Originally Posted by
JeffOYB
Apparently it's more about the chain than the cassette. Coz my 10sp shifter w a 10sp chain worked fine with 6, 7, 8, 9 sp wheels...
Has nothing to do with the chain.
If you have 10 speed index shifters it will not work with 6, 7, 8 speed. Alternate cable routing for 9 speed cassette.
The reason it is impossible is because of cassette cog spacing (Shimano).
6 speed is 5.5mm
7 speed is 5.0mm
8 speed is 4.8mm
9 speed is 4.34mm
10 speed is 3.95mm
When you use a 6 speed cassette and then a 9 speed cassette, how does the same index shifter adjust the amount of cable to pull to move the correct amount.
Now if the shifters are friction, you can run anything you want. But there are technically no “speed” friction shifters.
John