perrew

Very nice writeup!! Im doing the m/c swap, but is it really necessary to change to the 993 brake booster?
Tks P

KaiB

nope...

RSAErick

Interesting... I had come to the conclusion (assumption?) that the 993 booster was the required mate to the 993 master cylinder. It appeared that the 964 'spring assembly' was located on the m/c; whereas the 993 'spring assembly' resides in the booster. Here is a pic of the external differences (Left = 964; Right = 993):



I do not have a good picture of the internal portion of each booster, so please tell me if my logic (or lack thereof) has failed me...

Thanks.

KaiB

Erick, I glibly said nope due to the fact that I run a big brake system without either a M/C or a booster swap...

I actually don't know for a fact that I'm correct - and if I'm not, Bill V. will dang sure let us know...tehe. I'm curious, but I do remember discussing this with Weiner and it sure seemed that one could indeed run the 993M/C without the expensive booster swap.

993PET

I did both. I don't think the 993 MC fits with the 964 booster.

JF

Hsianers

Erick

Thank you for the most informative write up... I am in the midst of rebuilding a 964T 3.3 and was looking to go with Big Reds as the costs of overhauling the existing 20 year old calipers appeared to be fairly costly.. Will need to reconsider next steps based on this post...

RSAErick

I'm glad that you found it helpful. Good luck with your project!

ACSGP

Bit of a dumb question Erick, but does the RSA run the C2 brake set-up (vacuum assisted) or the C4 set-up (hydraulic)?

If you're on the C2 set-up, did you consider using the hydraulic system, or was cost too prohibitive? I know quite a few people have bought a C4, converted it into a C2, but retained the hydraulic system.

RSAErick

It's the same brake system as C2. It would be nice to have the C4 brake system, but I went with the easier and cheaper option. I don't know exactly what all would be involved with going from the vacuum to hydraulic brake system. Are you considering that?

Vandit

Rennlist & Pelicanparts member perelet is currently in the process of converting his C2 to hydraulic boost. Knowing him, it's likely he is documenting the heck out of that conversion.

oldtimer

Hi Erick , thanks for the write up. My 964C2 has had most of the modifications you describe done by previous owner . Looking at the bills , here's the list of bits

993Turbo big red front calipers
964RS rear calipers
993GT2 front uprights
993GT2 tie rods
993 master cylinder
'993 master cylinder pipe kit to 964'

There is no mention of the 993 vacuum booster , so assume the 964 original is still in place.

When I first got the car , the brake lights would come on even if brake pedal not depressed - not always , but when friends followed me they would see it happening intermittently . My independent Porsche specialist made adjustment at the pedal box to cure this , however......

he noticed that when the engine was started , the brake pedal would depress itself slightly - a movement of about 5mm at the pedal .

we did not think any more about this until recently when i found it really hard to manually push the car along ( engine off ) when queuing in the pitlane to go out on circuit.

on further examination it looks like with the engine running the vacuum booster is putting the brakes on slightly, visible evidence is the brake pedal movement , and there is no spring acting to resist this......this also seems to appear as a drag on the brakes even when engine is switched off unless the brake pedal is manually put back to 'off' position.

So looking at the differences between 993 m/c and 964 m/c , maybe using the 964 booster results in a 'pull' on the brake pedal equivalent to a push on the brakes...and the cure is to fit the 993 booster...????

perelet

Problem is that 993 has return spring inside booster while 964 has return spring on MC. You should use MC/booster as pair. 993 MC will bolt in to 964 booster, but you lose return spring.

See pic of both earlier on in this thread.

Oleg

Paul284pt

Hi Erick,

Just been having another look at your great info as I'm about to complete my brake system.

I have already fitted 964 3.6 Turbo callipers front (with adapters and turbo discs) and the matching rear 3.6T callipers (with 968CS M030 discs).

I am about to follow you and fit a new 993 master cylinder, 993 vacuum booster, master cylinder mounting bracket, gasket and bias valve. Finally, new brake lines/fittings.

Question: Is it possible to keep my existing brake reservoir?

Thanks in advance,
Paul

RSAErick

I believe that this should be fine. I kept the 964 reservoir, and have not had any issues with the 993 master cylinder and booster under hard track use. In fact, it has been rock solid with no fade whatsoever. I do not know the exact difference in volume between the 964 3.6T/964T and 993TT/993C2 calipers; however, I don't expect this would change the equation much, if at all.

Enjoy!

Paul284pt

Hi Erick,

Thanks very much for your prompt response. That's great we'll get on with it!

If yopu don't mind may I borrow a couple of your photos from this thread to help with the installation?

All the best,
Paul