Brakes - C2 vs C4 vs RS vs Turbo?..

smallspeed · Aug 4, 2007

Im looking at the brakes on my car; one of the rear calipers is sticking a bit and could do with a re furb, however Im considering upgrading the rear calipers then fixing what I have and selling on to re coup some of the expense..

I think (put me right if Im way off track) that the C4 and RS had the same front calipers as the C2, but the rears are larger 4 pot calipers (RS got the same rear calipers as C4)..

Also the master cylinders are different; I think the C4 master cylinder is slightly larger (prob to cope with larger piston vol from bigger rear calipers). The RS master cylinder is larger again as I understand it but not sure why, poss same as the turbo?..

I also believe one of the other main performance advantage between C4, Turbo and RS vs C2 is hydraulically boosted brakes vs vacuum..

So if I were to upgrade my rear calipers as stage 1 of a future upgrade program (ie eventually going to big blacks/reds on front with x-drilled RS disks, C4 rear calipers with std disks) what should I do?..

Im thinking I should upgrade to C4 rear calipers and the C4 or Turbo/RS master cylinder. My concern with this is whether the C4 master cylinder is big enough to cope with big reds/blacks when I get around to upgrading the fronts? hopefully someone with a C4 and big reds can comment [

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My second thought is to replace the vacuum assistance with the hydraulic power assistance but Im not sure whether this is feasable? I dont want to get into replacing lots of big expensive parts as a knock on effect of this (ie ABS pump, ABS ECU, etc..) Is there really that much benefit in doing this change and would it be worth the effort/cost at this stage in preperation for the front end upgrade..

Hope someone can comment on my assumptions and provide some insight into my planned upgrades!..

Ben

Laurence Gibbs · Aug 4, 2007

depends on what car your fitting them to and what model year. The RS had the 3.3 turbo front calipers and disks(bigger than the standard C2 and C4) and 4 pot rear calipers derived from the carrera cup car. Later post 91' C2 cars have 4pot rears also, earlier cars got 2 pot rears. The C4 and RS use a high pressure electric servo C2 uses vacuam servo. Next stage up is the "big reds" front calpers from the later 993 turbo these are bigger than the 3.3 turbo calipers and use larger disks. However unless your tracking the car and using the brakes real hard the big reds are probably overkill for a road car. Bigger disks can also upset the abs too so keep that in mind.

sawood12 · Aug 4, 2007

How are you going to maintain brake balance as fitting calipers with larger pistons to the rear will give you more rear bias.

smallspeed · Aug 5, 2007

this was part of the question really.. if the RS/C4 had 4 pot rear and the same fronts as the C2, then I was assuming there was no issue, but it appears the fronts were different too (hence the balance issue is probably overcome automatically by retaining the nearly ratio's).

Having said that the later C2's getting the 4 pot rears points to there being no brake balance issue that can't be overcome with doing this upgrade. Sounds to me like a choice of either 4 pot rear with 3.3T front's or 993TT front's. I know in a lot of cars the rears are left as standard and just the fronts upgraded, but Im aware the rear brakes do quite a lot of work on a 911 (more so than a front/mid engined car) and I currently have the most basic/lowest performance 964 rear offering.. End of the day I will need to overhaul my rear calipers over the winter, hence considering replacement/upgrade at this time; makes sense to me to do these things once [

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Sounds like the change to Hydraulic assistance is out, the question on master cylinder size remains though; would a larger than standard (C2) master cylinder be required for a change to 4-pot rear/big blacks/reds front (as a worst case)??

Ben

kevin · Aug 5, 2007

Rear Bias valve was changed on teh C2 to acomodate the bigger calipers, IIRC it went from 60-55?? but anyways it changed.

Kevin

Hacki · Aug 5, 2007

IMO the decision depends on what you want to do with that car. In 1990 I started with the first version, 2 pod rear. For daily use - alright. The first trackday means that you know you have to change something.
So, if you just want to enjoy your C 2 on public roads without risking anything, the standard breaks will do perfectly - as long as they are in good shape. There are many stages of upgrading the brakes, we had a few threads about it. Some guys chose 928 calipers for the front, others have big reds, front brakes vented, etc..
Check www.fvd.de (site navigation for 964 and brakes is easy) to get an idea about upgrade kits.
Maybe - and that´s a cheap option - overhauled standard breaks and more aggressive pads will be the right choice, or maybe you´ll go for the overkill. Everything is possible, as long as you don´t mix the wrong components.

Rgds

Hacki

sawood12 · Aug 5, 2007

ORIGINAL: kevin

Rear Bias valve was changed on teh C2 to acomodate the bigger calipers, IIRC it went from 60-55?? but anyways it changed.

Kevin

This is the mod that most of the 944 guys who upgrade to big blacks carryout. I've yet to do it and the brake bias does feel very front end loaded. If I didn't have these crummy EBC yellows fitted I think i'd be having real problems.

Guest · Aug 6, 2007

I am in exactly the same situation. This is what I've done so far and am in the process of doing.

1. I bought a full set of 993 callipers (front & rear) from this forum.
2. I replaced the weedy single pot rear calipers with the 993 rears.
3. I am selling the 993 front callipers

So far I have not needed to replace the servo and the standard system works ok as is.
I have noticed the bias does need slight tweaking for the track (the rear squirms a little under HEAVY braking).

However, I aslo intend to replace the front callipers with some 928 big blacks (virtually identical to the big reds but much cheaper). I'm buying these from the USA where the exchange rate is still stupidly good (Lindsay Racing (spelling?))

Once I've fitted the big front callipers and found some bigger discs which will fit the hubs - I can then see if I need a beefier servo to cope.

My advice would be go ahead and fit the slightly bigger rear callipers as it's ok with the current set up.
I'd leave the servo etc alone until you've made a call on what you want to do with the fronts. If you track the car then I would recommend going for bigger front callipers. The standard callipers with a harder pad are ok at some tracks but my local track is Bedford which is a real brake killer so I need a bit more beef.

Nothing worse than crappy brakes on a trackday - so frustrating.

smallspeed · Aug 6, 2007

Currently my car is a daily driver, but over the winter and next summer it will become a weekend/trackday toy. While Ive only done one track day in the car, the standard brakes (which are excelent on the road) are a bit limited on track. My thoughts were to upgrade the rears at this stage (as the one caliper needs looking at anyway) and then look at modifying the fronts as and when (prob spring time).

One option for me might be turbo front disks and calipers, however Im thinking big blacks on the front with C4 rear calipers might be a better way to go.. Seems like it might be easier if the standard master cylinder is big enough for the job too which is a bonus

thanks for the responses so far..

ben