conflicting reports on 10 speed derailleur - set me straight.
I just ordered a 9 speed shimano compatible brake lever shifter set and the 10 speed Shimanho 105 rear derailleur thinking I could adjust the derailleur to fit pretty much any gearing as long as the shifter and gears match. But I have been reading that one cannot use the 10 speed derailleurs with the normal 7/8/9 speed shifters and cassettes. I have read opinions BOTH ways, that one CAN and one CANNOT. Which is it? Please remove this confusion from my brain....
anything marked dynasys must be used with dyna sys parts. your plan should work fine
All non dynasys (Which is a mountain bike thing) SIS RDs should be compatible, at least as far as travel goes. I have had bad luck using some pre-SIS8 RDs, but that could be due to other factors.
A 105 RD should work fine with 9 speed shifters, and many bikes were sold with 9 speed Tiagra and 105 RDs.
It is possible there some some variation in cage width, since 10 speed chains are narrower, but it shouldn't cause issues with 9 and 10 speed components. 8 and 10 maybe, but I'm not sure.
Ride, Wrench, Swap, Race
The 10s 105 derailer will work fine with 9s chain and shifters.