Is it moisture/slush in the freewheel that is not evaporating because I have to keep the bike outside all winter? Then it might freeze when the temperature goes low enough. How long would it take to evaporate if inside at room temperature?
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To be clear, it engages fine in warmer temps? And you're sure its a freewheel rather than a freehub? – Batman Feb 21 '16 at 17:39
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Try to avoid leaving your bike outside - its a hard life outdoors for anything mechanical. A shed or garage is better than a carport, which in turn is better than outside unprotected. – Criggie♦ Feb 22 '16 at 10:56
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From the OP: Its a freewheel. Had the same problem on another bike in extreme cold. Can't bring it in - no space and uncooperative landlord. I feel sorry for the bike out there all winter in the cold! Then again, maybe the temperature variation from -25c to +20c might be bad as well. Opinions on that? – Bob Feb 22 '16 at 19:54
If the pawls will not engage the wheel will not engage.
It could be moisture freezing. More likely the grease is just more viscous (sticky) at lower temperatures. If you really have a freewheel (not freehub) then it is likely not serviceable. If it is serviceable then break it down and clean it. There is grease for bicycles and also low temperature grease. For sure you do not want to use a generic axle grease that is designed to handle high temperature. Use a light (low temperature) grease and accept you will need to service it more often. Use a lot to not give moisture as much room.
If it is a non-serviceable freewheel you might free it up with WD40 but that is not really a long term solution as WD40 is more a solvent than lubricant.
There are variations but this is the basic design
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Interesting graphic. It does seem to be moisture freezing as you said. In the graphic, what's the difference between the triangle points and the circled points? – Bob Feb 22 '16 at 19:56
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Seems to be half pitch engagement. the green circled pawls are not locked in. Rotate 1/2 a tooth pitch and they will be while current set won't be. Cool engineering to get less distance to contact – Warren Burton Feb 22 '16 at 20:08
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@Bob Actually I suggested not moisture freezing. "Could be" was more just a polite introduction. – paparazzo Feb 23 '16 at 4:23
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Frisbee....what else could it be? Very predictable at cold temperatures and with multiple bikes with different freewheels. – Bob Feb 23 '16 at 7:01
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@bob "More likely the grease is just more viscous". If was freezing it would happen at 32 F. – paparazzo Feb 23 '16 at 10:45
