I know in the past everyone has discussed using M calipers on the front with stock 914-4 rears along with a T fitting in place of proportioning valve.

What if you were to use the M calipers and 914-4 fronts on the rear utilizing the proportioning valve. would this negate enough of the rear bias with the larger 914-4 front pistons to give good braking? Possibly utilizing a milder rear pad as well with a very aggressive front pad?

What do you think....and no I don't care about the E brake.

Thanks

M pistons and 914 pistons are almost identical in size iirc*......

statement subject to verification*

I agree Aaron. On the fronts. I am talking about moving the 914-4 fronts to the rear. The 914-4 fronts have considerably larger pistons than the rear 914-4's, IIRC. That is why I am suggesting that combination with the P valve.

but.... look at the ratio. lets say 914 fronts were X diameter Pistons, and the reats were X - 15 size. this RATIO ustilized the p valve.....

now with M's and 914 Fronts, you have
X in rear and X up front.....

not the same ratio, so maybe a more restricitve P valve

I see what you are saying Aaron.


Maybe I'll need to use an adjustable p valve?
My 914-6 had JFZ 4 piston calipers front and rear with the stock Pvalve.
Worked well with a less aggressive rear pad.

and like you mentioned, you can play with pad compunds, etc... rear venting clearances.....

try an adjustable P valve....

dude... the JFZ's were the shizzle...
i fondled a set before. very coolstuff

Yah, those JFZs were cool. and talk about stopping....Limiting factor was the tires not the brakes.

But that car had a much higher speed and acceleration curve than my new
4 banger. Now it is back to momentum...don't use the brakes near as much.
I am using the bigger calipers and vented front rotors because this car will probably be used to train my Son and Daughter all about AX and DE. I want them to have plenty of safety margin once they go onto the track.
Not to mention as beginners they will make the rookie mistake of overbraking everywhere

You can play around with some of the M calipers. There is quite a range actually. The 914/4 front is 42mm pistons, and the early fronts are very close to the 911 rear caliper. The 911 early rear and the 914/6 rear are both 38mm pistons. The late 911 rear is (I think the early 914/4 front) and has the 42mm pistons. Not sure if the late 914/4 front will fit on the rear without a spacing issue. Of course the 914/4 rear has the 33mm pistons. With a bit of work you could also use the 911 / 914/6 front on the rear with 48mm pistons.

So you have the range of 33mm to 48mm, and you will surely require something to limit the braking power of the rear.

Thanks Dave

QUOTE

With a bit of work you could also use the 911 / 914/6 front on the rear with 48mm pistons.

That would be a great deal of work. The 911/914-6 front (M-Caliper) has a nose that is too large and it hits the hat on a rear rotor (probably cause of that 48mm piston).

Yes... you could use the M-Caliper up front and the 914 front in the rear with an adjustable p-valve. That's still a lot of rear brake for the application.

The 'late 911 rear' Dave mentions with that 42mm piston size didn't come around until the 1984 model year and it's the first time the 911 began to use a proportioning valve.

Refresh my memory on your HP and your tire size & compound.

E.

Eric,
thanks for the reply.

~100+HP
Dot "R" 205 tires.

QUOTE

~100+HP Dot "R" 205 tires.

I think you're spot on then (this is for racing?). Here would be my choices. I think I'd go 'A' or 'B' and keep a handbrake (I know, you don't care about it).

System A:
911 M-Strut with vented rotors (or Mueller hub if you're 4-lug)
M-Caliper
Porterfields
T-Fitting
Stock Rear on a Solid rotor
Porterfields

System B:
911 M-Strut with vented rotors (or Mueller hub if you're 4-lug)
M-Caliper
Porterfields
T-Fitting
V-Caliper Rear with Vented rotor
Porterfields

System C:
911 M-Strut with vented rotors (or Mueller hub if you're 4-lug)
M-Caliper
Porterfields
T-Fitting
Cockpit adjustable Valve
Front 914 Rear on a Solid rotor
Porterfields

i have setup A, M's with Tee, porterfield R4S pads and itll stand on the nose....

Eric, Thanks again for your replies.
I am probably overthinking this whole thing.
I have the magic billet 4 lug hubs. I have a set a m calipers for the front and also SC rotors.
I will plan on using option A since that is what I had been planing on anyway.
Just got to thinking the other day about using the fronts on the rear.
I guess I will have a nice set of front calipers for sale soon.

I was planing on using porterfields so that fits right in with my thinking.

This will be a 95% track car that will be driven only to the occasional AX.
Flat towing to TT/DEs.

No problemo

The only other thing I would suggest (in your 95% racing situation) is 'get some air to them'. There's a bunch of options around but the simple and easy kit that attaches to the a-arm with the hose to the backplate is pretty damn good.

Wise choice.

Actually along the cooling theme. I am going to fab up some scoops to reside in the area where the fog lights used to be. I will then run some hose to the back sides of the calipers and rotors.
Although with the 4 banger momentum is the name of the game so the brakes aren't going to get too hot anyway