robt964

Hi guys,
I know a few of you have converted your C2 964 over to use the 993 MC and servo and the process is well covered.

My question is, is it worth while?

With my MC now 25+ years old I have no idea how much longer it will last. A replacement is stupidly expensive where-as the 993 item is not. In the spirit of pre-emptive maintenance, if you're going in there to swap it out, why not convert to the 993 item?

I have std 964 4 pot calipers up front and 993 C4 rear caliper on the rear with the appropriate PV valve. (car still feels under braked on the rear axle)

What are the physical pros/cons of this?
Anybody know the MC bore sizes of each?
Does the 993 servo offer greater mechanical advantage than the 964 servo?

Thanks
Rob

ras62

I think it gives a slightly higher boost ratio and is a tight fit. New mounting brackets needed and I think the hydraulic fitting sizes are different m10/m12 iirc.

http://forums.pelicanparts.com/porsc...nalysis-7.html

porsche mania

Not sure if it's worth it with the calipers you have. I've got 996turbo fronts and the old fronts on the back of mine and while it worked with the standard 19mm mastercylinder the pedal travel was excessive, surprisingly the pedal feel and modulation is greatly improved on mine even though the booster is bigger! It is a tight fit and the bracket had to be modified with the rs front roll bar but apparently go straight on with the standard arb.

porsche mania

The 993 mc is 23.8 mm by the way

Bill Verburg

964C2 booster is 8" w/ 3x boost factor, 964 C4 has 4.8x boost, 993 is 9" 3.15x boost

the feel at the pedal is higher and harder w/ the 993 booster, most consider this to be desirable.

w/ oe 964 front and 993 rear you have a nearly ideal brake bias for a lowered stiff car w/ effective lsd
bias below p/v knee/bias above p/v knee
964 4/4 is 1.734/3.210
964 4/2 is 1.508/2.793
964 4/993 4 is 1.42/ 2.629

911 Carrera 2.7 1.491

FormulaRX

Don't mean to hijack the thread but if I install 996 turbo front calipers and move my stock fronts to the rear, do i need to upgrade the MC? I have a C4 and I heard the stock MC is adequately large enough for big brake upgrades

Steve Weiner-Rennsport Systems

I would certainly upgrade the MC to the 993 one with those calipers.

540964

Do it you will be happy you did.

FormulaRX

Will a 993 C2 MC work in a 964 C4? Will it affect the abs/PDAS in anyway? Straight swap?

Vandit

I don't know how it works w/ the 993 generation, but the 964 C2 vs C4 braking system are totally different animals.

Bill Verburg

Moving fronts to rear creates 2 problems, both are potentially major issues
1) bias approaches 1, you have way to much rear and the rears will tend to lock first.
2) front 964 rotor want 26-28mm thick rotors, 26mm is the minimum, rear 964 rotors are 24mm when new.

Bill Verburg

993 C2 is a vacuum boosted m/c, it cannot be used in the 964 electro-hydraulic boost system.

Not to worry though as 964 C4 comes w/ a stock 23.8mm m/c, same size as that used on the 993C2. An upgrade here would be to use the 964 RS/t mc which is 25.4mm

porsche mania

After running this setup for a while I'd agree with you regarding the rear bias, it has cpught me out on the track before when trail braking into turns! I'm already on the lookout for a set of 993 c2 4 pots. Regarding the disc thickness issues my pads are changed at 50% wear so considered it a mute point.

FeralComprehension

What's the subjective change in feel with a move like this?

Bill Verburg

The brake pedal is a little higher and harder and are a little easier to modulate