Worn floating disk buttons

[-Ralph-]

I MOT the bike in March and I got an advisory for rotational play from the button drive rivets on my front discs. Since then Ive started to get uneven braking coming to a stop from 20mph or so downwards. Dont feel anhghing through the lever, just the braking force is on/off/on/off and the bike comes to a stop like a nodding dog.

It feels like a warped disc but I dont see how that would show itself on a floating setup as it should just compensate for it.

I can understand button rivets jammed up with brake dust etc causing that problem, but not loose rivets.

Any ideas??

[Bibio]

Colin stop being a tightass and get a new discs mate. do you really want to be going down the road then go for your brakes in anger for them to suddenly come off the buttons?

[andrewsmith]

Colin stop being a tightass and get a new discs mate. do you really want to be going down the road then go for your brakes in anger for them to suddenly come off the buttons?

This
If they dont seem right replace them

[-Ralph-]

MOT guy said no danger from the disks, showed me a few other bikes in his shop that were the same and said it'd probably go through another couple of MOTs like that at my annual mileage before the play failed the MOT and they had to be replaced. Triumph replacement discs are 5-600 quid, and an aftermarket replacement like EBC are 300. If its a problem I can sort with compressed air and a scoosh of brake cleaner, do I really want to replace the discs??

[Bibio]

how much is your life worth to your family?

i can understand what the MOT inspector is saying but i always take an advisory as 'i can't fail it but i'm recommending you fix it'.

might be worth phoning someone like blackshadow to see if they can replace the buttons if the discs are ok.

[-Ralph-]

Is discs coming off the buttons under braking something that anyone has heard of happening before?

Dont get me wrong, if the discs need replaced I'll replace them. It's not like I cant afford 300 quid, but Im not convinced that the problem is the discs, hence this thread. If they were warped wouldnt I feel it through the lever? Also the bike has only covered 6000 miles. Discs knackered after that mileage?

That said Specialones Sprint ST is in now getting new discs under warranty after 10000 miles, but exactly what us wrong with them Im not sure.

[mostin]

Had the same problem with my front brake , the nodding dog effect. Found play in the disc buttons on both front discs , one was worse than the other. You could move the outer part of the disc slightly, [rotate it - not sideways movement]. I concluded that it could not be right so I looked around on the net for replacement discs - saw some cheap ones and found some poor reports , took the plunge and bought ebc s. Braking problems sorted ! No movement in new discs.

[svrich]

I had this on one of my front discs. The spring/washer on most of the bobbins had shrunk back from the disc, or had rusted through. I was sure that something wasn't good but nothing moved by hand (no more than natural play) but I guess the rust was holding it together enough until that went and the big 'play' became easy to notice. I swapped out the discs as a pair and all was instantly well again. I'm sure that you could get the bobbins replaced rather than the complete disc set-up, so long as they aren't damaged.

[suzukigt380paul]

if in doubt change them,but ive never heard of disc's coming off the buttons no matter how loose they are,as long as they are just loose and nothing is damaged,ive used disc's on my old gsx600f with about 4mm play on the buttons with out any problems,but they do tend to rattle on rough roads

[yorkie_chris]

Is discs coming off the buttons under braking something that anyone has heard of happening before?

Only once with a galfer, the disc actually snapped.

[garynortheast]

Just wondering if it's possible to get the bits to do something like this - http://www.bmwmoa.org/forum/showthread.php?t=573

[AndyBrad]

I've got a brand new set of triumph oem disks here that ill swap for a new roulette green speed four belly pan :)

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[Sid Squid]

Try wiggling the disc when it's properly, properly hot - not with your hand obviously.

Some discs are quite loose when cold and tighten up when hot, some do it the other way round.

[Lozzo]

Is discs coming off the buttons under braking something that anyone has heard of happening before?


I didn't lose the discs, but I had two buttons ping off the fully floating AP Racing narrow track cast iron discs that were fitted to my GSXR1000, one from each side. The discs were exhibiting the same symptoms yours are, juddering when coming to a stop and generally quite clanky when moving the bike about. Replacement bobbins were available, but rather than muck about trying to repair a problem I knew would reoccur I swapped the discs for a set of PFM ductile iron ones that were much better made.

[yorkie_chris]

On some clanky ones I've got it appears to be the carrier which is distorted rather than the buttons worn.

[-Ralph-]

No clanky problems, they are not that loose (maybe 0.5 - 1mm of play at most). Under very hard braking they will give a vibration, but the problem is not what I'd describe as judder, it's a slow 'nodding dog' surging on and off effect which makes it impossible to get the bike from 15mph down to a stop, smoothly, under the front brake, have to switch to using the back brake only. You only feel it below about 15mph.

If it were a solid disc on my XT600, I'd say the disk were warped if I had that kind of sensation under braking, but on floating discs with less than 6000 miles of use, there wasn't a problem when I bought the bike (3600 miles), and I'm not a rider that hammers on the brakes then tips into a corner, or leaves braking for junctions to the last minute, I just find it hard to believe the disc is warped. I doubt I ever even get them that hot.

[Bibio]

i completely burgerd a brand new gsxr 1000 k1 disc on the last bike within 100 miles because of a dragging front calliper.

give it a go with brake cleaner and compressed air to see if there is any crud in the rivets but if it doesn't rectify it then new discs time. but the nodding dog sounds like there is a warp. get the front up on a stand and spin the front wheel to see if there are any high spots on the discs.

don't **** around with brakes Colin as you might just regret it.

[AndyBrad]

I had the same using nissin pads. Too grippy. Also triumph disks are k.own for it.

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[Richie]

My Aprilia disc (tuono forks and discs) are loose when cold too :0) haven't tried wiggling them when they're hot... Will do next time.
Cheers for this Thread Ralph, and cheers Mr Squid for the info :0)

[sno335]

Hi new to the forum but just some info about replacement disc buttons.Mine were badly corroded on my 2004 650.I sourced my nice aircraft aluminium ones from a company in Germany.www.performance parts.de
About €30 per disc(6) 4.5mm thickness
You need to carefully grind off the turned over bit of the old river.The new ones push in and secure with a C clip.
Apologies if this is common knowledge

[sno335]

Just to clarify, the buttons are 16mm x 4.5 mm thick
Various colours available

[Dave20046]

Hi new to the forum but just some info about replacement disc buttons.Mine were badly corroded on my 2004 650.I sourced my nice aircraft aluminium ones from a company in Germany.www.performance parts.de
About €30 per disc(6) 4.5mm thickness
You need to carefully grind off the turned over bit of the old river.The new ones push in and secure with a C clip.
Apologies if this is common knowledge

Useful. thanks

[Bibio]

DONT use those replaceable buttons. if it were not for me doing about 3mph in a car park i would be dead... one of those buttons failed on me a few years ago, when it spat itself out it bent the rotor and brought me to a full stop. if it had happened 2min later i would not be here to write this warning.


BUY NEW DISCS.......... and before you say i fitted them wrong... i do know one end of a spanner from another.