Rattling discs.

[TomL]

When we were spinning up Ron's front wheel the other day to check the wheel bearings, we found that the discs were so loose that the rattle of them floating about almost drowned the noise of the knackered wheel bearings. The right disc is much looser than the left disc.

How loose is acceptable?

[raesewell]

If it goes rolling down the road in front of you Tom I'd say that was unacceptable 

[Costas]

They should allow a play of about 0,3mm each time you you move them at any direction .

[drumwrecker]

If the disc is OK and the bobbins are worn but they come fixed with the disc what then?
I see some models you can buy the top hat type bobbins.

[Costas]

Right side disc is corectly worn faster that the left one due to brakes circuitry design , but this is something noticed after 80000 kms. Unless the pads are to hard on discs, Carbon Loraine comes to mind.

[drumwrecker]

Do you mean CL pads might be too hard on discs Costas?
I thought you recommended them for the K13s?

[Phmode]

I'm not sure that loose discs (on the bobbins) is a problem; the action of the pads makes them run true during braking.

It would be much more of a problem if there was no play, or float, as that would mean 'fixed' discs and no gurantee that they were 'fixed' in the correct 'plane'!

The only downside I can see to discs with a lot of 'float' is if there is too much free movement at the lever under initial braking as this might mean that the 'rattling' pads were knocking the discs and therefore the pistons, back.

This would not be a 'good thing' 🤕

[TomL]

I'm not sure that loose discs (on the bobbins) is a problem; the action of the pads makes them run true during braking.

It would be much more of a problem if there was no play, or float, as that would mean 'fixed' discs and no gurantee that they were 'fixed' in the correct 'plane'!

The only downside I can see to discs with a lot of 'float' is if there is too much free movement at the lever under initial braking as this might mean that the 'rattling' pads were knocking the discs and therefore the pistons, back.

This would not be a 'good thing' 🤕

It's not so much the pads but the discs floating about on the bobbins.

[carl0s]

I replaced mine with the brembo ones from an italian website. They were about 100 euros each I think and came with replacement bobbins and springs. Tight as anything now. They can still move side to side on the springs, very slightly, but they no longer rotate forward/backward and click like they did when I got the bike. I was eliminating sources of noise and this was one that I wanted to check off the list.

here's my order details from carpimoto.com :

Content of the Order
Item Description   Qty.   Availability   Price
168B407D7 - Brembo Serie Oro Brake Disc 168B407D7, one (1) disk, for BMW, dim 320x181 mm; holes distance 203mm, holes diameter 14mm, thickness 5mm   2   In Stock   €  203,26
07BB26SA - Brake Pads Brembo 07BB26SA sintered street (1 couple for 1 disk), BMW > 2001   2   In Stock   €  58,38
Items Total VAT / Tax included   €  261,64
International Standard 3 business days   €  0,00
Credit Card   free
Total  VAT / Tax included   €  261,64

[Phmode]

I'm not sure that loose discs (on the bobbins) is a problem; the action of the pads makes them run true during braking.

It would be much more of a problem if there was no play, or float, as that would mean 'fixed' discs and no gurantee that they were 'fixed' in the correct 'plane'!

The only downside I can see to discs with a lot of 'float' is if there is too much free movement at the lever under initial braking as this might mean that the 'rattling' pads were knocking the discs and therefore the pistons, back.

This would not be a 'good thing' 🤕

It's not so much the pads but the discs floating about on the bobbins.

And that was what I was addressing as you see from my first line 

[Phmode]

I replaced mine with the brembo ones from an italian website. They were about 100 euros each I think and came with replacement bobbins and springs. Tight as anything now. They can still move side to side on the springs, very slightly, but they no longer rotate forward/backward and click like they did when I got the bike. I was eliminating sources of noise and this was one that I wanted to check off the list.

here's my order details from carpimoto.com :

Content of the Order
Item Description   Qty.   Availability   Price
168B407D7 - Brembo Serie Oro Brake Disc 168B407D7, one (1) disk, for BMW, dim 320x181 mm; holes distance 203mm, holes diameter 14mm, thickness 5mm   2   In Stock   €  203,26
07BB26SA - Brake Pads Brembo 07BB26SA sintered street (1 couple for 1 disk), BMW > 2001   2   In Stock   €  58,38
Items Total VAT / Tax included   €  261,64
International Standard 3 business days   €  0,00
Credit Card   free
Total  VAT / Tax included   €  261,64

Nice find, thanks for posting it up