How easy is it to swap sprockets?

[onlyhuman]

8 speed Campagnolo Athena, 1990s. I currently have a 13-23 cassette, it doesn't seem badly worn and I would like to extend the range a bit. Can I replace the larger sprockets individually with still larger ones? How easy will it be to get the sprockets, is it a difficult job changing them, will it be economical or should I just buy a new cassette? What about the gap in size between two sprockets, are there rules for how many teeth of difference there can be?

 

[MartinC]

8 speed Campag cassettes are still available (e.g. about £30 from Ribble). You can get a 13-26. Sourcing individual sprockets would be really hard - maybe you might get a Marchisio one but it wouldn't be cheap. 8 speed freewheels were steel and had shallower splines than 9 speed so 9 speed sprockets won't fit. Just moving sprockets around on the cassette doesn't always work well - sprockets are 'timed' so that the pick up teeth on the cassette line up properly in relation to the sprockets either side. You ideally need a sprocket of the right type (not just number of teeth) for the position on the cassette.

 

[TheDoctor]

My LBS has 8 speed campag cassettes. 13-26 or 12-23.
Hope this helps.

 

[onlyhuman]

Thanks Martin and The Doctor, it looks like new cassette is the way forward.