Does this just require a 5mm spacer? I've read that you can do it quite happily but I have no idea where the spacer would go or where to get one.

2.5mm spacer from HT2 type BB(try your LBS)fitted between drive side cup and BB shell, nowt usually needed on the other side.

I think I've got one knocking about. Cheers Coatsy.

do you mean you want to use a 68mm bb on a 73 mm shell ? If yes surely you won't need any spacers involved , if No what are you trying to do.(probably obvious and i'm confused 😀

Which BB? The Raceface Signature can do both, either wined in one rotation for 73 or out one rotation for 68 form flush with the shell.

be nice if you replied having asked a question

Be nice if I read the original question properly too, read the post and assumed he had a 73mm BB going in a 68mm shell, i'm confused too now.

The RF Signature still needs to be used with the spacers provided with it Spence. You can't just leave a heap of thread showing.

Neither of the two Sig XC's I've had came with spacers. The fitting instructions only say a 2.5mm spacer is provided with the DH models (different flanged cups) and then only describes using it to adjust chain line.

When using with a 68mm shell there is only 1mm of exposed thread (with the XC gold cups) hardly a heap and not enough to thread a spacer on. Why? Never had a problem.

Good BB by the way.