. Maybe..
But got the car down to 1810lbs by cutting unnecessary weight
And they were not necessary

That is some good experience and wisdom, thank you.
Matt

Hey Bob
Tell me about the Boxter rears and the Rick Johnson adapters.
Do you know the diameter of the Boxter pistons ?
I can't clearly see path of the ebrake cables in you pics.
In my car the cables will be melted by either HE's or headers unless I torture the
the path away from the trailing arm bracket
I have S alloys (48mm)in the front.
I need ~38mm calipers for the rear.
This nearly follows the original ratio front to rear.
The 911 ebrake install is to remedy the cable issue.
What is the finish on your HE's ?
Your car is beautiful.
Rory

Hey Bob
Tell me about the Boxter rears and the Rick Johnson adapters.
Do you know the diameter of the Boxter pistons ?
I can't clearly see path of the ebrake cables in you pics.
In my car the cables will be melted by either HE's or headers unless I torture the
the path away from the trailing arm bracket
I have S alloys (48mm)in the front.
I need ~38mm calipers for the rear.
This nearly follows the original ratio front to rear.
The 911 ebrake install is to remedy the cable issue.
What is the finish on your HE's ?
Your car is beautiful.
Rory
[/quote]

Just some info from the web. The real answer is going to come from Eric or Larry at PMB but they are going to be super busy with Rensport.
I believe that @Sir Andy has Boxster’s all around on his Red 6. My muffler is polished SS custom 2 in 2 out and the Heat Exchangers have bright Ceramic finish.




Old posting from: Luke M
Aug 19 2013, 09:05 AM

I plan to run the standard Boxster calipers all around my car. The car will see street, autox, & some track time so I wanted more braking power. I got some of my parts from Rich (a914guy) check his ad in the members vendor section. I haven't installed the brake setup and have no answer on how they work. The all mighty Sir Andy also has the same Boxster setup on his 3.6 powered 914. He may be a good person to ask on how they work. Yes, you lose the e-brake but I installed a 911 e-brake setup on my 914 control arms. It's not a 5 minute job but it can be done. If I don't like the Boxster setup, I have a backup set of early 911 aluminum S & 914-6 rear calipers to try out.

-----Just general notes from web: Not me---
Gen2 Cayman & Cayman S Brake Sizes
Gen2 Cayman-
Front: rotor dia 298 mm, thickness 24 mm, piston dias 40 & 36 mm
Rear: rotor dia 299 mm, thickness 20 mm, piston dias 30 & 28 mm.

Gen2 Cayman S-
Front: rotor dia 318 mm, thickness 28 mm, piston dias 40 & 36 mm
Rear: rotor dia 299 mm, thickness 24 mm, piston dias 30 & 28 mm.

Non'S':
F Disc 298mm, Pistons in Calipers 2x40,2x36 mm , pad area 216 cm^2
R Disc 292mm, Pistons in Calipers 2x30,2x28 mm , pad area 196 cm^2

"S":
F Disc 319mm, Pistons in Calipers 2x40,2x36 mm, pad area 254 cm^2
R Disc 299mm, Pistons in Calipers 2x30,2x28 mm, pad area 196 cm^2

When I put 16" wheels on my 99, I couldn't believe how close the clearance was to the base brakes, so the bigger S calipers would definitely not fit with the OEM 16" wheels.. Not Bob B

-----------------------------------

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Best Bob B

Hi Rory,

On the front the 944 calipers would need to have the mounting ears modified/machined to fit a 3 1/2'' strut mount. VCI use to do the mods but think it's out of business now. Lots of info if you google VCI Porsche brakes. On the rears no clue as I ran the 911 M rear calipers/rotors from a 911. I don't think there's enough material on the caliper mounting ears to make the calipers fit the 3'' rear mounts. I can tell you that the best way I found to get big brakes was the Boxster calipers all the way around. Get the adapters from RJ they work with the 911 carrera rotors up front and the standard 911 rear rotors out back. Get a set of early ( 69-71 ) e-brake hardware and install on the 914 arms. If I had to do it again I'd use the Tangerine kit as well. Just need to make sure the calipers are positioned properly (Lead piston position). As far as the e-brake cables go, I didn't have any issues w my brothers car hitting the exhaust. I guess I better go stick my head under his car and double check to make sure that's the case.


Check Andy's thread here and you'll see my setup :

http://www.914world.com/bbs2/index.php?showtopic=170890

Hi Rory

This is what I think are the fronts with the RJ adapters. Not sure what is different in size, but you can get an idea of the piston size. I went over this with Eric S in Jan or this year.

I have a lot of pictures. I have a set of rear calipers from my 86 Carrera (that car is now with Dax in Belgium with PMB rebuilt calipers on it) that need rebuilding that you can have for free. You just pay the shipping. You can have the fronts as well.

Best Bob B


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i have 944T brembo's front and rear which were fitted by PO, I believe the rears are mounted by welding up the old threaded holes and repositioning them,the struts have machined offset inserts threaded into them which as an engineer I think is a clever solution.
All calipers have special 1mm spacer washers that fit between mounting ears I presume these are to centre the calipers to disks , running ER 5mm "shim'' spacers @ the front with 7x16 Fuchs .
PO added new 19mm master cylinder and the whole lot works very well together ,only solution in our country as adaptors are illegal. .

Yes. Alfa front. Which are available but not in the beauty contest form @Eric_Shea made them for me. Rears are the alloy copies of the 914-6 rear calipers. You can probably get Eric to build some of the Alfa brakes for you. I don’t think anyone could ever get him to make more alloy rear six calipers unless they ordered 100 sets.
It’s overkill, but if you’ve followed how I built my car, overkill was the point.

Good update on rear calipers.
I found these among my random collection but have no idea what they are from.
Could be VW, Audi, 356, 911 or ?
They're ATEs with 38mm pistons and are suitable for vented rotors. The spacers in
them are as manufactured. These are a good match for alloy S fronts.
They mount on our trailing arms and with a fat washer are near perfectly centered.
They are left and right with the bleeder at the top and the hard plumbing to the
bottom. They take 60mm pads, same as 914 6 rears.
I guess no alloy rears for me.
Anyone know what they're from ?

Next mystery.
I've had these 911(what year ?) 944 (?) ebrake parts for years thinking they might come in handy.
Thing is, they seem different from any others that I've seen used in a 914 conversion.
The shoes are wider and the retainers are flat spring steel. See photos.
The shoes are wider than the contact area of my 911 vented rotors so
~1/8" of the shoe hangs outside the drum, so not compatible.
The intesting part of these is the stop for the bottom of the shoes is incorporated
in the backing plate. Maybe this feature can be added to the more compatible
911 ebrake parts.
What years of 911 parts are best for this conversion ?

@MB911 Ben did the conversion recently and needed some different parts to make it work. I’m sure he’ll chime in.

I send my “what’s this caliper” questions to Eric Shea.

1970-73
Matt

Those brake shoes look like the right parts. The center stop on lower portion needs to be welded to rear control arm.
Matt

Standard 911 rears from 69-83. The early ones had a machined spacer, later went a cast spacer.

Well mine was a clusterF$&@. I would not suggest to anyone. It works fine but what a PIA. You need 69-73 parts and the best part is you get to modify the bracket out of them. Had to have a machinest machine down the brake shoes. In the end I was super irritated with the process. Parts are very hard to find

I gave you the cores. I wonder if they were the wrong year to work with or 944 brakes or something. When Scott did mine on the Suby car, he didn't have the issues. I don't know what year brakes I gave him.

I've got the caliper part pf the project covered. Years ago I parted out
an '83 SC. That's where the mystery calipers (and my engine) came from. Early in
this thread Mark Epstein suggested 911 rears might be the ticket and to
ask Eric Shea... Doh !
I think the 911 ebrake parts are difficult to get because breakers want to sell the
trailing arms as a complete assembly.
That's my next challenge.

Am I going to have to take my brakes apart and take pictures? I have the Alfa calipers and the early emergency brakes setup with tangerine racing adapter kit.
@rgalla9146

Matt

Hey Matt
NO,NO,NO ! I'm making good progress and love the process.
Working out issues like this is therapeutic. I like to solve a problem step by step.
Rory

Mark Calipers, stubs and hubs were awesome. The rest was a major learning curve with a bunch of trial and fitting then machining, then fitting, then matching. None of that was your fault. The problem is not many of these parts have actual part numbers on them so you going off pictures and descriptions.

Click to view attachment

Here is my set up done.

Hi Rory,

So here's the issues that I ran into while doing this mod. You need to make sure you get the correct e-brake shoes for the early (70-73) e-brake backing plates. Yes, there's a few different ones out there. I purchased two new sets and both where wrong. The e-brake shoes are too long so they do not fit under the SC/early 911 vented rotors. I'll have to find the part # which worked and post it here for you. I believe I got the correct set from Stoddard. You can buy just the backing plates used and the new hardware kit from PP or Stoddard. You'll have to grind down the control arm mounting plate bosses a little so the backing plates fits. I also installed a tube through the control arm so I can remove the Boxster caliper pad pin. If you look at Andy's thread he modified the pin to install/remove it. Then you'll need to add a pad plate(it's what I call it) basically a 90 degree angle iron with a hole in the middle of it. It's used to support the e-brake shoes at one end. The Tangerines kit has those pieces included (pic attached of that). Then you'll need to relocate the factory E-brake cable bracket on the control arm. You'll cut it off and move it to a more straight/inline position to attach to the new e-brake setup. I'll post pics/info on here as I find them. You've got my # if you need to give me a call on it.

Here's the e-brake pad and hardware info. The hardware is sold as a complete set. Take a look at the shoes. Pay real close attention to the angle at the upper end. The new pad will not work and needs to be like the old pad. The new pads are a little large in OD once installed which makes installing the rotor impossible. That was the case at my end. Spoke with a guy at Stoddard and he knew exactly what I was talking about. So this must be an issue with some of the pads being made. This was about 6 months ago so not sure if the issue has been resolved with the manufacturer.