Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 6 Post(s)
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OK, it's a case of divide and consider. Start by pedaling forward and getting the rear wheel up to a decent speed. Stop suddenly and watch the top loop. If it doesn't sag from the wheel pushing chain forward then the freehub is OK, and you need to move on.
If it isn't the freehub, my best guess is friction in the RD pulleys, or simply a sticky chain, from dried lube, or dirt. Shift to high fear and push the cage forward to get some slack, and lift the chain from the pulley and check each for free spinning. If they're sticky, remove them one at a time, field strip, clean and oil them.
Next check the chain by back-pedaling slowly while watching the chain unspool from the lower pulley. Push the cage forward to get a bit of slack in the lower loop. If the chain doesn't straighten immediately as it leaves the pulley, it needs oil, or a bath then oil.
Last, and maybe should have been first, make sure the RD trims well and pedaling forward is smooth and quiet. Poor trim can add friction and bind the chain when you back pedal.
So, you have 10 minute of diagnosis ahead of you. Come back afterward if it's none of the above.
An ounce of diagnosis is worth a pound of cure.
“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin
“One accurate measurement is worth a thousand expert opinions”
- Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance