1990 964 front calipers on a 1977?

[dfhtrhjn]

The front calipers on my 1977 might be due for a rebuild here soon, and there's a guy in my area with a wrecked 964 he's parting out. The front calipers are still available.

Is it possible/worth it to swap my 1977's S calipers to the 964 ones rather than rebuild the originals?

[Bill Verburg]

Originally Posted by dfhtrhjn

The front calipers on my 1977 might be due for a rebuild here soon, and there's a guy in my area with a wrecked 964 he's parting out. The front calipers are still available.

Is it possible/worth it to swap my 1977's S calipers to the 964 ones rather than rebuild the originals?

It's possible but If I were you I'd rebuild your stock calipers, when you start down that path you are opening a can of worms which leads to over $3k worth of work for free calipers

[Bill Verburg]

Originally Posted by dfhtrhjn

That was my worry too. The reason I ask though is that looking at pictures, the 964 caliper doesn't look a lot bigger than the S caliper for my '77. I could just machine a little rectangular adapter to mount it.

The problem is I don't know if there's anything else needed to get it mounted correctly since I've never tried it. If the adapter and 4 bolts are the only equipment, then this would be really easy to do, easier than rebuilding the old ones.

I really hate to go over this for the 100th time, but here goes
yes, the 964 calipers can have their mounts hogged out to fit a 911 3.5" strut, but what do you gain? Yes, a bit more thermal mass(did you need that?) because you use the thicker 3.2 Carrera rotors(but you could use these same rotors w/ 3.2 Carrera front calipers for the same result). Yes, you get more brake torque in front(IS that what you want?) but the price paid(besides monetary) is a dangerously heavy front bias(unless you do the back too), Additionally the brake pedal will be mushier unless a bigger m/c is used and the only one the fits easily is just a tad too big(unless you do the backs too). Lastly the 964 front calipers want a 28mm rotor w/ 26mm as the design min, do you really want to use them on rotors that start at 24mm and go down from there?

to do it right, the 964 calipers need to be converted from radial to axial mounts and used w/ 930 32x304mm rotors, in back you plug the stock radial mount holes and redrill to be used on 930 309x28mm rotors, and then you use a 930 mc which is still a tad big for these calipers but close enough, this is all quite expensive even if you can find a machinist that knows how to do it.

[dfhtrhjn]

Easy there buddy, no reason to get frustrated.

Thanks for the info, there was a lot in there I wasn't able to find searching online or looking through caliper adapters.

[Flat Six]

Originally Posted by dfhtrhjn

Easy there buddy, no reason to get frustrated.

Thanks for the info, there was a lot in there I wasn't able to find searching online or looking through caliper adapters.

Brake sizing and dynamics are complicated (at least to me), and making one change alters the balance and effectiveness of the entire system. IMHO Bill Verburg is one of the most knowledgeable guys out there re: braking systems. He's anticipating -- and proactively answering -- the follow-up questions that your initial inquiry would require, plus giving you at least a top-line rationale for why your initial idea will either be less effective than your stock setup, a money pit, or both.

Click the third link in his signature line ('Rennlist Brakes') and you'll find a wealth of information on various caliper / rotor / master cylinder / booster / pv combinations and how those combinations affect braking effectiveness and -- as he pointed out in his post -- F/R bias.

Where brake systems and wheel fitment are concerned, I give Bill and his knowledge a metric cr@pload of respect.

[Rodsrsr]

Bill is the "Yoda" of brakes.

[DanS911]

the only thing I don't agree with in this thread is that it is probably more than 100 times for Bill

Been there done that and ended up adding a Tilton brake bias that i had to crank 100freakin % to not ruin all the front tires in the world.
My questinn is why have we not found a cost effictive rear caliper/rotor set up to go with the various front options

[pavulon]

Don't own a P-car (maybe someday) but stop to read Bill's posts each time I see one. The guy is a great asset to the board and I'm sure everyone appreciates his detailed contributions. Thank you Mr Verburg!!

[unclebilly]

Here is what I recommend based on racing experience.

1. Buy some good pads - I run Pagid Yellow RS29s front and rear on my 77 Track car - these work fine on the street.
2. Rebuild your stock calipers (all 4).
3. Machine or replace your rotors.
4. Put in Brembo LCF600+ brake fluid. be sure to get all of the old stuff out. Do not run ATE brake fluid such as 'Super Blue' this is junk and will boil with a stock system under extreme use.
5. Take it out on the highway late at night and bed in the pads.

You will never look back and you will have enough brake there for street, DE, PCA Club Racing, emergency stops because there is a rattle snake under the seat, bees, whatever.