here are a couple of numbers:
- numbers of cogs, or gears in the cassette, these days you will find bikes with 8 or 9 or 10
- 11-21 or 11-23 or 12-etc., etc., is the number o4 teeth of the smallest and the biggest cog. So a 11-23 cassette will have a smallest cog of 11 teeth, and the biggest cog of 23
- another number that is important is the "difference", which is the "biggest - the smallest" ex. on an 11-23 cassette the difference will be 23-11= 12
there are some other numbers which involve the front crank set chain rings..
here is a short description of the the other numbers and why they are important (from the Campagnolo website Q&As)
I would like to see some examples of compatibility calculations for sprocket sets, dérailleurs and crank sets
Let's take a look at a practical example:
Can the Centaur 10s rear derailleur be used with the 13-29 sprocket set and the 39-53 crank set?
The description of the Centaur 10s rear derailleur reads: minimum sprocket 11, maximum sprocket 29, capacity 30 and maximum front difference 14.
The minimum sprocket and the maximum sprocket are therefore perfectly compatible.
Capacity = (29-13) + (53-39) = 30
Front difference = (53-39) = 14
The Centaur 10s rear derailleur can therefore be used with the 13-29 sprocket set and the 39-53 crank set.
Second practical example:
Can the Centaur 9s rear derailleur be used with the 13-23 sprocket set and the triple 30-40-50 crank set?
The description of the Centaur 9s rear derailleur reads: minimum sprocket 11, maximum sprocket 29, capacity 30 and maximum front difference 14.
The minimum sprocket and the maximum sprocket are therefore compatible.
Capacity = (23-13) + (50-30) = 30
Front difference = (50 –30) = 20
The Centaur 9s rear derailleur cannot therefore accept the maximum front difference of the triple crank set; the Centaur triple 9s rear derailleur should be used, with a maximum front difference of 22 teeth.