Thanks for your input, I think you are describing another option which I also thought of over night. I can get a 9 speed HG cassette and then canibalise the parts as follows to fit on my existing DA uniglide hub. I will check tonight whether my hub also has the HG internal threads for a lockring but I'm 95% sure it doesn't. However my hub looks very much like this one
http://www.velobase.com/ViewComponent.aspx?ID=0FF361BC-8EEF-4845-AC11-5AC2756C95D4&Enum=110&AbsPos=213 which according to the blurb does have HG compatibility; The first model sounds exactly like what I have "FH-7400 6/7 speed UniGlide (reduced diameter 31.8mm UG thread to allow 12T sprocket)". However my hub is 126mm not 130mm, but 6/7 speed is always 126mm? I am at work so will check when I get home, if I do have HG compatibility then its great news indeed since I can simply get a 9 speed HG cassette and use 8 cogs from 9.
Photo from velobase:
Here's a picture of my exact hubs before I had then made up into wheels; pretty similar to the above eh?
Assuming I have to stick with the UG option, then my idea is similar if not the same to what you described:
- New HG Cassette would ideally be something like 12-32 so the second largest cog is 28T (biggest my RD will take and which is what I need). Ideally a cassette with sprockets 12-13-14-16-18-21-24-28-32 but this is difficult to find. May be other options will work like 11-28 since I am not using the 2 smallest cogs, need to look into this further.
- Current cassette is I think 12-27, the 12T and probably adjacent 13T sprockets are specific to this UG hub and so need to remain. This puts the spacing of the two smallest cogs a little wide as 7 speed spacing is 5mm, 9 speed spacing is only 4.34mm. I may therefore have difficulty shifting to the 13T and probably won't shift at all to the 12T but perhaps I can frig this (I will be using 9 speed brifters with 8 cogs so the additional "not used" position could be the low position and move the RD more than 1 cog to its stop to allow the 12T cog to engage). If these cogs are not available it doesn't matter since I hardly use them.
- I the take some of the spockets from the new HG cassette together with the slimmer spacers and mix with the 2 smallest sprockets on my UG cassette as follows:
- 12,13, use original UG sprockets
- 14,16,18,21,24,28 sprockets from new HG cassette with the thinner 9 speed spacers
- 32 sprocket gets chucked, so I'm using "8 from 9" configuration
I then believe I need to use Shimano brifters with shimano RD since Campy has different lever/cable ratios and cable/movement ratios on the RD? I don't quite understand your last bit about using Campy brifters, I'm don't understand how this can work is the various ratios are different?