Originally Posted by
ColonelJLloyd
I guess I phrased the question both ways in my post. Please clarify; will the Altus derailleur have enough travel?
It will. I am currently using a very old Shimano Acera rear derailleur meant for 5 speeds with a 9-speed cassette, 9-speed chain, and indexed shifters.
Bike companies will often tell you need new stuff, either because they never try the old-new combo and can't guarantee it will work, or because they want you to buy more stuff.
With every single shimano derailleur I've tried from the early 80's on, the travel is plenty. The only issues with derailleurs usually involve using indexed systems. If you use friction shifters, by the way, you could probably even run a 10-speed chain and cassette with your current set up. EDIT: But I would stick with the 8.