I commute on an old (1989ish) Bianchi Tangent cyclocross bike with Suntour XC Comp components. I love it, but that's not the point of the thread. Recently one of the sprockets on the rear wore out and I had to replace it. Turns out, the Suntour cassettes have different splines than anything that's currently made and a new old stock cassette is at least $80 on ebay! I also can't change to a Shimano hub/cassette without giving up index shifting, since the sprocket spacing is different.
My question is: how can I keep the bike rolling with mimimal hassle and expense? My thought so far:
1x Shimano 7-speed hub
7x 2mm (5 or 6 speed) Shimano sprockets in appropriate sizes
3x 2.8 mm spacers (I think campy 9-speed uses this size so it should be available)
3x 3.0 mm spacers (Shimano/SRAM 8-speed uses this size)
The math adds up OK, that is if the Campy spacers fit well on the Shimano FH body.
It does not appear that 6 speed Shimano cassettes are very inexpensive, either.
Maybe just best to keep your eyes open for good deals on the Suntour parts.
With a little digging, I think I've found a better solution. I'll get an 8-speed cassette and add 0.5mm spacers to the last two gears. Sources vary, but apparently the higher (physically smaller) gears have 3.3mm spacers, making the total center-to-center width 5.3mm between the three smallest sprockets.