Track guys , Brake Bias valve | FerrariChat
Buy

Track guys , Brake Bias valve

Discussion in '308/328' started by Steve King, Jul 4, 2006.

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

  1. Steve King

    Steve King F1 Rookie

    Feb 15, 2001
    4,367
    NY
    #1 Steve King, Jul 4, 2006
    For you track guys , have you replaced the Brake Bias valve with an adjustable one and what is your setting for track and street. After looking at my front brake rotors vs the rears it appears that the rears take most of the braking. I don't see any problems with the fronts and after the rebuild the and checking all of the lines (installed SS hoses last year) it appears the system is functioning correctly. Don't know if the bias valve is working right because I don't believe there is a way to verify it unless you put in a pressure gage in both the front and rear lines. Also if you replaced the valve with an aftermarket adjustable one what make and model did you use. Just asking , Enjoy the ride.
     
  2. miketuason

    miketuason F1 World Champ
    Owner Silver Subscribed

    Feb 24, 2006
    15,808
    Cerritos, CA.
    Full Name:
    Mike
    #2 miketuason, Jul 4, 2006
    Try pegasusautoracing.com
     
  3. enjoythemusic

    enjoythemusic F1 World Champ

    Apr 20, 2002
    10,676
    Worldwide
    Full Name:
    Steven
    #3 enjoythemusic, Jul 4, 2006
    Steve,

    While i do not use a bias adjustment, your comments about the rear doing more than front concern me. Did you put the bias adjust on the front or rear lines?
     
  4. stephens

    stephens F1 Rookie
    Lifetime Rossa

    Feb 13, 2004
    4,647
    Australia
    Full Name:
    Stephen S
    #4 stephens, Jul 4, 2006
    Isn't a bias valve actually just a pressure limiting valve?
     
  5. ProCoach

    ProCoach F1 Veteran
    Owner

    Sep 15, 2004
    5,465
    VIR Raceway
    Full Name:
    Peter Krause
    #5 ProCoach, Jul 4, 2006
    That's correct! The "bias" valve is merely a limiter for brake line pressure to the rear brakes. Ideally, you should be running 100-200 degrees F cooler in the rears than the fronts. You ALWAYS want more front brake than rear. In the wet, most racers dial in a little more rear because they're not concentrating on threshold braking.
     
  6. enjoythemusic

    enjoythemusic F1 World Champ

    Apr 20, 2002
    10,676
    Worldwide
    Full Name:
    Steven
    #6 enjoythemusic, Jul 5, 2006
    Last edited by a moderator: Sep 7, 2017
    Amen! And that is why i am concerned when he says the rear does more then the front. The attached PDF is how the setup here operates. Most Fchatters know Eric Dahl of Girodisc (Fchat sponsor) is the guy who originally designed the brakes for the 308 and has been VERY helpful in 'redesigning' my brakes track use.

    Details: Brembo slotted fronts with Brembo DS1100 pads while the rear are Girodisc slotted rotors and Ferodo DS3000 pads. Goodridge brake lines. Also of note, have removed the 308's stock front fog lights, installed ducts there and routed brake cooling to the rotors.

    STEVE KING: be very careful with that brake bias, please.
    Image Unavailable, Please Login
     
  7. Steve King

    Steve King F1 Rookie

    Feb 15, 2001
    4,367
    NY
    #7 Steve King, Jul 5, 2006
    Steve if I am reading your charts correctly in the OEM chart is looks like 69% front and 31% rear Bias. I have not touched the OEM set up so my Bias valve is stock factory. I was trying to get a feel on what pressures were for the fronts and what for the rears. I am considering getting the Bias valve (pressure limiting valve) rebuilt because I don't believe that the fronts are working as hard as the rears. I don't see this as rocket science but just a matter of getting the numbers and verifing what I've got. So far I havn't seen the pressure numbers anywhere so I was wondering if anyone had them. Buy the way all calipers are working and doing a visual check on the brake fluid didn't show any other problems. All 4 corners bled out OK and total system is flushed. If I pull the rubber cap off of the bottom of the Bias valve it looks rusty so I don't know if this is a normal condition. Mind you this is a weekend street use car so there is no big deal looking at tracking the car. Any numbers would be appreciated. Enjoy the ride
     
  8. Cannoli

    Cannoli Formula Junior

    Nov 7, 2003
    356
    California
    Full Name:
    Norman
    #8 Cannoli, Jul 5, 2006
    Steve, do make sure that the brake pads that are being used are the same manufacturer/model, otherwise you will (or most likely) have a miss-match of coefficient of friction of the brake pads. This will induce a F/R brake bias that is not within the stock specifications.

    When I upgraded my stock 278mm rear brakes on my MB 500E to Euro-300mm, I initially had two different brake pad manufacturers installed between the front and rear. I experienced a rear bias in the brake system. Once I changed all the pads to be the same manufacturer/model, the stock brake bias was achieved.

    One could use F/R pads with different coefficient of friction, but this must be considered when one is balancing the brake system.

    For more reading of this subject as well as Brake Technology in general, check out this StopTech link:

    http://www.stoptech.com/tech_info/tech_white_papers.shtml

    Good luck.
     
  9. enjoythemusic

    enjoythemusic F1 World Champ

    Apr 20, 2002
    10,676
    Worldwide
    Full Name:
    Steven
    #9 enjoythemusic, Jul 5, 2006
    Last edited by a moderator: Sep 7, 2017
    See below PDF. This has bone stock balance, Girodisc fronts with overall balance (better), and Brembo (too far forward balance if you change nothing else).



    That makes sense as the fronts should be working harder. The previous owner redid the brake MCs on the car here about 2 months before he sold the car. Anywho, se the below pdf for all the numbers/calculations. Like Cannoli said, you need to keep to stock pad coefficient for stock feel-/design or uprate front and rear evenly to keep the balance.

    Only crazy guys like me mod it all the last n'th or so and buy $$$ in pads to find the right mix/feel. Hope the below pdf helps.

    A HUGE THANKS to Eric Dahl of GIRODISC as he is the go to guy for all your brake needs. He designed the system so we are very, very blessed to have him on fchat.
    Image Unavailable, Please Login
     
  10. Steve King

    Steve King F1 Rookie

    Feb 15, 2001
    4,367
    NY
    #10 Steve King, Jul 5, 2006
    OK thanks and I checked the pads today but couldn't get any info on the mfg. Both fronts and rears look like they are OEM . Lining material looks the same as do the backing plates. My days of track stuff are over so this is just a weekend driver. I don't want to put any major bucks into brake mods when I don't need it. I'm usually easy on brakes so I suspect that the present pads will last me another 30K miles. I usually get 55K on a set of pads on most of my cars except for my wife's Volvo which does about 25K. She is harder on the brakes where as most of my driving is on major roads and highways with little stop and go. Thanks for the info , enjoy the ride
     
  11. ProCoach

    ProCoach F1 Veteran
    Owner

    Sep 15, 2004
    5,465
    VIR Raceway
    Full Name:
    Peter Krause
    #11 ProCoach, Jul 5, 2006
    No question that even modern "race" compounds are a tremendous upgrade to OEM pads. On the Showroom Stock BMW's I used to race, the way we achieved an altered brake bias (as the rules prohibited altering the brake master or adding a bias adjuster) was to run the stickier (higher cF) PFC 90 compound in the front and the less grippy (different cF according to temperature rise than the fronts) PFC 83 in the rear. That's what BMW Motorsport (Milner and PTG) TOLD us to do. It worked.
     

Share This Page