HarryB Wrote:
I purchased an older used bike that is equipped with Paul Thumbies
shifters, a Shimano RD-M739 rear derailleur and a nine speed cassette.
I can't get the indexing to work properly (have tried clamping the
cable on either side of the screw) and wondering if that is because it
seems that the derailleur is an 8 spd one. It does shift ok across the
complete range of the cassette in friction mode.

If I need to purchase a new derailleur (because I want the indexed
shifting), would one like Shimano's RDM510A (that can be purchased
from Nashbar for $18) be a good choice? I need a long cage derailleur.

TIA,
Harry
Could be that there is too much friction in the cable/housing and/or
too much slop in the RD pivots. I would first try new high quality
cable/housing/metal ends, making sure that everying moves extremely
smooth and easy.
With the cable removed see how the RD moves and how the pivots feel.
Also a check of the chain and cassette for a good 9 speed match and
wear conditions is called for. As chains wear they not only elongate,
they also get less laterally stiff.


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daveornee