[Note: this is just one way to get a pre-2001 9-speed Campagnolo shifting system to work with a 9-speed Shimano cassette. There are other—perhaps better—solutions now including using a JTek Shiftmate or using a post-2001 9-speed Campy shifter cog (in the Ergopower lever) in conjuction with a pre-2001 Campy rear derailleur.
In ’99, I made the switch to a Campagnolo shifting system (Ergopower levers, crank, derailleurs, etc.), but wanted to retain my wheels with Shimano hubs. There were two reasons for this: (1) wheels are somewhat expensive ($200 for my set of Mavic CXP33 rims and Ultegra hubs), and (2) Campagnolo cassette freehubs are LOUD! This is one area where it is my opinion that Shimano has the edge: while coasting, my Ultegra hubs are virtually inaudible.
Fortunately, the spacing between a Shimano and Campagnolo 9-speed cassettes are similar enough that they can be adapted. In fact, according to some USENET newsgroup cycling enthusiasts, a Shimano 9-speed cassette can be used as is with Campagnolo components without any modifications whatsoever, as long as the narrower Shimano chain is used. However, perhaps because I was using a Sachs chain, shifting did not seem to be perfect, so I decided to modify the spacing of the Shimano cassette to make it more similar to Campagnolo’s.
The spacing between the largest 5 cogs in both Shimano and Campagnolo cassettes is 2.5mm. However, the spacing between the smallest 4 cogs in Shimano’s is 2.5mm, whereas it is 2.8mm in Campagnolo’s. Hence, the trick is to increase the 2.5mm spacing between the smallest 4 Shimano cogs to 2.8mm.
I easily achieved this by cutting shims out of an aluminum can. Two shims add the required .3mm! Since there are 3 gaps between the 4 cogs that need to be 2.8mm, however, 6 of these shims are needed. I actually only used 5–just 1 between the smallest 2 cogs–and can report near-flawless shifting. Using 6 shims makes it difficult to install the cassette lockring. I also discarded the “built-in” shim/washer on the Shimano lockring.
See below for a step-by-step pictorial.