Sti shifter issues
 

I have a set of shimano rsx 3x7 and I'm having trouble with the rear shifting.
When I click up from the smallest to the larger cogs it shifts perfectly until about the middle cog but from there on the derailleur doesn't move enough to shift the chain to
The next cog. Im using the correct type of housing so I don't think housing compression is the issue. Could it be that the cable is stretching as the tension increases? I'm having this problem on both of my sti equipped bikes. The other is a 2x7 sora.
I know they aren't the best groups but I do expect them to at the very least function as they should. Help and advice would be greatly appreciated.

Have either of them ever worked on your current set-ups? I ask because the limit screws may be adjusted for another dropout and they may be preventing the shifter from moving the parallelogram sufficiently in order to move the chain to your larger rear cogs.

If they have worked previously (and in any case), check:

- the cable hasn't stretched
- the cable hasn't slipped in the pinch bolt on the derailleur
- hanger alignment
- that cables are sufficiently lubed / no gunk in the housing.

HTH :)

I would start with hanger alignment.

Hanger alignment seems ok on both bikes. The issue appears to be cable tension related because the higher the tension, the less the derailleur moves. I'm ashamed to admit I'm using walmart shifter cables which are probably a little stretchier than quality ones. They'd work fine for friction but not so much for index. I'm putting in a nashbar order tonight. I'll pic up a couple sets.