front disc loose!

[torbs]

Servicing front brakes-calliper n/s jammed upper slider- heat loosens- sorted. Now checking discs and inner disc is loose on bolted outer?!! any cure!-looks like the 2 are held by a kind of rivet. Its the standard disc as on 98 model (WEMOTO pic is same) heeelp! £120 new one!

[amorti]

Hi Torbs,

first off, take it easy - it could be normal! The outer disc is made of steel for durability, the inner disc is made of aluminium for lightness. Because these materials expand at different rates with heat, they must be joined loosely by rivets, otherwise they would buckle as surely as a bi-metallic strip bends. So there is meant to be play "in-and-out" on the disc. A minimal amount of rotational or back-and-forth play is permissible, like for example on early Fi Triumphs (I had a T595), but this should be minimal.

If you (or more importantly your MoT man) feel that the play is too much, then you may need to replace the disc. It might be possible to drill the rivets out, but I have no clue where you would get replacements. It is usually that the rivets wear or squish, but could also be that the aluminium carrier has worn or the holes gone oval.

The other idea that occurs is that if your other disc doesn't move, then that is the one which is "wrong". Try spraying brake cleaner into the non-moving disc's rivets and working it in, as sometimes brake dust, rust or ally corrosion will cause the rivets to jam. If that happens, you are looking at a pringle-shaped disc in the near future due to that bi-metallic strip effect.

[General Gman]

Good method to free off the buttons is to remove the disc, support it firmly and then , using a block of wood, give each one a series of sharp taps .Usually frees them up IME
You can also use a nut and bolt secured through the button and tightened up to rotate it , using brake cleaner to help out.
As the man said, a small amount of play is normal

[m40man]

Apr 6, 2011 9:26:54 GMT amorti said:

.... Because these materials expand at different rates with heat, they must be joined loosely by rivets, otherwise they would buckle as surely as a bi-metallic strip bends. So there is meant to be play "in-and-out" on the disc....

I concur with the young Softy Southerner whippersnapper . When a bit worn, they can create quite a rattle some time before replacement becomes necessary.

[torbs]

cheers mdears! Will whip disc off as currently servicing calipers and get my local man to check it-MOT for SR500 tomorrow would seem good timing!