Disc brakes

[Crankarm]

The rear disc brake on my Kona Kula - Hayes Stoker hydraulic is making one hell of a racket when I apply it and creating massive vibration which transmits right up the seat post .

Could it be that the wheel is not straight/true in the rear dropout or are the pads likely to be the cause? The pads (and bike) have covered very few miles, but the pads had I thought bedded in. The pads were squealing last week. When holding the bike, off it and stationary, the pads would whine with even the slightest movement of the bike, sounding like a rusty old pub sign or gas station sign in need of oil in an old American movie. I have adjusted the sit of the wheel in the drop outs so this whiny metallic noise has now gone, but as I say now when I use the back brake, doing so creates one hell of a racket and vibration, a bit like a double decker buse whose brakes are fecked making one hell of a lot of noise coming to a stop.

Any constructive advice would be greatly appreciated.

C.

 

[2Loose]

Have a go at centering the caliper by loosening the bolts holding it to the frame. Then spin the wheel and squeeze the lever hard two or three times before clamping the lever hard and tightening the caliper bolts back up again.

Normally works for me and takes 2 mins.

 

[Pauluk]

My disc brakes are always squealing, I've just about given up worrying about it now. If I clean the disks with Halfords brake disk cleaner then there's a bit of improvement for a short while. I'd like to buy some new pads to see if I can get quiet brakes but I don't know what to buy/try.
The vibration is a new one though. I would check that the brake disk is running true through the caliper. Could something like a piece of grit got onto one of the pads.
Sorry, not mach help but I would be interested to know if and how you solve it Crankarm

 

[I like Skol]

I put up with this kind of problem on and off for over a year and 3000 miles on my hybrid which had Tektro (Aigura?) hydraulic brakes. Eventually got fed up of continuous adjustment, cleaning and variable stopping performance (not to mention the noise when damp!) so bought shimano XT set but kept the original rotors. Must be about 6 months now and have hardly had to touch them, reliable and impressive stopping performance also normally quiet even when wet (still the odd squeal but not bad at all. I know exactly what you mean about the old bus brake vibration. Mine was so bad I was almost afraid to use the brakes when it was at it's worst for fear of shaking the bike apart and shocking other road users with the noise.

 

[Cubist]

Crankers, it sounds like you haven't got the wheel true in the dropout. If you moved the wheel to get the brakes centred as you explain, then you have moved the mountain rather than Mohammed.
Put the wheel back in the dropouts and centre the caliper as 2Loose suggests. Once you've centred it , check the rotor for warping or excessive runout by putting the bike in a stand or upside down and spin the wheel. Get a light source behind the caliper and watch for movement between the pads and the rotor. A small amount of runout is normal and acceptable as long as it is less than the gap between the pads of course.
If it is bent use a pair of long jawed adjustable grips or an adjustable spanner to gently bend it back into shape. If that doesn't fix it get a new rotor for a tenner from Superstar or Bikefridge on Ebay.

 

[MacB]

As has been said and this is the routine I'd follow:-

1. remove disc brake caliper from frame
2. mount wheel properly and satisfy your self it's running correctly
3. I then mount the caliper adaptor, if your brakes aren't post mount, on its own.
4. spin the wheel and compare the rotor to the edge of the adaptor, this was how I discovered that one of my disc mounts wasn't quite square, it also tells you if you're rotor is out of true and is much easier to see than with caliper mounted
5. use spacers to straighten the adaptor alignment, and/or true the rotor, both of these are easy to do. You can buy little packs of spacing washers for the adaptor if needed. Lots of tools will work to true the rotor, including gloved fingers, but I treated myself to a proper one and it is easier and quicker with it. Though you may not have three clumsy sons to maintain rotors after
6. remount the caliper and go through the setup process as normal

The above should only need to be done the once and should save you chasing down other ideas when it's a basic setup problem. After that it's the usual checking the rotors and pads aren't contaminated and, most importantly, the pads retract properly. The next step would be different pads, I've had good luck with Superstar sintered ones and they are much cheaper than OEM.

 

[Crankarm]

Every one - thanks very much for your advice. I am going to take a good look at the bike later in the week bearing in mind all that has been writ here and hopefully sort the problem out once and for all.

Thanks again.

C.

 

[Crankarm]

Update. Rear wheel ok now lots and lots of rain have had a beneficial affect. Front wheel not so lucky. Very careful positioning of the front wheel in the dropouts minimises pads squealing. I have to take front wheel off and put back on a couple of times a day to get the bike in and out of my car so a bit of a chore. Some times it takes numerous attempts to centre before rubbing and squealing finally stops

 

[Red Light]

Couple of extra tips to minimise squealing. Take the pads out and chamfer the leading edge and while they are out take a dobb of copper grease and put it on the back of the pads before you put them back.

Be careful with the squeeze the brakes and tighten the mounting bolts alignment method with hydraulic brakes as both brake pads move (unlike cable discs) and you can end up with them well away from centred. Instead look visually at the centring of the rotor in the caliper housing and move it until you can see equal clearance of the brake pads on both sides and the pads are parallel to the rotor with the brake lever released. Its a bit of a faff getting it right but it will solve most of your problems with rubbing and squealing.

 

[lpretro1]

It is always best to get the brake mounts on forks and frame faced to ensure they are flat to start with. Any decent bike mechanic should be able to do this for you. Once done then refit brakes and recentre caliper as advised above. Have you checked the rotors for correct thickness as well - they do have a limited life? A new set of pads may cure it. However, some makes/models of brakes just damn well squeal no matter what.