please help identify Calipers - paging Dr Bill V

[andy s]

So while I'm rummaging around, looking for exhaust header gaskets, I open a box and find a set of calipers. 2 are brand new and 2 are used.

The new ones have smaller pistons and are part number 993.352.425.10 and 993.352.426.10

The second set, I cannot find any part numbers on the calipers, but they seem to have larger pistons (about 48mm and 38mm) by my rough estimate.

The new set has 3 1/2" drop hole spacing and the older ones (I am assuming fronts) have vertical holes, so I am assuming I would need an adaptor

I have posted before that I am looking for upgraded calipers for my 75 911, that if my memory serves, has 3 1/2" spacing in the front and 3" in the rear, so I am assuming I need to reduce the hole pattern for the new ones to go on the rear 3" and the calipers are 3 1/2" (smaller pistons) and I am assuming someone sells an adaptor for the front ones?

So here is my question;

Fronts.

1. Who sells adaptors go go from the vertical holes to a 3 1/2" pattern
2. what size and offset rotors work here
3. what pad sizes?
4. who rebuilds and powder coats calipers? - estimate on cost?

Rears.

1. How to I get down to 3" spacing (from the 3 1/2" now)
2. Rotor size and offset?
3. Pad sizes?

Thanks!

[sc]

The 993.352.425.10 and 993.352.426.10 are 993 turbo rear calipers that use a 322x28 rotor...these should have 28/28mm pistons. So a 309x28 930 rear rotor will work on early 911's.

Hard to tell from the pictures if the used set are "Big Reds" or "Big Blacks/S4.... but Big Reds have 44/36 pistons.
If Big reds....they use a 2 piece 322x32 rotor...If Big Blacks, these use a 304x32. For narrow body cars a caliper adapter and a 32mm front rotor or a pre-1980 930 rotor without the 930 hat. You will have to use a custom hat for those floating rotors. If using 930 wide hubs (1981 930 and on) these late 930 rotors will work and are 304x32.

Pads will be whatever you decide fitting a 993.

Rear calipers will need to be re-drilled or the Ears cutoff and re-drilled radial style with adapters
Fronts only need the proper caliper adapter

Check here for info on re-drilling the rears:
https://forums.pelicanparts.com/porsche-911-technical-forum/993492-74-widebody-hot-rod-build.html

Check here for caliper adapters and caliper modification:
Vehicle Craft Inc."VCI" Hi-Performance Brake Upgrades For Porsche Cars

[Bill Verburg]

Originally Posted by andy s

So while I'm rummaging around, looking for exhaust header gaskets, I open a box and find a set of calipers. 2 are brand new and 2 are used.

The new ones have smaller pistons and are part number 993.352.425.10 and 993.352.426.10

The second set, I cannot find any part numbers on the calipers, but they seem to have larger pistons (about 48mm and 38mm) by my rough estimate.

The new set has 3 1/2" drop hole spacing and the older ones (I am assuming fronts) have vertical holes, so I am assuming I would need an adaptor

I have posted before that I am looking for upgraded calipers for my 75 911, that if my memory serves, has 3 1/2" spacing in the front and 3" in the rear, so I am assuming I need to reduce the hole pattern for the new ones to go on the rear 3" and the calipers are 3 1/2" (smaller pistons) and I am assuming someone sells an adaptor for the front ones?

So here is my question;

Fronts.

1. Who sells adaptors go go from the vertical holes to a 3 1/2" pattern
2. what size and offset rotors work here
3. what pad sizes?
4. who rebuilds and powder coats calipers? - estimate on cost?

Rears.

1. How to I get down to 3" spacing (from the 3 1/2" now)
2. Rotor size and offset?
3. Pad sizes?

Thanks!.....

Those are a set of 993tt calipers

first the bias is not really what you want on a 911, it's not unsafe or anything just an inefficient use of resources. i use the same basic calipers on both of my cars but have the 993RS rear versions of those calipers. The difference is that tt has 28/28 rear pistons the RS has 3/36, when using the correct 322mm rotors front and rear bias goes from 1.997 on the tt to 1.426 on the RS, the RS is much closer to where you want it.

Front is no issue at all you can buy the VCI kit or just buy 993tt fronts rotors.


These are 322x32 993RS/tt front rotors on a 993. To use them on a 911 unbolt the hats and bolt os some flat hats






same rotor and caliper as above but on a 911, note the flat hats


VCI has the correct caliper adaptors.

The back is where it gets tricky, the fill and drill method works to use the standard 993 calipers w/ 930 309x28 rotors, I don't know if it will work w/ the tt/RS calipers and 322mm rotors, it may. I use the 993RS/tt 322x28 rotors on both of mine.

there are several hurdles to do this
1) calipers
in all 3 of these pics from L to R stock rear, modified rear, stock front




The rear is a transverse mount w/ ears, the ears need to be machined off and radial mount holes tapped to use the same sort of caliper adaptor as on the front. This is a non trivial job.

2) rotors
To use the 322x28 rotor and retain the parking brake a 911 center section must be adapted to the 993 annulus, first machine a stock center out then attache the 9111 center section, again no trivial

stock 993tt/RS rear on a 993


modified rotor


installed on a 911


VCI uses a 930 309x28 rotor which needs no modification but does the calipers the same way mine are done.

For street use these brakes are way more than any sane person needs stock 993 brakes on 930 rotors is more than sufficient. For track use these are the nuts!!

Finished


PS if you go the fill & drill method, the holes need to be positioned w/ 3" centers and such that the pad is 100% on the rotor, preferably w/ at least 1mm to spare

[Geneman]

bill you are amazing.