Hydraulic disc brake freak out

[Mollyharris]

Hi, just wondering if anyone could help me with a problem I have had with my voodoo MTB the front hydrolic disc brake when pressure is applied when riding makes a sort off popping clicking noise which you can feel bumps theough I’m sure it’s coming from the calliper I have tried realigning the calliper but I can’t seem to fix it, i attached my video for reference of the sound

https://youtu.be/MnEaaYEfpyY

[tim-b]

Hi
If you can feel the brake pulsing either the disc isn't running true or the surface is dirty.
Spin the front wheel with something rigid taped to the fork to touch the disc and watch/listen; the discs are thin (make sure that it hasn't worn too thin) and are easily bent. A gentle tweak with an adjustable spanner might true it up
Give it a scrub with a pan scourer to remove any dirt
Regards
tim-b

[yostumpy]

Disc brake discs used to be deeper, i.e. the surface of the disc that the pad touches , used to be equal to the depth of the pad. Now, in an effort to save weight, be more fashionable, and also suit all makes of calliper/ pad without excess weight, the discs are shallower, and often shimano type pads overlap the braking surface and the pad then also uses the spider arms for braking. So I'm guessing the clicking / pulsing is the edge of the pad binding on each spider arm as the wheel rotates, nothing to worry about but annoying. Mine did it, then I swapped discs and realigned the calliper so it was parallel to the disc. Slacken off adjusters, undo 2 clamp bolts until calliper moves freely, apply brake and use toe strap / zip tie/ string around the lever to hold it on, wiggle calliper and do up 2 holding bolts, then adjust the pads again. Hope this helps. You can buy basic shimano drilled discs that are deeper, about£6 each, but they won't win any prizes!

[Brucey]

if there is a mismatch between the pad and the disc (so that the pad is overhanging the Outside Diameter (OD) or Inside Diameter (ID) of the braking track, this needs to be resolved.

There are two main sizes for pad depth (radial dimension); narrow ones and wide ones, being about 15mm and 17mm respectively. The one combination that you must not use is narrow discs with wide pads. If you use a matched set and they overhang, it simply means that the system is not correctly aligned. If so, you can address this in two main ways;

1) adjust the caliper mountings so that the caliper is correctly aligned. This can be as simple as loosening some screws but it can require fiddling with spacers or even be impossible (if the frame is badly made).

2) dress the brake pads. If you can't adjust the alignment as per above, then grinding the overhanging material from the pads will help avoid future problems.

If the overhang is on the ID then you can get noise and the disc spokes will wear prematurely. If the overhang is on the OD then braking can be unpredictable; when the disc is very hot the brake may be a bit grabbier than normal (because the pads bear against the disc in an abnormal fashion) and more worryingly the lips that are left on the pads can (once the pads are each worn by half the disc thickness) actually touch one another. This results in an instant reduction in brake force. In fact the brake can stop working altogether.

[Mollyharris]

Thank all for your responses I’ll try everything recommended and get back to you all

[nigelnightmare]

WELL...….

......Update please!
What was causing it?

[gxaustin]

Thanks for bumping this - I think I have this problem with my TRP cable hydraulics. I shall investigate

[Mollyharris]

Still the same, cleaning up the pads helped but no really big improvement sorry

[Brucey]

might it be the hub bearings failing?

cheers

[Mollyharris]

Not sure how could I check that with out it being too complicated ?

[LinusR]

Having watched your video with the sound turned up quite loud it just sounds like the pads might need cleaning or replacing. The sound is not unlike the sound coming from my Voodoo MTB with hydraulic brakes on occasion (usually after being splashed with water, mud or dust). Carefully take the pads out and rub the braking surface on some sand paper. This video shows how to clean the pads https://www.youtube.com/watch?v=4MBhhczBUhA

[Brucey]

Not sure how could I check that with out it being too complicated ?

with the wheel out is the axle free to turn and smooth-running? Does the wheel spin freely and smoothly in the frame? (adjust the brake pads out of the way if they are rubbing slightly).

This will give you a clue as to the condition of the hub bearings (if they feel bad then they are bad and you need to something anyway, but they might feel OK and still be bad in fact, or be bad and not cause the problem you have...).

It is still most likely a brake problem of some kind but one shouldn't be blind to the other possibilities.

cheers

[hamster]

A daft one, but have you checked that all the brake rotor bolts are tight?

[Marcus Aurelius]

It sounds like the pads are starting to get worn down, and the rotor vents are catching the spring that pushes the pads back. Get new front pads, all may be fine again.

[Mollyharris]

Thanks for everyones reply’s

Hub bearings seem to be running smooth, going to try replacing my pads