Originally Posted by
Ronno6
Sorry. I have responded to both threads. The LBS installed a RD-4500, which is a short cage.
Must have been what they had on hand.
However, typically it should not have mattered. 6s,7s,8s,9s,10s; I have used them interchangeably without incident (except 7400 DA.)
In this case I have read that Shimano added the 30t cog when they went to 10 speed
in that group. Apparently, that's where the problem arises.
Here is what I have read about using a 9 speed deraileur with a 10 speed cassette on another forum
"
The spacing between 9 speed and 10 speed is controlled at the shift lever.A 10 speed rear dérailleur will work with a 9 or 10 speed cassette and shifter. A 9 speed rear dérailleur is not compatible with 10 speed.
The width of the chain and the cogs is the biggest issue. The pulleys on a 10 speed dérailleur are narrower, and a 10 speed chain will not rest correctly on the jockey pulleys of a 9 speed dérailleur.
That does not mean it will not physically work, only that the shifting performance will be slow, you may drop gears unexpectedly, or have the chain skip unexpectedly.
Long story short, 10 speed should be 10 speed all the way throughout your bike for it to work consistently and properly.
Cable tension has nothing to do with cog spacing. That is designed into the shift lever. It is not adjustable, except by replacing the shifter. I hope that helps."
Which is why I want the original set up back because for me the gearing is messed up and I paid for a direct replacement, not an older or different model.