Indexing on '91 Kona driving me mad...

[Andy R]

Andy R - what aspect of the mech do you suspect may be the cause?

I just meant the things that well-used mechs suffer from - bent/twisted cage, slack in the pivots, too much or too little float in the jockey wheels.

You've checked yours though, and it obviously hasn't had much use, so I think its fair to say that you can eliminate it.

As far as I can tell from the photographs the hanger doesn't seem out of line either and it's not ultra critical.

Have you considered that the detents in a 20 year old pair of thumbshifters may be worn enough to make gear changes inconsistent?
Even when they were new, BITD, one often had to adjust them so that slight overshifting to lower gears was necessary in order to get clean upshifts.

 

[bertberr]

Hadn't given any thought to the shifters, but since you mention it, yes they are old and they do have ultimate control over cable feed to the RD, so perhaps I ought to chuck a new shifter on to see if that sorts it...

 

[Jason802]

Jason802 - that alignment tool looks interesting, can't figure out by looking at it how it actually works...

The alignment tool: screw it in the hangar where the mech screws in, the arm should touch the rim all the way around (or be evenly spaced all the way around). If it's away from the rim in one area, push the tool to bend the hangar in. If it's pushing against the rim pull it out. Simples!

The one I had came with an additional part on the upper arm. This could be adjusted in-and-out to allow for varying wheel dishes etc but as long as you've within say 1/4" of even spacing all the way around you're looking good.

On the cables I'd say just get new ones, or if you're longing for pay day just take the inners out and check they're perfect. Spray some lube down the outers and fit new inners. If you've ever used those inners / outers in a different configuration there's a good chance there's kink hiding inside an outer. Don't forget to inspect the cable guide under the BB, if your cables have sawn through it you'll never get proper shifting.

If you're fitting cables you need a proper cable-cutting tool, it makes shifting much cleaner and sharper just having the outer-cable ends cut properly. THese are overkill but you get the idea: http://www.cyclebasket.com/products.php ... 0s269p1349

I assume you're fitting ferrules on EVERY end of the outers?

Your jockey wheels spin okay but how about lateral play? The top one ought to float slightly side-to-side (like 1 - 1.5mm), but it should remain upright and not flop much at all. The bottom one ought to have virtually no lateral play, they're not the same and must be placed and assembled correctly.

Your mech ought to get some attention. Move the bottom of the cage with your hand and see how it feels. It's not unusual to see 1" of play on the bottom of a long-cage mech but that doesn't matter too much. Being newish it should be fine.

If all that don't work maybe the cassette has been assembled with the spacers in wrong. I can't remember how many were loose on those or if they even CAN be mixed up (due to their keyway fittings), can you take a pic of the cassette sighting down the cogs? You should see that they're pretty evenly spaced.

That's all I can think of for now other than - take it to your local bike shop!