Porsche 911 Brake Upgrade Question

[93RSA]

Hey Pelicaners,
So I have been thinking for some time of upgrading the braking on my '74 Carrera, as it is the weak point on the car now, with the stock "S" calipers installed under the correct 15x7 Fuchs in the front. I want to keep the original size wheels on the car, and was wondering what some or any of you had done. Am looking to just do the front calipers at this point, but was wondering what would fit best under the 15's, if anything, and what experience you guys had with 930, 944/951, 911SC, calipers, etc. Any help is appreciated. Thanks!

[djpateman]

With the 15" rims I think only the 930 & 911SC will fit. But the 911SC will not give much if any improvement over what you have.

[DonNewton]

I have Boxster calipers on my 914 track car with both 7X and 8X15 wheels (depending upon weather conditions). Work like a champ. Just need a bracket to install. I just don't remember where that bracket was sourced.

[Bill Verburg]

Originally Posted by 93RSA

Hey Pelicaners,
So I have been thinking for some time of upgrading the braking on my '74 Carrera, as it is the weak point on the car now, with the stock "S" calipers installed under the correct 15x7 Fuchs in the front. I want to keep the original size wheels on the car, and was wondering what some or any of you had done. Am looking to just do the front calipers at this point, but was wondering what would fit best under the 15's, if anything, and what experience you guys had with 930, 944/951, 911SC, calipers, etc. Any help is appreciated. Thanks!

Just changing calipers is NOT an upgrade and you need to do both ens at the same time.

The need for a true upgrade comes from 2 camps
1) track use where the fluid boils - here the solution is first lighten the car, second provide all the cooling air flow that you can to the rotors and calipers third use high temp pads and DoT 5.1 fluid

2) the need for greater brake torque - w/ 15" wheels here you go to 930 930 calipers and rotors or the new 917s from Zuffinhaus

I don't care how may chime in w/ "I'm using...... " fact is they would have been fine w/ #1 or #2

Just remember that the limiting factor wrt to stopping distances is the tires not the brakes and the limiting factor wrt to temp is the abilty to absorb and transport away heat while limiting temp rise

[93RSA]

Bill,
I appreciate the feedback, but I am not looking so much for stopping distance, as the car is not a track car. Just looking for more positive brake feel, as the "S" calipers tend to flex a little under pressure.

[Bill Verburg]

Originally Posted by 93RSA

Bill,
I appreciate the feedback, but I am not looking so much for stopping distance, as the car is not a track car. Just looking for more positive brake feel, as the "S" calipers tend to flex a little under pressure.

'A' calipers are stiffer than 'S', you can also put 'wide A's' from an '84-89 Carrera w/ their correspoding rotors. leave the back alone.

[93RSA]

Thanks! Forgive me for the question as I am not too familiar with the letter designations, but the "A" calipers are from SC's, with the wide "A" calipers being from Carrera 3.2's?

[175K911]

Bill is correct. For street use the Carrera "wide-A" is a nice change, and all you'd need.

The difference between the SC and Carrera calipers is that the Carrera is widened by 4mm to work with the wider 24mm rotor the Carrera changed to. The SC was a 20mm. Same pad, same brake pedal effort and feel, just more mass in the rotor for heat dissipation. So you could bolt the A caliper from an SC on your car, flush the system with good fresh brake fluid and call it quits. Or you could get the wide-A and the Carrera 24mm rotors and go that way.

If you decide to go the wide-A route, let me know. I might be convinced to part with the calipers from my '86. You'd need to source rotors, and I'd recommend our host here.

[Jim Smolka]

FWIW,

84-89 Carrera M callipers on the back have a larger piston area (more rear brake bias) than earlier M calipers. Also, Carreras had a proportioning valve

[911st]

I believe adding Carrera 3.2 front rotors and calipers w stock rears is an upgrade.

You can signifficanly extend you performance with proper sport or race pads and fluid. In fact you can probably get a lot more out of your current set up by just doing this.

You could paint the front calipers and it would look stock.

Modified to fit C2 or 993 front calipers w 3.2 rotors front with Carrera rear caliper & rotors being a step up from this.

Do not try Carrera front and rear calipers together without a rear balance valve.

Both these setups are more about balance and seem to have a very good front to rear balance.

Going beyond these setups will cost a bunch and add to the rotating weight.

[blubayou 911]

What you might forget is that 74's don't come with the later style larger brake booster. For some of the larger brakes, you will need to upgrade to the later style brake booster for a better brake feel.

[Bill Verburg]

Originally Posted by 911st

.........

Modified to fit C2 or 993 front calipers w 3.2 rotors front with Carrera rear caliper & rotors being a step up from this.

......

Please explain to the world just exactly in what way is 964/944 or 993 calipers on 3.2 Carrera rotors an upgrade over 3.2 Carrera wide A caliper on 3.2 Carrera rotors

[Bill Verburg]

Originally Posted by blubayou 911

What you might forget is that 74's don't come with the later style larger brake booster. For some of the larger brakes, you will need to upgrade to the later style brake booster for a better brake feel.

power brake vacuum boosters weren't used on any 911 untill '77

all 911 from '69 thru '76 used the same size m/c, 19.05mm. All normal boosted systems from '77 thru '94 used the same size m/c , 20.6mm.

if you use the large 930/964/993 calipers then yes, you will also need the large 930 size m/c ,23.8mm but you do not necessarily need to use a booster on it.

[KTL]

Are you sure the "flex" you're feeling is not a suspect/failing brake master cylinder? A mushy pedal can be contributed to a number of things:

-Master cylinder seals failing, allowing a pressure loss
-New pads not bedded-in. Bed-in new pads and the firm feel you get is a noticeable difference.
-Rebuilt calipers or retracted caliper pistons can cause an air gap between the pads and the pistons. This produces what some consider a soft brake feel when it's actually added brake pedal travel. Like driving a 1990s-early 2000s Chevy truck with the worst feeling brakes (low, soft pedal) i've ever experienced!

[pkracer21j]

on my s calipers, when bleeding them, you can physically see the caliper "flex" as the brake pedal is being pumped. kinda scary. I have 996 brakes on the shelf for my winter project.

[Kroggers]

These are another nice option, and will fit under a 15" rim...

[RWebb]

I'd pay close attention to Kevin's comment & also repl. 10 year or older rubber brake lines with new. I've never been convinced by the idea that Al caliper flex shows up as a loss of "feel" -- mine always felt great ('75S).


Bill - can you comment on those C-12 setups?

[Bill Verburg]

Originally Posted by RWebb

...
Bill - can you comment on those C-12 setups?

For the thousandth time, Calipers are a decision that comes down the list from the most important choice, ROTORS

when used w/ 3.2 Carrera rotors it makes very little difference whether you use 3.2 Carrera calipers, Boxster calipers, 944/964 calipers or C12 calipers.

There will be minor differences in pad availability and life but that's it.

It is very easy to kludge up a mismatched system, but usually harder to do it right

[911st]

Originally Posted by blubayou 911

What you might forget is that 74's don't come with the later style larger brake booster. For some of the larger brakes, you will need to upgrade to the later style brake booster for a better brake feel.

No booster is probably needed. Some of the 911Spec full race guys are taking there booster off for better threshold braking feel. I believe they are however, running the smallest master cylinder they can get away with.

I am far from a brake expert.

Again, fluid & the right pads are usually all that is needed.

If going up from the alloy caliper just pick up a set of new/rebuilt Carrera calipers and Carrera front rotors to go with the best pads and fluid you can live with.

Again, the Carrera ft/SC rear and C2 front and Carrera rear as noted is more about about a balanced system than adding a large amount of braking reserve.

Forgot, get a lot of air in there if you can.

For big brakes or full race/non Drivers Edd set up, talk to the real experts.

[Kroggers]

Originally Posted by RWebb

Bill - can you comment on those C-12 setups?

What do you want to know?