sinican

Hi,

I have a bike that's equipped with a shimano 600 rear derailleur and 8-speed (shimano) cassette. The original 600 shifters are banged up and I installed a pair of new shimano 8-speed bar-end shifters. As I go through the motion of threading the cables through the housing and setting the indexing on the derailleur. I encounter a problem:

The derailleur can down-shift (toward larger sprocket) fairly correctly, but when it shifts back up to smaller sprockets, the chain will shift, but will rub against the next larger sprocket. I have fiddle with it to no end, and still can't get it to work exactly.

I have a few theories, and hope people can give me comment and telling me which (if any) of my theory is a probable cause.

1. The rear derailleur has been heavily used, and is a little banged up. The spring tension of the derailleur might not be as high as when it was new, and can't coil back as much when I up-shift (and thus reduce shifter cable tension). This causes the chain to shift to the next smaller sprocket, but not completely and rubs against the larger sprocket. If this is the case, I will change to a new derailleur.
2. I did not replace the derailleur cable and housing when I installed the new shifters, because they look to be in decent shape. Maybe there is friction inside the housing to delay release of cable as I up-shift. If this is the case, i will change the cable and housing for the rear derailleur

A side question, can I use a shimano deore rear derailleur that is long cage to replace this shimano (i have a double crankset in the front)?

Please give me advice