That CLUNK sound when braking...

[FlyingDutchMan]

I've finally figured out what the occasional clunk sound is when I brake. I've worked it out by holding the front brake on and pushing the bike forwards and backwards - you can see the front disk moving on its mounting things by the pins (I dunno what its called). Now I realise there is meant to be *some* play there for heat expansion etc... but how much is too much?

Just for clairty: (not my bike) The movement is where the pins are (circled in red)

[Motoracer]

You shouldn't have noticable play on road bikes really. I'd say it's more the sign of wear and tear.

For race bikes a bit of play is normal as they have to endure higher working tempretures than road bikes but you can normally tell when there is too much play cause you'll be able to move it back and fro and side to side then.

If the buttons (pins) on the discs are too worn, you can have them replaced.

[bugjuice]

'Floating discs' and 'floating calipers'.. not sure what the tollerances are, but as long as you can only hear it and hardly see it when you throttle it by hand, you should be ok. My CBR250 failed it's WOF cos the tester knew Jack about bikes, so the minimal movement in the discs made him panic. Cost me $400, so be prepared for that. If you're not sure, best to be safe than sorry - head to a reputable bike shop (may be a Honda biased one, so they really might know their stuff) and ask them to check over. I'm sure someone here could recommend someone, or even have a look themselves for you.
Wouldn't be overly paranoid, but get them checked either way. It's often just wear and tear sort of stuff, or can be if the bike has had a hard braking life, the expansion from heat under braking hard, then cooling, then braking hard etc for a long period in its life can have an effect like this too

[Mr Skid]

The Moto-X Spec was originally a '89 CBR250R, and I've found the same problem.

Are you sure it's the rivets? I'd been told it was due to freeplay on the pads within the calipers. I originally thought it was the steering head bearings, but have had them checked out, and they're ok.

If you're clunk is the same as my clunk I'd be worried if it was from the disc/rivets..

edit: How many k's have you got on your bike? If you need to replace them I could sell you mine, I'd throw the rest of the bike in for free.

[gav]

head to a reputable bike shop (may be a Honda biased one, so they really might know their stuff)
In Christchurch? yeah right.......

[TwoSeven]

You have a semi-floating disc. If the clonk happens when you squeeze the brake lever - likely that your pads are worn and/or someone has removed the anti-shudder plate from the brake caliper. Its the steel plate that sits on top of the pads and stops them going 'clonk'

What happens is the pads sit back against the piston and snap against the disc when you hit the brake lever - so you get a loud clonk. Its not really a problem, just means there is a bit of free play.

If its a squeal, there is a similar plate that sits behind the pads and stops them moving back and forth - or you have excessive glaze.

[John]

Yes as said it is originating from the pads that would be the best bet, I would either check them and if they are fine then you have no worries, also might pay to clean out the calipers as they may have filled with crud and the pistons are sticking which are causing the clunk.

[FlyingDutchMan]

Nah its definitely the button thingies - I can see the disk move by about .5mm when I push the bike backwards and forwards with the front brake on. Oh well more money to throw at the bike. I was thinking of getting a new front end with USD forks and twin disks (stoppies!!), but I think I'll settle for cleaning the whole system out, new piston seals, lines, pads and and disk. Ahh hell its not even going to be remotely cheap whichever which way I do it.

[Marmoot]

I recommend getting your steering head bearing and tripple clamps assembly checked too.

[FlyingDutchMan]

I recommend getting your steering head bearing and tripple clamps assembly checked too.

Nah - I thought it was those for a while, but theyr'e rock solid. Checked by clamping rear wheel in place on a bike jack and trying to move the front end - and it doesn't move the slightest.

[HDTboy]

Mine does the same thing, it's definately the rivets, my mate has an RR as well and his does it too, I'm not too concerned about it really as I'm up for discs and pads soon anyway

[WINJA]

I've finally figured out what the occasional clunk sound is when I brake. I've worked it out by holding the front brake on and pushing the bike forwards and backwards - you can see the front disk moving on its mounting things by the pins (I dunno what its called). Now I realise there is meant to be *some* play there for heat expansion etc... but how much is too much?

Just for clairty: (not my bike) The movement is where the pins are (circled in red)

IF THEY ARE JUST NORMAL RIVETS USED ON DISCS YOU CAN REPRESS THEM BUT BEWARE THERES A TRICK TO IT SO PM IF YOUR GONNA DO IT AND LEARN FROM MY MISTAKE