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Thread: brake caliper mounting

  1. #1
    We are using a 1/4" thick mild steel plate that we plan on using to attach our brake caliper with. Each plate will be bolted to a machined aluminum upright. We are using Wilwood Dynalite Single Piston Floating Calipers on each corner. I'm just curious to see what we have to do in order to lock the threads on the floating pins from turning out of the steel plate. Do we use loctite on these threads? Or anything at all? I'm not too sure exactly how much heat is going to be radiated through the caliper to these pins but to me loctite may not be the ideal solution because of this.

    Just curious to see what other teams use on this application.

    TIA,

    Brett
    "If Speed wasn't important, it wouldn't be called the Human Race." -Saleen

  2. #2

    Join Date
    Sep 2005
    Location
    Washington University in St. Louis
    Posts
    55
    Loctite will definately weaken at higher temperatures...whether your brake calipers reach this "higher temperature" is up to you to determine I guess. Someone on here can probably point you towards finding out a strength vs. temp relation for Loctite. Loctite's High-Temp formula would be a better option. A nylock or a interference locknut would be a much better option than either flavor of Loctite. As good as Loctite is (we used to call 609 the "Hand-of-God" formula), a positive locking device (Nylock, interference nut, cotter pin, castle nut, safety wire, etc.) will is a much better choice for keeping racecar fasteners where they are supposed to be.
    And yes, use a locking device....I used to think they would never come into play until a cotter pin held on our left rear wheel at an autocross. The rules committee mandates them for a reason.

  3. #3
    For what it's worth, the nylon's good to about 250F. Forum searching tells me that uprights only get to about 150-200F. Does anyone have problems using nylon locknuts to attach, say, upper and lower ball joints?

  4. #4
    If you are looking at what kind of hardware to use, I would recommend Aircraft Spruce or Coast Fabrication.

    http://www.aircraftspruce.com/catalog/hapages/an363.php

    MS21042s will probably suit your application if I'm reading it right. I wouldn't use a Nylock or Loctite when a good nut and bolt should do the trick. If you are still unsure of the integrity of the connection, safety wire should help.
    Kettering University FSAE (99 - 03)

  5. #5
    Nice. The AN363 look like expanding type. Are the MS21042's distorted thread?

  6. #6
    Senior Member
    Join Date
    Oct 2005
    Location
    Stockholm, Sweden
    Posts
    215
    While on the subject, Formula Student Germany rules, specifically ban nyloc to secure any component of the brake system.
    KTH Racing '03-'08
    Dartmouth Formula Racing '07

  7. #7
    How much room do you have designed between the rotor and the brake caliper mount? I know for ours there's not much room. We ended up just safety wiring everything together and we had a heck of a time getting two threads to show. Now looking back it would have been nice to find a radial mount caliper and then just safety wire the heads, but I haven't found any cheap radial mount calipers either so....

  8. #8
    The caliper comes with its own floating pins which have 7/16" x 14 threads. The threads are about 3/8" long so to me that means they are meant to be threaded into a 3/8" thick plate. I'm just trying to figure out if there is any way to keep those pins tight.

    Safety wire wouldn't be too ideal since I believe it still allows the pins to loosen but not come right out. If those pins loosen even a little bit, it throws out the alignment of the caliper to the mounting tab and results in brake failure since the pad/caliper wouldn't be able to float freely.

    A locking nut would be better except we don't have enough thread to work with for this application. I do agree though, the heat may play around with the loctite a little, possibly even allowing the compound to drip onto the rotor if it gets hot enough, which isn't good.

    Once the caliper is mounted, the distance between the mounted surface and the rotor is VERY minimal so we don't have alot of room to play around with in that regards.

    Any other ideas would be greatly appreciated.

    Question: Would 6061-T6 aluminum be okay for the brake tab? I noticed a few teams machine a brake mount right on their uprights but I'm just curious if the heat generated by the brakes will compromise the integrity of the tab. Right now we are looking to make the tab from either 1/4" mild steel plate or angle iron, but still researching some ideas since we do not have 6-axis laser or hydrojet cutting available in our area which would be required to do the cuts if we make the tab out of angle iron. If we do, our only other alternative would be to throw it under a mill.

    Ideas appreciated.
    "If Speed wasn't important, it wouldn't be called the Human Race." -Saleen

  9. #9
    Senior Member
    Join Date
    Aug 2003
    Location
    Kirkland, Washington
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    369
    Nobody has mentioned that Loctite is not considered an acceptable means of positive retention. The rules regarding retaining fasteners is as follows.

    "3.7.2.2 Securing Fasteners
    All critical bolt, nuts, and other fasteners on the steering, braking, driver's harness,
    and suspension must be secured from unintentional loosening by the use of positive
    locking mechanisms. Positive locking mechanisms include:
    - Correctly installed safety wiring
    - Cotter pins
    - Nylon lock nuts
    - Prevailing torque lock nuts
    Note: Lock washers and thread locking compounds, e.g. LoctiteŽ, DO NOT meet
    the positive locking requirement.
    There must be a minimum of two (2) full threads projecting from any lock nut.
    All spherical rod ends and spherical bearings on the steering or suspension must be
    in double shear or captured by having a screw/bolt head or washer with an O.D. that
    is larger than spherical bearing housing I.D.
    Adjustable tie-rod ends must be constrained with a jam nut to prevent loosening."
    Josh Gillett
    Oregon State FSAE '04-'06

  10. #10
    We've used investment cast uprights for a number of years which have an integral caliper mount. The material is a casting alloy which is quite similar to 6061, and we've had no problems as regards loss of strength etc on the caliper mount. The items get regularly crack-checked etc so I would hope we'd have picked up any problems.
    Alastair Clarke
    Cardiff Racing
    CARDIFF UNIVERSITY, UK
    www.cardiffracing.com

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