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: 28 Post(s)
Tagged: 1 Thread(s)
Quoted: 1150 Post(s)
I strongly doubt that it's a pulley related problem. Any friction in the pulleys would only serve to keep the chain in the lower loop, the exact oposite situation to yours.
Usually when the chains spools into the upper loop, and slops onto the chainstay when coasting, it's a freehub problem. There's excess internal friction, and the freehub isn't truly free so the spinning wheel pushes it forward. Often it also shows up as the pedals turning when you walk the bike.
I'd recheck the freehub for sources of drag, and also consider the choice of lube used. An overly viscous lube (except in the ball bearings area) creates excess viscous drag, or in the case of a spinning wheel, viscous propulsion similar to what happens in the torque converter of an automatic auto transmission.
BTW- if it was recently serviced, and the same folks still can't solve the problem, consider getting an opinion from a different mechanic.
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