loose floating disc

toppy · Nov 2, 2013

My bike has a 13 inch floating type disc and the brake disc its self can move about 1mm on the center hub part. Only up and down you cannot twist the disc relative to the center hub. Is this normal??
The discs like this I have had on modern bikes have always been tight on the center hub. So is this one no good???

Al-otment · Nov 2, 2013

Sounds to be like too much movement. As it's 13" dia. I'm guessing it's from Norvil of which I've heard of other discs from the same source with a similar problem. Historically the only disc to put on a Commando is the pukka 'Norvil' disc as designed by Peter Williams and available from Mick Hemmings. Top quality kit.

Hobot · Nov 2, 2013

Like all good moderns rotor should only be free to shift ~.5 mm in/out from hub and stable in vertical plane.

brxpb · Nov 2, 2013

I have the same disc as you and the disc moves rotationally on the hub, it's as if the buttons/rivets that hold the disc to the carrier are worn ever so slightly, however the disc has only done 1500 miles and was like this from new, perhaps norvil could have used slightly larger rivets but it does not affect the brake in operation in any way. If you hold the front brake and push down on the front it sounds like the forks are clanging but it's the disc knocking the rivets. If you try the same thing with the front wheel against a wall with no brake the front end is silent. (and smooth thanks to Johns' lansdowne dampers).
I have original master cylinder and ap caliper it was a bit on/off but since I gave Hobots penny nail mod a try, I'm more than happy with the brakes.

brxpb · Nov 2, 2013

Forgot to mention that my mate has a WR450 YAM that does exactly the same thing, like that from new, once I saw that I quit worrying about it.

Don Tovey · Nov 3, 2013

I have the 13" Norvil disc with Teeth on the inside that float on an Aluminium carrier.
The Ali carrier is worn & it really rattles badly.
Ive just ordered a new ali carrier & the dish shape bit that goes behind the disc.
It cost about £80 + postage from Norvil. I hope when fitted it will stop the rattling. It does work really well at stopping but sounds very loud when waiting at lights.
A new 13" super light disc cost about £235 + Tax + postage. Its a bloody lot of money. Glad ive got the old ugly style disc on my bike.
EBC used to do a replacement for the superlight style with ref No. 720 but have now discontinued it.
Best of luck sorting it.
Cheers Don

Al-otment · Nov 4, 2013

Don Tovey said:
I have the 13" Norvil disc with Teeth on the inside that float on an Aluminium carrier.
The Ali carrier is worn & it really rattles badly.
Ive just ordered a new ali carrier & the dish shape bit that goes behind the disc.
It cost about £80 + postage from Norvil. I hope when fitted it will stop the rattling. It does work really well at stopping but sounds very loud when waiting at lights.
A new 13" super light disc cost about £235 + Tax + postage. Its a bloody lot of money. Glad ive got the old ugly style disc on my bike.
EBC used to do a replacement for the superlight style with ref No. 720 but have now discontinued it.
Best of luck sorting it.
Cheers Don

Out of interest Don, how many miles before wear between the disc and carrier and rattles? I did have an RGM disc fitted but when that developed rotational movement (after about 35,000 miles) I replaced it with an 11.5" pukka Norvil disc as designed by Peter Williams, from Mick Hemmings. About 5,000 miles so far and all o.k.

Don Tovey · Nov 4, 2013

Hi. I think I've had mine for about 15 years now but not done more than 10,000 miles. I don't know if les emery centres are made by the same people as mick hemmings one or not. The dish shaped bit behind my disc seemed to keep coming loose and maybe this lead to quicker wear and tear. However its quite cheap to replace the worn bits. I would never go back to the standard disc that was fitted when new. Cheers don

Al-otment · Nov 4, 2013

The dish is very important. I assumed the Peter Williams disc (pukka Norvil) was a floating disc until Mick Hemmings pointed out it is semi floating. That is, it only moves as required when centering between the pads under initial braking after installation. The dish is in compression with everything tight and it must have enough 'spring' remaining to keep the disc held firmly after initial braking. The dish definitely shouldn't come loose. Pretty sure this is how it works.

dantriumph · Nov 4, 2013

I had the same problem with my 13" Norvil disc on my Triumph T140. Norvil advised me to fit wavy washers. Their part number is 069578. Never had problems since.
Dan

Nortoniggy · Nov 4, 2013

I have heard of people putting a thin bead of RTV silicon around the bobbins with success.

Ian

brxpb · Nov 4, 2013

Toppy, do you have the gold carrier fixed to the hub with the driiled disc held by the 12 buttons, or do you have the non drilled disc with teeth interlocked on the teeth of the carrier? I'm not sure if we're talking about two different types of disc here.

Don Tovey · Nov 5, 2013

Hi iggy. Your correct. We are talking about two different types of disc. Both seem to have their problems. I think the gold centered one with bobbins\rivvets look a lot nicer than the peter williams ones with internal teeth. Both are a vast improvement on the standard 10 and a bit inch original. I thought the disc on my commando was brilliant after the twin leader on my atlas but how times change. Cheers don

Al-otment · Nov 5, 2013

Nortoniggy said:
I have heard of people putting a thin bead of RTV silicon around the bobbins with success.

Ian

Why would anyone want to take chances with brakes? Floating discs of any design are only supposed to move in the axial direction. Any other movement, even from new, and I definitely wouldn't use. Imagine the consequences of the disc letting go under braking. I'm not too bothered what you do to yourself, I'm thinking about 3rd parties, one of which could be me.

Hobot · Nov 5, 2013

Hehe, this little tinkling noise I held after assembling Peel front wheel gang me pangs of pensiveness I'd screwed up till it dawned on me was just the rotor float slack which checked on to only be axially. I could see if loose otherwise the slam forces could wear pins faster.

toppy · Nov 5, 2013

It says Norvil by Fairspairs on it so I guess its a Les Emery one an that it may be a few years old. its the gold alloy center with 10 pins holding a drilled disc rotor.
the pins have worn by 10 thou but just replacing them will not I think take up the play so a new center is also needed which are available but I was wondering how long before they would be loose or if I did just get the pins an center an reuse the disc which is like new if it would still have play in it.

loose floating disc

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