Brake Balance Help Needed | FerrariChat
Buy

Brake Balance Help Needed

Discussion in 'Technical Q&A' started by stephens, Feb 11, 2006.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. stephens

    stephens F1 Rookie
    Lifetime Rossa

    Feb 13, 2004
    4,647
    Australia
    Full Name:
    Stephen S
    #1 stephens, Feb 11, 2006
    My car has had a dual master cylinder/balance bar converson, but we are having a bit of trouble getting the brake balance front to rear right, along with a bit of pedal movement. To help pedal pressures, which were too high, even for this sort of setup, the front master cylinder bore was reduced, but now even with the balance bar on full front, I am having rear brake lockup. I am being told that the change should have moved the brake balance/bias forward, but this just hasn't been the case.
    If you decrease the master cylinder bore of the front brakes on a dual master setup, everyhting else staying constant, will you move the brake bias frontwards or rearwards?
    My theory is the smaller bore requires more pedal movement to displace same amount of fluid. Since the rear does not change, brake balance would move rearwards. The reason I ask is I was told the exact opposite today, which doesn't make sense to me.
     
  2. 308QV_Ohio

    308QV_Ohio Guest

    May 29, 2004
    42
    Columbus, Ohio
    Full Name:
    Steve Kerns
    #2 308QV_Ohio, Feb 11, 2006
    Decreasing the front master cylinder piston diameter will increase the amount of pressure generated in the fluid for the front brakes (with the same pedal force).

    Pressure generated by the master cylinder = brake pedal output rod force / area of master cylinder piston

    By decreasing the area of the master cylinder piston you are increasing its output force. It will also move less fluid... giving you a longer pedal. This will increase the overall clamping force of the front calipers and move the brake bias forward.

    Hope this helps.
     
  3. ferrarifixer

    ferrarifixer F1 Veteran
    BANNED

    Jul 22, 2003
    8,520
    Melbourne
    Full Name:
    Phil Hughes
    #3 ferrarifixer, Feb 11, 2006
    Yes, but on a tandem set up with swing arm, the pressure reaction comes back through the swing arm into the other cylinder. Equalising things.

    Bias is adjusted by moving the centre of pressure/push rod connection point between the two cylinders.

    Pedal travel/pressure should be adjusted by pedal fulcrum/pushrod ratio.

    Calliper volume should influence cylinder choice in the design stage.

    FYI 360 GT come with either 21mm cylinders, front and rear for "gentlemen racers", and professionals are recommended to use 22mm front and rear.

    The 360 GT can use it's ABS if regulations permit, but Bias must be set centrally, and the system incorporates a pressure reducer for the rear.
     
  4. stephens

    stephens F1 Rookie
    Lifetime Rossa

    Feb 13, 2004
    4,647
    Australia
    Full Name:
    Stephen S
    #4 stephens, Feb 12, 2006
    Decreasing master cylinder bore did move brake bias forward. I was at the track today and had no rear lock up problems and had to move the bias rearwards, which is interesting because on the street the backs were locking first.
     

Share This Page