Bicycle Mechanics - what's wrong with my crank/freewheel?
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04-06-11, 11:53 AM
My rain-bike/commuter is a 2006 R1000 (caad8) with a truvative gxp double and ultegra 9-speed. When I pedal, the slightest variation in my stroke causes "dead spots". I pedal and then there seems to be a "slackness" (?) in the stroke that is taken up as the chain reengages the drive train. I wish there was a more succinct way to put it. I don't remember it being an issue last year. I did have issues with the left crank arm getting loose last spring (a little lock-tight remedied it) so I wondering if the problem might be there or in the freewheel hub (crappy but relatively bomb-proof wh-r500). I do all the repairs on my bikes but I was hoping to get pointed in the right direction instead of doing a full tear-down/rebuild of my everyday commuter.
On a positive note, it have really helped me smooth out my stroke since it drives me crazy when it goes slack.
My other roadbike (2010 supersix with 6700) does not seem to have this problem.
04-06-11, 12:02 PM
Well, the cranks arms and BB are easy enough to diagnose. Just grab the arms and try to wiggle them sideways.
More than likely it sounds like your freehub is grunged up so that your freewheel pawls are not catching right away. You can back pedal and then snap it forward or you can remove the chain and do the same thing by hand to see if it misses catching or works OK. If it's a grease and grunge issue you may need to do this when it's cold to find the issue.
If it is the pawls that are lazy to engage then the fix is to strip the rear hub axle out and remove the freehub and dunk n' flush it with solvent until clean and then lube it with a mix of thick oil and solvent using a final dunk n' flush. Do NOT use a solvent and grease mix as grease when cold will prevent the pawls from snapping fast enough and you'll be right back where you started. Just use a nice thicker bodied oil such as chain saw bar oil or some rear end oil for cars.
Then put it back together with the proper grease in the bearing cups and you SHOULD be good to go.
04-06-11, 12:40 PM
yeah no play in the cranks. Looks like I'll be doing a tear-down of the freewheel this weekend then.
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