Fitting Brake Servo

[niall]

Hi

I have a 1975 911 which does not have a brake servo.

Is it easy to fit a brake servo from a 3.0SC, if i get a complete servo including the con rod?

Also is the servo from a 3.3 turbo model different/better?

Regards
Niall

[spuggy]

Originally Posted by niall

Also is the servo from a 3.3 turbo model different/better?

The servo from a 3.3 turbo is 8" instead of 7" like the mid-year/SCs/Carreras, and has several different ratios, depending on year.

It's also fitted with a 23.8mm M/C, which is likely too much for small piston calipers - like the mid-years/SC/Carreras. The master cylinders interchange, though.

Don't know about fitting the servo to a non-boosted car - but it's not often done, there's gotta be a reason for that...

[niall]

Thanks Spuggy

I found few threads regarding fitting a servo, I know now why its not often done. You got to do some panel work up front to mount it and recess into floor, also run the air line from the back, not a quick job, and apparently the only gain is less pedal effort required and a sponey pedal according to some members (who like the feedback from the older system).

Ideally I just want to improve the braking performance of my non boosted 1975 2.7.

Will an all round caliper upgrade possibly be an option for me. e.g. Boxster calipers or 3.2 calipers?

A bolt on option is what I'm looking for ideally.

Regards
Niall

[javadog]

Niall,

The brakes you have on your car already are powerful enough to lock up all 4 of your tires, so what exactly are you trying to gain here? A servo just decreases the pedal effort, it doesn't make the car stop any faster. The same thing is true of larger rotors and calipers, in that they won't necessarily stop the car any faster.

JR

[trak ratt]

Don’t think there are any bolt big brake kits for the 3” struts though some of the bigger calipers w/adapters like the Boxster kits might work with new adapters. You would likely want to upgrade the rotors to the Carrera 24mm size then too.
But why not just rebuild your stock calipers, replace brake lines, add some “performance pads” and new fluid? Replacing the struts with the later 3.5” mounts would give you a lot of options but costly unless you can find a good set of used ones, or need to replace at least one of the old ones.

[niall]

Thanks for the advice.

Your probably correct regarding original equipment being adequate.

I was toying with the idea of a brake upgrade, but if the OE is ok for road use and maybe the very odd track day, I should maybe change to braided hoses, better pads and an all round service..

Regards

[spuggy]

Originally Posted by niall

Thanks Spuggy

You're welcome.

Originally Posted by niall

I found few threads regarding fitting a servo, I know now why its not often done. You got to do some panel work up front to mount it and recess into floor, also run the air line from the back, not a quick job, and apparently the only gain is less pedal effort required and a sponey pedal according to some members (who like the feedback from the older system).

Sounds like a lot of work, yeh.

Originally Posted by niall

Ideally I just want to improve the braking performance of my non boosted 1975 2.7.

Will an all round caliper upgrade possibly be an option for me. e.g. Boxster calipers or 3.2 calipers?

A bolt on option is what I'm looking for ideally.

Regards
Niall

Depends what kind of "upgrade" you're looking for, what you feel needs improving.

If it just feels like they're not working well, they'd probably benefit from a good service, flush, clean, lube, new pads etc. If they're borderline at DE's try high-temp brake fluid and/or cooling setups.

If they don't bite enough for your liking, try some high-performance, high coefficient of friction pads like EBC Yellowstuff, or Porterfield.

If you have the front struts with the 3.5" caliper spacing (forget when the changeover was, exactly), then you could bolt on either SC or 3.2 calipers front and/or rears.

There are several types of caliper you might have (I copied this from Pelican's brake pad page):

Steel 'M' Caliper, 911 (1974-early 75)
Aluminum Alloy 'S' Caliper, 911 (1974-77), 911 Turbo (1976-77)
Steel 'A' Caliper, 911 (late 1975-83), From VIN# 911-520-2046 (Coupe), 911-521-1218 (Targa), 911-540-0342 (Carrera Coupe), 911-541-0148 (Carrera Targa)
Steel 'A' Caliper (wide), 911 (1984-89)

I've read that the steel calipers are stiffer than the sportier (lighter) alloy 'S' calipers. Also read that the alloy calipers don't deal with extreme heat as well as the steel. Both hearsay (my 77S had 3.2 brakes when I got it), so use a pinch of salt.

The SC brakes wouldn't be much of an upgrade, as you already have 20mm rotors - in fact, if you have steel 'A' calipers, you already have SC brakes

If you go with 3.2 calipers (and their 24mm rotors), you should fit a proportioning valve, as the larger rear piston will make it very rear-biased.

If you use SC calipers/rotors rear and 3.2 calipers/rotors up front, that should retain the factory bias without a P/V, whilst adding thermal capacity to the fronts (which do most of the work anyway) - should work nicely.

I'm not sure, but I seem to recall reading that the 3.2 calipers (Steel, 'A' wide) are made wider (to fit the 24mm rotors) with a spacer. In which case, if you had the later steel 'A' calipers, you could probably convert them in the process of overhauling.

Boxster calipers are lighter, stiffer, look nice and are 4 piston calipers (better feel/pad life). They're also a lot more money for the conversion, and the limiting factor of the system is still the thermal capacity of the rotors, especially the front. You would probably need to fit the ATE Mercedes truck non-boosted master cylinder for those - Bill V. says to buy the kit, and he should know.

You should do some research on stainless lines before buying them. I wouldn't use them.