Newbie new bike brake question

waynehorne
waynehorne Posts: 5
edited May 2014 in MTB workshop & tech
Hello. New to the forum so thought id say hi first of all. Now on to my query...

I recently bought the Voodoo Bantu from Halfords (full price because I'm a fool) and because I was like a small excited child I was at first ignorant to the fact that they seemed to rush building the bike and didn't really set it up for me. Now as soon as I got it home I noticed a grinding noise from both brakes and remembering a little from when I used to bike over 6 years ago I assumed it needed it's callipers aligned so I had a fiddle with aligning them and sort it, or so I thought. Now I've been on three rides and every ride I have noticed that I get grinding coming from the front brake while braking slow (maybe bedding in?) BUT I also get the noise while riding at high speed without braking. I am very reluctant to keep fiddling with the callipers and wondered if there's something else it could be. I still have a 6 week free service there but thought if it is something I can do myself it will be worth it for the knowledge and experience alone. Any help would be awesome! Much love.

Comments

  • bailsofhay
    bailsofhay Posts: 191
    Loosen the caliper mount bolts, clamp down on the brake lever and re-tighten the bolts while keeping the brake pressure on. Get them bedded in while braking at speed (safely).
  • nicklouse
    nicklouse Posts: 50,675
    And the brakes are?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • bailsofhay
    bailsofhay Posts: 191
    They all come with hydraulics at the moment as far as I can see. Though I am assuming that is what the OP has.
  • waynehorne
    waynehorne Posts: 5
    Tektro hdc-300 Hydraulic discs. :)
  • waynehorne
    waynehorne Posts: 5
    bailsofhay wrote:
    Loosen the caliper mount bolts, clamp down on the brake lever and re-tighten the bolts while keeping the brake pressure on. Get them bedded in while braking at speed (safely).

    I've used this method three times before I noticed the sound. Which is what is making me think it really be that? It was constant but after aligning them with this method I managed to get rid of it only for it to come back and hifh speeds. I did take the wheel off to put it in the car so is it possible I may have reattached it wrong? I did double check at the time and seemed fine but...I am a major newb!
  • bailsofhay
    bailsofhay Posts: 191
    Can you visually check the alignment? Is the wheel properly seated in the dropouts? After doing the above method slowly rotate the wheel watching for the pads touching the rotor, the pads shouldn't touch the rotor unless braking. It's possible the rotor has been damaged in transit at some point and is slightly bent.
  • waynehorne
    waynehorne Posts: 5
    bailsofhay wrote:
    Can you visually check the alignment? Is the wheel properly seated in the dropouts? After doing the above method slowly rotate the wheel watching for the pads touching the rotor, the pads shouldn't touch the rotor unless braking. It's possible the rotor has been damaged in transit at some point and is slightly bent.

    It doesn't touch when normally spinning the wheel. It appears to only happen with weight on the bike and at a fast speed. That's what is making it a rather strange case. Spinning the wheel by hand as fast I can I barely get any noise if at all but when I'm cruising down a big hill it starts intermitently grinding. I'm 90% sure it's coming from the front however with concerntrating on riding I could be wrong.
  • bailsofhay
    bailsofhay Posts: 191
    Hard to diagnose noises that only occur when riding at speed. Do they still retain stopping power when this is happening? Its not unusual for brakes to make noise but grinding doesn't sound good. Might not be the brake at all could be the hub. I had a periodic squeak from the front that used to drive me crazy when turning or leaning to one side while going fast. I could never figure it out and it eventually went away. ( not to say you should leave it and see what happens if you are worried)
  • kajjal
    kajjal Posts: 3,380
    If you take the wheel off a bike with disc brakes it can rub if you don't put in back into a very similar position. You have tried the right adjustment but try doing it again by eye making sure the gap between pads and rotor is the same both sides. My old elixir 1 back brake had a slightly uneven action which mean unless set by eye it would rub. My new XT brakes and my wife's SLX brakes don't have this problem.

    Also check the rotors are done up tight enough as well as your QR. If it only happens at speed this suggest the increased stress at speed is causing the problem in sone way.

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