Wiggly disc brakes?

[Trigress]

The disk is firmly attached to the hub, and there is no visible damage to the flange or hub.[...] Trust me on this. When I say there isn't a wiggle, there isn't one. When I say there is, there may be - or it may all be in my head. (Trigress sometimes employs pop-psychological jargon about this...)

Well, it turns out that this might be applied the other way too - when there isn't a wiggle, there might not be a wiggle, or the lack of wiggle may be only in your head. There is an infinitesimal chance of your hearing this again, dear.

After a fair amount of dismantling, wiggling of various bits and bobs and tightening of various bits and bobs, it finally turned out that the disc was in fact a little wiggly. It should be mentioned that this wiggle was undetectable by wiggling the disc, wheel unmounted and using only bare hands, we could only feel it and see it when applying the brakes and then wiggle the wheel. Anyway, we tried to tighten them to the wheel, but the wiggling persisted. There seems to be a slight wiggling room between the locking teeth on the wheel and the locking teeth on the disc.

[Triger]

It should be mentioned that this wiggle was undetectable by wiggling the disc, wheel unmounted and using only bare hands [...]

...It really should! I feel half excused

[DebW]

The larger question is, is it the disk or the hub? Hopefully it's the disk. I'd definitely try to fix it soon, because even if it's the disk, it could be wearing the hub and eventually require you to replace both hub and disk.

[ridebikeme]

By your description, I wonder if they are Shimano brakes? If so, you should be sure to check that the connection where the disc mates with the hub doesn't some sort of wear problem. If it's a Shimano system, then the disc locks onto the hub similar to a cassette locking onto the freehub. If any wear is present there, then you'll need to address that. I have seen a number of these systems, and it definitely was a design flaw from Shimano. You should have your LBS take a look at it before it becomes a bigger issue.

[Trigress]

It is indeed a Shimano system, and your description is quite accurate, it's just that I didn't know the words (it is most definitely a handicap not knowing these parts names in English...)!

Will it be enough just to buy a new disc or is there something else I need to have sorted out?

[ridebikeme]

No, buying a new disc will not help. The problem seems to be that the connection with how the disc and the hub mate is loose... it's very similar to having a loose hub. I would definitely have your LBS take a look at it, you could develop wear in that area and cause all sorts of other problems. If you are trying to take care of it yourself... then you'll need to pull it all apart and tighten everything. Let me know how it goes!

[Trigress]

I have already taken it to bits and tightened everything, with no effect whatsoever... There is simply too much air in between the disc and the hub, and I can't really see how that can be mended - unless I get a hub and a disc that fits snugly. I'll see my local bike repairman about it and let you know what happens!