Front brake noise (all the damn time)

[Tsopo]

A few days ago it started suddenly and I've no idea why. There's a noise coming from the front disc/pad. When in motion (not braking) there's a loud, scraping sound. However, there's also a knocking sound that increases in frequency the faster the wheel turns, and which is more audible when cornering.

When I apply the front brake both noises stop. Unfortunately, at low speed they are replaced with a generally shitty sound, which is more noticeable when I brake firmly. I know that's a vague explanation, but it's the only way I can describe it; it's as if there's a whole load of rubbish on the pad or something. At very low speed I can feel excess vibration when I brake.

Does anyone know why this may have started? And more importantly, what to do about it? Nothing has happened to the bike (03 Varadero), certainly not since I've had it. And as I said, it started very suddenly a few days ago.

If I need new pads, it's something I'd like to do myself as I want to learn as much as I can about the bike (and bikes in general). I wouldn't want to take it to a garage unless it was a severe problem.

Any advice would be most appreciated

[bacon]

if your worried about the pads, why not remove them and have a look at them?

There will be a pad cover or something similar which you will have to remove, either small screws or allen key headed bolts to take it off.

Then the pads are usually held in place with a pad pin that will have a small circlip or something stopping it from coming out of the caliper, pull the clip out, slide out the pad pin. then pull the pads out, if they are knackard or worn below spec then get some new ones.

its a simple 5 minute job so dont worry if you havent done it before.

Worst case is they are very dirty and the pads are a bit stuck in, in which case you may need to unbolt the caliper from the fork leg to get the pads out.


When putting the pads back in, give the back of them a good clean, then apply some copper grease to the back, will stop noise coming from vibrations against the piston etc, and will also prevent siezing

edit: Just a thought, while you have your pads out take a look at the pistons, if any of the pistons in your calipers have siezed up that could be contributing to the excess noise, in which case you would need to rebuild your calipers (piston removal), potentially new seals etc, but thats a fun job hehe.
What can happen is that months of salt from the roads etc can get behind the dust seal and into the groove, causing corrosion etc, this pushes the dust seals into the pistons which can lead to the seals being dragged out with the piston and causing it to become very stiff and seize up.

But yeh see what the pads and pistons look like first, may give you some insight to whats wrong, good luck

[MarkJ]

What bacon said. Also if your calipers are sliding ones, separate the caliper and sliding pins and regrease it all so the caliper moves freely.

As you get this noise every revolution of the wheel your discs could be warped (by having seized pistons, as above). Take both calipers off the discs and hold them away from the wheel. Then spin the wheel and whilst looking at the discs from the front, see if they run true, or wobble in and out. If they wobble in and out you need new disc(s)

[ZRX61]

[Lycan]

I have cured sticking pistons without stripping down the caliper.

I removed the pads and expressed the pistons slightly, but not enough to pop them out of their housing.

I used a thin piece of wood to prevent the pistons from travelling too far. I based this on the thickness of the disc, plus the thickness of the pads minus the braking surface.

Once the pistons were exposed far enough, I cleaned around the outside of the pistons, pressed them back into the caliper, put the pads back in and it worked perfectly.
____________________
From sunny sussex, Hove actually, down on the coast
Current bike a rather tatty CBF500 which is used and abused. 60k on the clock so far.
Commute every day up to the smoke, so the miles add up pretty quickly.

[Tsopo]

Cheers for the replies. I'll follow the advice and have a look, although I'm a little worried that it may be a bigger issue than my newb mind understands

If it is a warped disc, how would that have happened so suddenly, without anything 'bad' having been done to the bike (i.e. dropped, crashed)?

[Digit]

Discs warp from overheating, it sounds to me, as has already been suggested, that you have worn all the pad friction material away and are now braking on metal to metal.
Routine checks and maintenance tend to be cheaper than subsequent repair work.

Roy.
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Happy daze!

[Lycan]

I've had a couple of warped brake discs in the past. Usually the cause is the disc overheating because the brake is binding as the result of sticking brake calipers.

Because of dirt or debris on the shaft of the piston, the brake is continuously pressed against the disc, not able to be fully released.

You would probably notice if this was the case though, because the bike would be harder to push around without the engine.
____________________
From sunny sussex, Hove actually, down on the coast
Current bike a rather tatty CBF500 which is used and abused. 60k on the clock so far.
Commute every day up to the smoke, so the miles add up pretty quickly.

[Tsopo]

Yeah that's the case now. It's very subtle, but it's definitely a bit harder to push.

[Lycan]

Don't know if your bike has a center stand or not.

If it does, put on center stand and see which wheel is sticking.
If not, put on the side stand, get a friend to push each wheel in turn off the ground and check which one is sticking.

I usually find it easiest to take the pads out if the caliper is unbolted from its mountings. Make sure you slacken off the brake pad mounting first though, because otherwise you have to try to hold the caliper still while undoing that bolt.

Also make sure you don't push the brake piston too far out because if you do you'll get brake fluid everywhere and need to get the brakes bled. Try using something like an old toothbrush to clean the sides of the piston.

If this doesn't work and you aren't confident in your abilities you might need to take the bike to a dealer to get the brake caliper serviced.
____________________
From sunny sussex, Hove actually, down on the coast
Current bike a rather tatty CBF500 which is used and abused. 60k on the clock so far.
Commute every day up to the smoke, so the miles add up pretty quickly.

[Paxovasa]

Could also be like mine and that is the floating part of the disc has movement from the bobbins.

That will explain the knocking noise and also why you feel a pulse through the brake lever when pulling gently on the front brake, it will also explain why when you brake more forcefully that it stops
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Suzuki GSF600 K3 (in the fastest colour, black).

[Tsopo]

[Tsopo]

It was just the pads, thankfully. My neighbour tried to fit the new ones, but one of the pins on the caliper had been tightened too much, and with the wrong tool, so the end had rounded off. Had to take it to a mechanic today to get it out...changed it in 20 mins, charged me £36, including the parts.

I embarrassed myself by taking along the wrong pads though. Bought them off ebay and they were for a bloody Kawasaki! Christ, I'm a dumb arse newb if ever there was one. The ad said they were for a Vara, but had I any sense I would have checked before hand.