Troubleshooting disc brake power issues

Jimfrandisco
Jimfrandisco Posts: 210
edited October 2012 in MTB workshop & tech
I recently bled them (Hayes Stroke Trail) and they have new pads - at slow speed its easy to lock wheels up etc, but as soon as i get up any speed its a problem.
If i haul on the brakes for a complete stop they're not too bad, but there's no subtlety to them - if i want to just scrub off a little speed entering a corner for example they don't do anything.

So is that purely down to requiring a proper bleed, or could it contaminated pads and rotors that are the issue - is there any trouble shooting that people can recommend for finding out?

Thanks in advance

Comments

  • nicklouse
    nicklouse Posts: 50,675
    how does the lever feel?

    nothing you have said yet indicate the need for a bleed.

    why did you bled them before? did you do it with the old or new pads in?

    what did you use to clean the brakes?

    have you bedded them in yet?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Jimfrandisco
    Jimfrandisco Posts: 210
    Lever i'd say feels 'normal' - as in there's no indication there of a problem, not spongy, not pulling right back to bars etc

    Bled previously as lacking in power - bled with no pads in, just spacers then new pads in.

    Cleaned calipers with just soap/water and without the pads in - haven't cleaned rotors with anything other than water to avoid leaving any residue

    Bedded in ok - much to the strange looks from my neighbours.

    thanks

    Jim
  • The Rookie
    The Rookie Posts: 27,812
    Calipers centred OK? watch the caliper carefully when applying the brake stationary, are the pads moving too far (compare to front), is one moving before the other, can you see a gap one side only?
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • nicklouse
    nicklouse Posts: 50,675
    Jimfrandisco wrote:
    Lever i'd say feels 'normal' - as in there's no indication there of a problem, not spongy, not pulling right back to bars etc

    Bled previously as lacking in power -
    if lever feels normal then no bleeding will change anything.

    Bleeding due to a lack of power will not bring the power back.

    all a Bleed does is remove air from the system and reduce the spongyness of the feel ( and lever moving to bar without moving pads).

    so you have other issues.

    i sugest getting some brake cleaner and cleaning everything again. and new pads.

    some soaps contain conditioners. bad for friction.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Jimfrandisco
    Jimfrandisco Posts: 210
    Thanks for that - disc brake cleaner rather than alchohol?
  • cooldad
    cooldad Posts: 32,599
    Isopropyl alcohol. Not disc brake cleaner.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools

Categories