click-click-click vibration in pedals in all gears after installing new cogs---help?
I have a 1982 Schwinn Voyageur with a 14-28 7-speed freewheel that's been developing a lot of play. It's so wobbly it makes an audible clicking noise as I pedal. So today I installed a new Shimano 7-speed 13-28 freewheel. Now the old clicking noise is gone and it sounds lovely and silent and smooth on the stand, but on the road I can feel a click-click-click sort of vibration in the pedals in all the gear ratios (any chainring, any cog). The closest I can describe it is, it feels the way a single-speed sounds if you over-tension the chain. I feel it only when pedalling, not when coasting, and I haven't changed anything in the crankset, bottom bracket, or pedals. There is no skipping and it shifts just fine.
Here are a few things that we've tried between the LBS mechanics and me:
- measured the chain: using one of those Park Tools gauges that you try to drop into the links, the chain is under .75% wear.
- adjusted tension and limit screws on the rear derailleur
- replaced an inward-facing screw with a shorter one that stops well before hitting any teeth on the smallest cog
- wiped and re-lubricated the chain, jockey wheels, and derailleur pivot points
- removed and re-installed the rear wheel like five times to make sure I wasn't putting it in crooked
- wiggled the freewheel to make sure it was screwed down tight and there was no play in the bearings
- wiggled the rear wheel to make sure there was no play in the hub
The guys at the LBS are scratching their heads too, because usually one of the above will fix it. (Actually, in their experience, one of the first three or four should fix it.) The last hypotheses they haven't tested yet:
- the chain is under insufficient tension because the derailleur is not pulling back strongly enough or the chain is too long, which sounds unlikely because the clicking is equally strong in all gears and also the new cogs are only one tooth off from the old ones.
- This is some kind of weird period of mechanical run-in that will resolve itself after a few hundred miles, which is unlikely because these mechanics have installed these cogs on many other bikes without such problems
Anyone know of any other ideas we could try?