Disc brake catching

coeur

Hi, i'm looking for some suggestions to solve the following problem please:

I have a new bike with disc brakes. The front brake seems to be touching something once every revolution. However, when I touch the brake lever the catching stops. It is almost as though the brake pads have some slack or play in the caliper and they are touching the rotor. As soon as the slack is taken up by touching, not pulling, the brake lever the noise stops. Can anyone relate to this and explain how to remove the 'slack' on the pads and hopefully resolve the problem?

Incidently, when I get off the bike and spin the wheel the noise is not present - I only get the noise when riding the bike?!!

Thanks

The Rookie

Yup, entirely normal, pad is still bedding in and it's likely the piston hasn't settled to its proper position yet.

02GF74

If it is a new bike then take it back to the shop for them to look at.

You don't give enough info. Are the brakes Hydraulic or mechanical?

Depending on the brand, with Hydraulic disc there is about 1/2 to 1mm clearance between pads and discs so they should not touch, on or off the bike.

Are callipers centred? Is there any runout in the disc?
Is the wheel fitted correctly and skewer tightened, this may explain the noise when bike is ridden and not.

coeur

The brakes are Shimano BR-M315, Hydraulic Disc Brakes.

How long can I expect this to continue? 50 miles, 100 miles?

What do you mean by 'run out in disc'? Will check the alignment of caliper and ensure the wheel is correctly fitted.

02GF74

Runout simply put is side to side wobble if the braking surface, ideally there should not be any.

To see this look at the outermost disc edge running in the gap in the calliper.

coeur

Thanks for explanation, I'll check this but there shouldn't be any as the bike is new.

02GF74

coeur wrote:

Thanks for explanation, I'll check this but there shouldn't be any as the bike is new.

In theory there shouldn't be but in practise it is not too difficult to knock a brake disc due to careless handling.

The wheels should spin soundlessly, except for the freehub ratchet obviously.

cooldad

Nonsense, there's often a little 'ching' from brakes, depending on the clearance. It's normal. If the brake is actually binding it's a problem.

JBA

As others have said, it’s nothing to be worried about and is highly unlikely to be a bent rotor.
If it is bothering you it may be worth realigning the caliper to try and improve the clearance between pads and rotor. Before doing that though try removing and refitting the wheel just in case it is slightly out of line.

02GF74

cooldad wrote:

Nonsense, there's often a little 'ching' from brakes, depending on the clearance. It's normal. If the brake is actually binding it's a problem.

You are obviously not trying hard enough. I have and had bikes with shimano, avid, magura and formula disc brakes, various that are set up so as not to make a sound.

The Rookie

Rubbish, they are not a robust system, many won't make a noise but a little noise is far from unexpected and 99% of the time nothing can even be done about it. Maybe try riding your bikes as well as looking at them?