Affordable Front Brake Caliper Options for '75 911S

[RobertDurff]

Hi Everyone,

I'm in the middle of a complete rebuild of my stock 1975 911S. I sent all 4 brake calipers off to PMB Performance for a rebuild. Unfortunately, it looks like the front calipers (the early S type aluminum ones) have too much pitting in the bores for a rebuild (pics attached if you're interested / have an alternate opinion).

I'm curious about folks' thoughts on what an economical alternative is. Once rebuilt, the car is going to be driven regularly on road trips and around town, but never on the track. Think of it as "touring" use. The front end of the car is stock, so original caliper mounting hardware, Koni struts, etc. I'm planning to run 16" wheels. I haven't had time to research this deeply, but am considering...

- Source used calipers from a slightly later car with the steel calipers (I think these were on the SCs, yes?) and have PMB rebuild those.

- Source used 930 calipers (are those bolt-on replacements, or will I need to modify other things?) and have PMB rebuild those.

- New brake kit from Wilwood or similar. (I don't love the modern look, and it adds yet another $1K to the build).

Appreciate everyone's input!
-Robert

[dg567]

Use 84-89 Carrera calipers - dimensionally the same as SC but allow the use of a thicker rotor.

[911mhutch]

Agree with dg567. Lot's of info here regarding that question and responses consistent with dg567's suggestion. A decent "low cost" 3.5 spacing upgrade that I have done with a number of pre 84 cars for the street that even sometimes hit the track all w/o issue. 84-89 Carrera calipers, pads and rotors.... option of manufacturer for all components is broad from which to select.

[RobertDurff]

Originally Posted by dg567

Use 84-89 Carrera calipers - dimensionally the same as SC but allow the use of a thicker rotor.

Great, thanks! That seems reasonable, and probably easy to source.

[Otter74]

If you look at the 911 parts classifieds, someone is selling a complete set of rebuilt SC calipers for cheap.

[dg567]

I went through this on one of my early cars - went through 3 sets of aluminum S calipers that all leaked after a while. I saw screw it and went with SC stuff which was a great upgrade.

You can't go wrong with either SC or Carrera calipers.

[3rd_gear_Ted]

There is always that oddball guy.

I use the 951 turbo front calipers that look way better painted up than the Carrera calipers.
Brake bias is close enough for street use, you have to mod the mounting ears and they use the Carrera rotor also.
Raced on the track many years with 275 x 295 tires, knowing eventually I wanted a cars & coffee G-body car that can look pretty.
Front brake calipers are like boobs in some circles.

[dg567]

Originally Posted by 3rd_gear_Ted

There is always that oddball guy.

I use the 951 turbo front calipers that look way better painted up than the Carrera calipers.
Brake bias is close enough for street use, you have to mod the mounting ears and they use the Carrera rotor also.
Raced on the track many years with 275 x 295 tires, knowing eventually I wanted a cars & coffee G-body car that can look pretty.
Front brake calipers are like boobs in some circles.

Those calipers require using the 951 Fuchs with higher offset and more inner clearance, correct?

[3rd_gear_Ted]

Originally Posted by dg567

Those calipers require using the 951 Fuchs with higher offset and more inner clearance, correct?

I do have modern 18" wheels with lots of tire options and I like the fill that size tire creates in the turbo flare wheel wells.
16's are just ....

[Bill Verburg]

Originally Posted by 3rd_gear_Ted

There is always that oddball guy.

I use the 951 turbo front calipers that look way better painted up than the Carrera calipers.
Brake bias is close enough for street use, you have to mod the mounting ears and they use the Carrera rotor also.
Raced on the track many years with 275 x 295 tires, knowing eventually I wanted a cars & coffee G-body car that can look pretty.
Front brake calipers are like boobs in some circles.

The problem w/ using 964 fronts or 951t fronts or Boxster S fronts besides ruining bias is that they are all designed for a 28mm thick rotor, the minimum thickness for them all is 24mm

unless the O/P has done significant motor work, it's very unlikely that he will need more than the stock 20x286 front rotor and SC A calipers. Though If the wide As are available w/ the 3.2 24x286 rotors they do no harm and do provide a bit more thermal headroom.

and yes the 944 7s are wanted w/ the 964s unless a 5mm spacer is used w/ 911 7s

[nickelplated5s]

Originally Posted by 3rd_gear_Ted

There is always that oddball guy.
Front brake calipers are like boobs in some circles.

I won't go there but you left too much... Go over to Early911Sregistry.com and search my user name for Alfa Brembo.

BillV is correct. My Boxster setup, on a 67, has front brake bias even with the 22.5 MC. On one hand it stops. On the other hand I added >200lbs with rotors and such. By all accounts PMB is great. Didn't know about them before my expensive path.

My advice is go big and live with the bias.

[Bill Verburg]

too much front bias isn't dangerous like too much rear. It's just a waste of potential braking resources. After experimenting w/ many combos you want ~1.5+/- .2 w/ a nearly stock setup, when the car is more stiffly sprung, lower and w/ effective LSD ~1.42 is useable most of the time. Anything above ~1.5 is certainly safe but wastes a portion of the potential. Yes, fine for street use., Bu in a track environment it also strains the already over worked fronts

here's a comparison of some systems, you can pick and choose your own combos and do some arithmetic to see the various resulting bias. 964 uses the same calipers and rotors as 944t or 951t

[nickelplated5s]

I brought it up once but there are solutions for the bias issue. First would be a custom MC for the bias. Lots of math and trial and error. Obviously specific to the car and setup. Second would be to plumb in a bias valve after the MC. The fancy pants way would be to plumb the bias valve into the cockpit. That, of course, would bring up ID and line run lengths. I'm sorta serious but also poking fun for the ME's here. Justa thought but love my Boxster setup.

[Bill Verburg]

Originally Posted by nickelplated5s

I brought it up once but there are solutions for the bias issue. First would be a custom MC for the bias. Lots of math and trial and error. Obviously specific to the car and setup. Second would be to plumb in a bias valve after the MC. The fancy pants way would be to plumb the bias valve into the cockpit. That, of course, would bring up ID and line run lengths. I'm sorta serious but also poking fun for the ME's here. Justa thought but love my Boxster setup.

The only way to change bias w/ a m/c is to use a stepped m/c or twin master

there are a few stepped ones available for power brake cars none that I know of for non-boosted

A bias valve should only be used on the rear circuit and when so used only reduces rear bias, in other words it moves bias further forward


at least Boxster calipers are designed for 24mm thick rotors

If you use Boxster front then the best rear match is wide M rears, no ideal but better than Boxster/Boxster

also don't confuse Boxster w/ Boxster S which want 28mm rotors

[Cairo94507]

I swapped in the '84-'89 front calipers and 24mm rotors on my '71 914-6 after the early S aluminum calipers just did not perform the way I wanted. I have a 19mm master cylinder and GT rear 914-6 calipers. The braking is exceptional; I could not be happier. I should mention this is a street driven car with a 3.6 in it. I know the front calipers and rotors add a little bit of unsprung weight, but it is street driven- not a concern for me.