deliquium wrote:Or would a custom 9 speed 12-13-15-17-19-21-24-28-32....?
sounds OK but for 9s I think an easy route ahead is to use parts from a 13-25 cassette,
13-14-15-16-17-19-21-23-25
but delete the even numbered sprockets and add a 28 and a 32T giving
13-15-17-19-21-23-25-28-32
however it may get complicated because
a) the top two sprockets are often a nested pair (with a counterbore in the 12T one for part of the 11T one, for example) and/or
b) the top sprocket uses a matched lockring. If you delete the top sprocket then you may need a different lockring and/or the lockring won't bear against a serrated face. In the latter case you might want to use some threadlock on the lockring thread.
Useful info about HG50 9s cassettes here
http://bike.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/CS/EV-CS-HG50-9-1880C_v1_m56577569830799948.pdfratios;
- 11-25T - 11 / 12 / 13 / 15 / 17 / 19 / 21 / 23 / 25
- 11-30T - 11 / 12 / 14 / 16 / 18 / 20 / 23 / 26 / 30
- 11-32T - 11 / 12 / 14 / 16 / 18 / 21 / 24 / 28 / 32
- 11-34T - 11 / 13 / 15 / 17 / 20 / 23 / 26 / 30 / 34
- 12-23T - 12 / 13 / 14 / 15 / 16 / 17 / 19 / 21 / 23
- 12-25T - 12 / 13 / 14 / 15 / 17 / 19 / 21 / 23 / 25
- 12-27T - 12 / 13 / 14 / 15 / 17 / 19 / 21 / 24 / 27
- 13-25T - 13 / 14 / 15 / 16 / 17 / 19 / 21 / 23 / 25
- 14-25T - 14 / 15 / 16 / 17 / 18 / 19 / 21 / 23 / 25
and 8s ones here
http://cycle.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/CS/EV-CS-HG50-8-3072A_v1_m56577569830818508.pdfratios;
11-13-15-17-19-21-24-28T
11-13-15-17-20-23-26-30T
11-13-15-18-21-24-28-32T
12-13-14-15-16-17-19-21T
12-13-14-15-17-19-21-23T
12-13-15-17-19-21-23-25T
13-14-15-16-17-19-21-23T
13-14-15-17-19-21-23-26T
IIRC it is OK to use several flat 8s sprockets (with 9s spacers) within a 9s cassette.
cheers