Author [NL] [FR] [ES] [DE] [SE] [IT] Brake Service  (Read 8572 times)

0 Members and 1 Guest are viewing this topic.

  • Offline Novocastrian   gb

    • Trophy Master  ‐    713
    • ****

    Offline Novocastrian

    • Trophy Master
    • ****
    • Posts: 713
    • Bike: TTSE
    • City / Town: Tynemouth
    • Country: gb
    Re: Brake Service
    Reply #24 on: Sep 26, 2022, 05.31 pm
    Sep 26, 2022, 05.31 pm
    *Originally Posted by GarminDave [+]
    UPDATE September 2022.

    Any input from you guys?

    For the first time ever,  during my recent big trip and at 16,000 miles on original discs,  I definitely felt vibration from the front end under heavy downhill braking.


    Ken Hastie
    TTSE, a handful of BSAs, a Vespa 300 and an MGB

  • Offline Coconut   gb

    • Trophy God  ‐    10202
    • *****

    Offline Coconut

    • Trophy God
    • *****
    • Posts: 10202
    • Bike: 2017 Trophy SE
    • City / Town: South Birmingham
    • Country: gb
    Re: Brake Service
    Reply #25 on: Sep 26, 2022, 07.47 pm
    Sep 26, 2022, 07.47 pm
    Garmin Dave :

    If EBC are saying the Discs are within specification ( Triumph specify a maximum run out of 0.15mm ),
    then it might NOT be the Discs that are causing the pulsing, or vibration when braking.  :084:

    It could be due to wear in the front wheel bearings,
    the Headstock bearings could need adjusting or be worn,
    or it could be due to uneven wear / scalloping of the front tyre.

    As has been mentioned many times throughout the Forum previously, it is SO
    difficult to check whether the Discs are actually "warped" or whether, because of their
    Semi-Floating design, they are "just" not running true to the rotation of the wheel.

    The Service Manual description of checking is, in my opinion, pretty much useless :
    "Measure disc run-out using an accurate dial gauge mounted on a surface plate".  :027:

    With the Disc on the bike, a dial indicator can show fluctuations when the wheel is rotated,
    but how do you know whether this is because the disc is warped, or because the disc is not running true ?

    Take a look at this exaggerated drawing, looking end on at a ( red ) Disc not running true,
    with the black rectangles representing the Brake Pads.
    When rotated through 180 degrees, the position of the "High Spot"
    indicated by the top pair of arrows, would become the Low Spot,
    even though the Disc is perfectly flat !

    You can't take the disc(s) off and lay them on a Surface Plate to check,
    because of the design - with those "Bobbins" standing proud of the disc surface.

    I would suggest that if using a Dial Gauge, the Bobbins are all cleaned and freed off first,
    and then, when the wheel is rotated with the Dial Gauge plunger against the disc surface,
    carefully note and mark the position of any "High Spot" on the disc,
    and then see where the "Low Spot" is - If it is 180 degrees / opposite the High Spot,
    this could well indicate that the disc is not warped but is running out of true, as in the above image.

    It may be possible in such a case to gently push the disc back until it runs true.
    ( Taking care of course not to make things worse !  :138: )

    Another option is a few heavy applications of the front brake to try and do the same thing.
    In either case note the readings for the high and low spots on the dial gauge,
    so you can compare before and after and see if it has had any effect.

    Of course the disc(s) COULD be warped, and especially if there is a High Spot
    with a Low Spot that is NOT directly opposite it, or with only a High Spot / High area,
    and the rest of the disc being even, this would indicate that the disc IS warped.

    Cheers  :821:

    Last Edit: Sep 27, 2022, 09.26 am by Coconut