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Thread: help with brake upgrade

  1. #1

    help with brake upgrade

    I am soon to mate a high power motor (280hp approx) with a lightened 72 body and want to explore brake update options so plese tell me what you have done, cost and performance.

    Useage will be mainly street but an occassional track visit.

    930 turbo, boxter updates aftermarket 4 spots etc etc tell me what fits easily, what adapters I may need, discs, pads etc just assume I am a dummy as I am!!!!

    Currently has STD cast iron calipers front and rear and STD discs
    Last edited by BOYER73S; 03-07-2011 at 08:23 PM.
    Clyde Boyer





    1973 2.4E Coupe RHD Aussie 5 speed
    1973 2.4E Coupe RHD Aussie 5 speed my first ever 911 (1995)







    Early S Registry Member #294
    First Aussie R Gruppe Member #366
    TYP 901 Register Inc #6

  2. #2
    Turbos are the easiest, but not the cheapest. They will fit 15 inch Fuchs and were good enough for the 917. Rotors are heavier, calipers (Aluminum) are light but not as light as the S calipers. The rears should be lighter than the steel M I think.
    1971 911S, 2.7RS spec MFI engine, suspension mods, lightened
    Early 911S Registry Member #425

  3. #3
    We have fitted several 3.3 turbo conversions - normally with a bias bar pedal box.

    If you stick with the 19mm tandem cylinder the brake balance front to rear will be virtually idential to the standard braking set up.

    Pedal effort will reduce by around 20% for a give clamping force but travel will increase.

    If you fit a 23mm tandem master cylinder then pedal force will increase slightly for a given clamping force and travel will reduce. I think that this may have a slightly wooden feel depending on pads - the choice of whch would be very important.

    If you want to have adjustable bias I would use 5/8" diameter cylinders front and rear. This would give standard brake balance (62/38) with the adjuster in the middle of its travel and would give a very slight increase in pedal force for the same clamping force assuming a standard pedal ratio.

    It would be helpful to also increase the pedal ratio to about 6.0:1 with this set up as then the pedal effort falls a little.

    With this set up and decent pads (Ferodo DS3000 are not bad value) the feel of the brakes is excellent, stopping is very good and travel is just enough to allow cadence braking on poor surfaces.

    There is a school of thought that fits different sized master cylinders front and rear on bias bar pedal boxes.

    If you use the 3.3 Turbo brakes with 0.7" front and 0.625" rear then brake balance at the mid point of the adjuster becomes about 55/45. Pedal effort would increase about 15% for the same clamping force.

    I have always thought that the balance on a 911 was not bad as standard and therfore start to adjust from this point rather than move to nearly 50/50 and use some of the adjustment range just to get back to standard.

  4. #4
    Senior Member
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    The three options as I see them:

    -Carrera 3.2

    -Boxster

    -930 Turbo (3.3 '78-89)

    Carrera 3.2 are about the same price as 911SC, yet the discs have more mass, thus more heat capacity. The most important thing in a brake upgrade is increased heat capacity (bigger rotor). However, this adds rotational unsprung mass (which is the worst 'type' of mass to add to the car). This brake package also changes to an iron caliper. You'll need the proportioning valve, Carrera 3.2 rotors, and Carrera 3.2 calipers. Compared to aluminum S brakes, the iron caliper will feel much better. This is the easiest and cheapest way to go.

    The Boxster calipers generate more friction than the Carrera3.2 calipers, which makes them feel better than the Carrera3.2. However, the Boxster calipers simultaneously put more heat in the Carrera rotors so it is a more stressed system and I would recommend this if you want really good brakes on the street but you are not continually beating on them as you would at a trackday.

    The best, heaviest and most expensive: 930 Turbo brakes. These do not require a proportioning valve, because the native bias is very good. The rotors have significantly more heat capacity than the Carrera 3.2 (also significantly more mass). The calipers are legendary and fit underneath 15" wheels. You will need to machine the rear to accept 3" bolt spacing, on the 930 it is 3.5". On the front, you will need a special rotor, for which I recommend the 993TT special machined rotors that Steve Weiner of Rennsport Systems sells for the 911 application of the 930 brakes. The aftermarket 930 rotors (Coleman) are crap, I hear. You will probably want the 'floating' front rotors w/ the adapter hats that Steve W sells. You MAY want to change your master cylinder. Stock 911 is a 19mm, which will give you a long-travel pedal. Race brakes are usually small-travel, force-modulated pedals, not long-travel, distance-modulated pedals. The 930 used a 23.8mm master, however it was boosted. Most users get the Mercedes Ate 23.8mm master cylinder for non-boosted brakes. I have read enough to wish there was an intermediate size, between 19mm and 23.8mm, to maintain good pedal feel for a non-boosted car; the solution seems to be a 1989-94 VW Corrado Non-ABS master cylinder in a 22.2mm size. I have not tried that yet so it requires more investigation.

    For your use I would probably say the Carreras are the way to go. I am not a big fan of the Boxster upgrade, and it sounds like the added mass of the 930's is not necessary given that the car is mostly a street car.
    Last edited by YTNUKLR; 03-08-2011 at 10:40 AM. Reason: clarification ; 1975-77 Turbo brakes = S brakes
    scott kinder
    kindersport@gmail.com

    Registry #614

    9110220587 - 1973 RSR revival in progress
    My Car Thread: "Five-Eighty-Seven..."
    “If it isn't there, it didn't cost anything, it doesn't weigh anything and can't break." - From the philosophy of Grady Clay

  5. #5
    Well, I will take any of those flexy S calipers you dont want.
    1971 911S, 2.7RS spec MFI engine, suspension mods, lightened
    Early 911S Registry Member #425

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