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Track car brake change

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  • Track car brake change

    Worked on the track car brakes recently before a track day at Knockhill.

    The plan was to keep the hard lines up front and fit standard HEL flexible lines from body to strut.
    Replaced front pads DS2500
    New front 314 discs QHBDC4788
    Started on the fronts but straight away I hit a problem as solid lines were seized and refused to come out without a fight.

    twisted lines.JPG
    ​​
    Luckily I had bought a set of HEL long flexible lines to replace the ageing ones on my other car so I scrapped the hard lines and fitted them instead.
    When changing discs and pads on the front right I found I had a leaking CV boot so got local replacement to get me going
    IMG_8760.JPG
    ​​ front complete.JPG

    With fronts sorted out went to the rear which has URS4 Calipers and the discs which are machined down to 280.
    Planned to leave the discs on and replace the pads and hoses.
    The rear HEL lines I have are for standard s2 calipers and the URS4 calipers appear to have a deeper recess so the hose fitting bottoms out before sealing inside on the wedged face.

    IMG_8765.JPG hoses.JPG

    I ended up keeping rubber hoses for now and replaced pads with Drivetec 646VG0082.
    Changed the fluid to Motol 660 and bled the clutch.
    IMG_8754.JPG IMG_8691.JPG
    Brake performance is brilliant with only a couple of issues.
    When I fitted dual brake booster I removed the OEM bias valve and with the worn setup and working ABS I never had a problem.
    After fitting pads and changing fluid I spun out a couple of times on the track
    Reviewing track footage I found that the ABS warning light had come on, the rears had locked up and I did a 180 into the gravel.
    To prove what I had seen in the video I went out for a test with the ABS switched off and with hard braking the rears locked up real fast.
    So, I have bought a balancing valve to fit to try and eliminate lock up at the rear.
    However I also have a some sort of intermittent fault with 3b ABS?
    Last edited by sjw185; 15th March 2020, 20:34.

  • #2
    Yes you definitely need a pressure compensation valve on the rear circuit!
    Panthero Coupé quattro 20vt
    Indigo ABY coupé
    Imola B6 S4 Avant

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    • #3
      Got one to install, not sure if going to fit in engine bay or in passenger floor tapped into line traveling to the rear.

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      • #4
        If it’s a track car I’d get one of the lever type adjusters and install in the cabin so you can tweak for the conditions
        Panthero Coupé quattro 20vt
        Indigo ABY coupé
        Imola B6 S4 Avant

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        • #5
          Originally posted by Error404 View Post
          If it’s a track car I’d get one of the lever type adjusters and install in the cabin so you can tweak for the conditions
          Looked at level type but was not sure on operation so got this one.


          brake bias valve.jpg

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          • #6
            It's a pity that the most pics aren't visible...
            photobucket SUCKS
            sigpic

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            • #7
              Originally posted by M_GORDON View Post
              It's a pity that the most pics aren't visible...
              Yea dont know what happened as reduced them and posted as normal?
              Had an issue with the preview, would not load before posting?
              Will try and fix it

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              • #8
                Checked out installing the bias valve in passenger floor but the best place between pipe clips turned out to be in the support for the seat.
                Decided to fit it at ABS unit and keep the original pipe intact to make sure it would actually do the job.
                Made a quick bracket to keep it steady.

                IMG_92411.jpg IMG_9242.jpg

                After bleeding the back brakes took it for a test with bias valve at full pressure and ABS off ,
                Right enough still locking up mostly rear left.
                Adjusted until under hard braking was more neutral and only under emergency stop with no ABS the fronts locked up.

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