No booster 930 brakes

[creempuf]

Have a question for you all.
930 calipers with no brake booster. Will this work?
Will the pedal be too heavy?
Would I minimally have to install a larger diameter master cylinder?
Will it be just fine?
Just don’t ask me why I’m doing this!
Maybe I want to upgrade a 76 930 to 930 calipers, yes I know the rear control arms are different. I’m aware of other things I would have to change just wanna know if the car will be drivable or is this a stupid idea? Aluminum S calipers suck!

[356911930]

1. yes
2. depends on what you like. Most think it's fine
3. it would be best
4. original master cylinder will feel mushy due to increased volume of fluid needed to be pushed
5. Ok I won't ask
6. rear 930 calipers can be machined to accept the 1976 3"rear bolt spacing. I have a set of willwood or bremtec 3" bolt spacing that are designed to match up with 930 or larger front calipers that I might sell? Not sure if I want to get rid of them.
7. Aluminum S calipers are good up to up to about 90mph with this weight of car. In a 2,200 -2,300lb car they are fantastic. Most of the difference is in heat capacity during extended breaking periods as on track.

Rahl

[creempuf]

Great reply, just what I needed to hear. this helps tremendously. Thanks Rahl

[infraredcalvin]

I did this on mine, not that hard, but you need special rotors. For the rears, I didn’t want to ruin my newly purchased 930 calipers by machining them to fit on the existing carrier, the 76 should have dog ears casted in place (future mounts for the 917 brakes on race cars?), but not drilled and tapped, I “machined flat” the ears, drilled and tapped on a large drill press. Everything bolted together nicely. You have to use a Mercedes 23 mm MC. Too much volume for the stock 19mm MC. I did a lot of research on it way back when, got help parts and great advice from Steve at Rennsport Systems and compared with some of the kits from VCI. Both costs were within a couple hundred, I went with Steve (was more expensive) cause he spent at least 2-3 hours talking me though options, theory’s, etc, and then even called to follow up after I bought and installed parts!

Happy to answer any questions you may have...I love the 930 brakes, I used to overheat the s calipers with spirited drives, haven’t come close on the 930 brakes...

[bpu699]

When my 930 had a mechanical issue on the track I had to get towed. I can tell you that with the motor off, and race pads, I had near zero braking ability. Felt like I was going to ram the tow truck each time he slowed down...

Yet with the motor running, booster working, slowing from 100mph plus was no issue...

[911tracker85]

I went with Steve (was more expensive) cause he spent at least 2-3 hours talking me though options, theory’s, etc, and then even called to follow up after I bought and installed parts!

RS is doing my 930 rear calipers, engine case rebuild, recon rods/rockers, rebuild heads, and probably other stuff I have forgotten what I sent.

I have been working on the restoration of my 78 SC/930 with Steve, and he had helped me on my other 911 in the past.

I was talking to another 930 owner in the past and he said he talks to Steve often for advice but does not buy from him because of shipping cost and he is not the cheapest for the parts.

cheapest? I believe you get what you pay for and am willing to pay the shipping and cost for Steve's shop to do my work, as well as buying lots of other parts.

I believe his knowledge of these cars is invaluable..... hard to place a value on that.
Steve is such a great guy, he knows people call him for advice and do not buy stuff. but he still helps.

I should start getting stuff back from him shortly. in the final phase of blasting my tub to metal for paint.

[creempuf]

Well it didn’t take much looking around to find what I believe would be the most hassle free upgrade to the aforementioned 23mm master cylinder. Looks as though Uro parts make what they call a 23mm Big Bore MC for porsche specific applications. From looking at the photos, all the ports are in the exact same location as the original 19mm MC so this should be a piece of bundt cake.

[spuggy]

ATE made the master cylinders (and brake boosters) for Porsche. For non-boosted 23.8mm (actually 15/16", because brake parts are still imperial sizes) applications, there is a master cylinder from a MB that is usually used. Don't know how many of your original components are swappable/usable - but for non-boosted cars Bill V usually advises to use the specific kit that comes with the correct actuating rod, fittings etc.

I have no idea of the quality of the Uro parts. ATE has been OEM for brake components since these cars were new, the original in mine lasted 100's of 1000's of miles, and cost about $200 new. Seemed like a no-brainer to me.

[Rawknees'Turbo]

Originally Posted by creempuf

Well it didn’t take much looking around to find what I believe would be the most hassle free upgrade to the aforementioned 23mm master cylinder. Looks as though Uro parts make what they call a 23mm Big Bore MC for porsche specific applications. From looking at the photos, all the ports are in the exact same location as the original 19mm MC so this should be a piece of bundt cake.

If you do a search in 911 Tech for "Uro brake master cylinder", you will not like what you find.

[panzerfaust]

homologated special 3.0 SC/RS had no booster with 3.3 calipers. its used twin MC if memory serves.

i can see no reason why no boosters wouldnt work. some folks dont like the heavy stiff unboosted feel on the streets. depending on the year 76/77 they when with a longer pedal arm for mechanical leverage. this would help if your car is heavy or to help reduce the efforts. curb weight was listed at 2330lbs for the 954. in 84, according to porsche, it was the fastest accelerating factory street car... 930 included.

[infraredcalvin]

Originally Posted by Rawknees'Turbo

If you do a search in 911 Tech for "Uro brake master cylinder", you will not like what you find.

Go with ATE, I ageee with tThe sentiment above...

BTW - the location of the top supply hoses is tight with the aluminum crossbar, so it’s a real PITA to get the flared feed hoses seated, but it can be done.

Also on my first pass I machined a bullet looking adaptor to fit inside the MC as you need a longer rod from your brake pedal. I eventually bought a replacement ATE MC from rebel racing that included a longer rod...

[panzerfaust]

Pelican or other places sell the Ate 23mm for unboosted 3.3 brakes. The ports are located different and comes with the longer rod if memory serves

[speednme1]

My 77 930 has boosted brakes and they feel pretty decent during normal driving but I certainly understand why later 930 brakes would be a better upgrade. From what I was told some late production 77 930’s received the later 930 brakes in the front only. Unfortunately mine has the S calipers. For those upgrading to later 930 calipers will you be using the floating rotors as well? Or will you update to later 930 front hubs and just go with non floating 930 front rotors?

[infraredcalvin]

Keep your hubs, when you purchase the rotors from one of the above mentioned sources they offer a locking or floating rotor option. I’m happy with the locked rotor... plenty of brake for out lighter 3.0s.

[911tracker85]

from this thread I am hoping someone can answer my question.

I have a 78 SC/930 conversion. PO who built it left the SC brakes and suspension.

I got a set of 78+ 930 calipers. sent the rear to Steve Weiner for modification to fit the SC banana arms. I have cut off the little ears to allow them to fit the arm. as far as I know the front hubs are SC but got a set of RS reinforces raised spindle Belstien struts.

Steve had told me I should use 993 turbo F/R rotors with my setup. unfortunately he was not more specific. unfortunately Steve is not available for a while.

talked to one supplier and he is not familiar with this and not comfortable recommending.

does this make sense? and if so which rotors?

[911tracker85]

PS not interested in floating rotors....

[infraredcalvin]

I’ll check tonight and see if I can find my old invoice, but I believe the 993 turbo rotors sound familiar. But I do recall Steve telling me he milled a few mm from the edge as the diameter is a little too big for the turbo brakes.

In the meantime look up “VCI brakes” and click on the “930 turbo caliper upgrade” link, it gives some info, I’m sure they’ll sell you their rotor setup too.

[911tracker85]

thanks. took a quick look. hope you find the invoice with the info on the rotors.

[infraredcalvin]

Hmmm, I looked in multiple places, can’t seem to find my receipt.... sorry about that...

[911tracker85]

so ANYONE know what rotors work on my setup? test fitting the rears.