Can we make a sticky about Shimano / SRAM / Campagnolo gear spacing and interchangeability? I would like it to include the following information:
For Road Bikes:
9 speed__________3.3 / 3.0*____2.6______4.0
To use these tables: For the rear derailleur you propose to use, divide the gear spacing by cable pull to obtain actuation ratio:
Campy New 1.5, Campy old 1.4, Shimano 1.7, SRAM 1.1
If using Jtek shiftmate, multiply or divide by shiftmate ratio
Type 1=1.04, 2=1.07, 3=1.2, 4=1.13
Multiply the final actuation ratio by the cable pull of proposed shifter to obtain new derailleur mechanism actuation.
If this is within 0.5mm of an available cassette it will shift very well. If it is within 0.1mm of an available casette, it will shift OK. Greater errors make worse shifting, you can always try it to see if it's tolerable.
Use a 9 speed chain for anything 9 speed or less. Use a 10 speed chain for 10 speed. Campy 11 is Campy 11, don't use it unless you need it.
Match the derailleur pulleys to the chain used - conversion pulleys are easily available. If going large to small, a washer under the head of the pulley bolt will stop the end of the pulley bolt protruding too far in. If going small to large check that enough threads engage on the pulley boilts.
Say I have old Campagnolo (1st generation 9 speed) shifters and I need to replace the derailleur with something available from the LBS which carries Shimano and SRAM.
If I choose SRAM 10 speed, with an actuation ratio of 1.1 and use a Jtek type 1 I get a derailleur action of 3.3 x 1.1 x 1.07 which is 3.88 mm. The nearest suitable spacing for Shimano / SRAM is 3.95 mm (10 speed), the error or 0.7 mm per shift will result in acceptable shifting.
If I use a Jtek type 4 I get 3.3 x 1.1 x 1.13 which is 4.10 mm, the nearest suitable spacing for Campagnolo is 4.15 (again 10 speed). The 0.5 mm error should result in good shifting.
In both cases I will only be able to use 9 of the 10 speeds because the number is set by the indents in the shifter mechanism.