Brake advice for Street/AutoX/Track

Discussion in 'Fiesta ST Chassis Upgrades' started by jordbird, May 15, 2015.

  1. jordbird

    jordbird New Member

    I read through everything I could about FiST brake upgrades, but wanted to share my situation in hopes of clarifying my options. I attended a race school this past weekend in my bone stock 2014 FiST and was on track for 7 sessions progressing in time from 15-35 minutes and progressing equally in intensity. 20 minutes into the last session my pedal went soft so I babied it through 2 easy laps and it felt 60% firmer but still soft, so I pulled into the hot pits and let the car cool for 10 minutes. Back on track for a few more laps and the brakes never felt right again, a bit soft, not grabbing as hard, mild vibration in the first 1/2 of brake application.

    For the last week of street driving the pedal has felt the same, slightly softer, not grabbing as hard, mild vibration in the first 1/2 of brake application. I checked the pads and there is plenty of material left, the rotors feel a bit scarred but not that visibly bad. Here are what i think my options are because I plan on doing at least 2 more track days and a few autox sessions this summer. I plan on flushing with race brake fluid regardless.
    1. Replace front rotors with OEM and be more mindful during my future track sessions.
    2. Replace front rotors with Stoptech slotted and a set of new OEM pads and go nuts on the track.
    3. Machine rotors (although I don't think this is a good idea)

    Any advice on what is has likely happened would be appreciated, I know I am not the first to face this conundrum.
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  3. Chuckable

    Chuckable Member

    I've been through something very similar, and think that you're on the right track based on what I've read as well. Definitely change and upgrade the fluid no matter what you do. I was always taught that rotors warp when overheated, and then machining the rotors (within acceptable limits) will solve the problem. Recently though, I've read that in a situation like yours it probably uneven pad transfer onto the rotors as a result of overheating that's causing the vibration. New upgraded rotors and pads (I've heard good things and will be buying, Carbotechs) along with new fluid and you should be good to go!
  4. haste

    haste Member

    Brakes are VERY important especially at track speeds. I advise not to skimp on brakes.
    For the track I used hawk dtc-60 pads on the front(stock rotors) and kept the rears stock. I flushed brake fluid and put in torque rt700. I also removed the stock dust shields on the front and the brakes survived 8 sessions 20-25 minutes each. I was able to reuse my rotors and put the used OEM pads back on without issue. I'm still using the torque rt700 that was run on the track and the brakes feel great on the street. I plan on going back to the track in October and will probably put some fresh rt700 in.

    Some good info here:

    I wish I had calipered my rotors and pads before and after my track sessions but I didn't think about it at the time. I will definitely be measuring everything come
  5. jordbird

    jordbird New Member

    Thanks for the input guys.
    "uneven pad transfer onto the rotors as a result of overheating that's causing the vibration"
    Over the weekend I found an empty rural road and once the brakes got up to temperature, did a procedure to bed the pads/rotors again to try and remove excess material on the rotors causing the vibration. It worked, brakes feel much better now and no more vibration.

    I am going to buy an extra set of front oem rotors and a couple sets of pads for my next track weekend, make sure I am well prepared.
    Mr UFO likes this.
  6. Chuckable

    Chuckable Member

    Thanks for the feedback! Glad it worked for you.
  7. Michael Casavant

    Michael Casavant New Member

    While I haven't swapped out brakes on my ST yet, I have had years of experience with my RX7 on track (and before that a MS Protege).

    A few things to note:
    1. When switching pad compounds, always switch brake rotors. Don't turn them. Don't re-bed them. Replace.
    Brake pad materials are not usually compatible between brands and may result in accelerated pad/rotor wear and/or poor brake performance (fade, braking distances)

    One point here - Carbotech brakes are designed to be swappable. You can use XPS10's on track and then switch to Bobcat's for street while using the same rotors.

    2. Slotted/crossed drilled rotors do nothing for you, don't waste your money.
    Slotted rotors were designed to vent gas build up from under ORGANIC pads. You don't have organic pads, you have semi-metallic (if stock).
    Cross drilled rotors were designed to dissipate heat, you won't run into heat issues on a 25-30 minute session (if you use a good brake fluid).
    Cross drilling and slotting reduces total capacity because it removes a significant amount of material (which could be an issue in a 25-30 minute session).

    3. Replace your brake fluid with a fresh, good quality DOT4 (not DOT5)
    This has a huge impact on capacity. Your pads and rotors can usually take the heat, but the fluid boils and absorbs water - further reducing brake feel/capacity. Ever notice the wet and dry boiling points on brake fluid containers? You will now...
    RBF600, ATE Super Blue or Motorcraft DOT 4 - something like that

    4. Start to get fade on track? Bleed your brakes between runs
    Can't say this enough - fading brake fluid will never get better, only worse, until it fails completely.

    If you really want a deep dive into brake technology (which completely explains why "warped disks" are not really warped at all), Stoptech made an awesome white paper explaining all sorts of things about brakes, search Google for "stoptech technical-white-papers warped-brake-disc-and-other-myths" (sorry, I can't post links yet)
    Last edited: May 22, 2015
  8. Ca5p3r

    Ca5p3r Member

  9. jordbird

    jordbird New Member

    Thanks for all the good information. I spoke to soon and the mild vibration is back. I am going to replace the front pads/brakes/fluid with fresh OEM and do a proper break in in to ensure longevity.

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