Back wheel slows no brake
10-06-15, 07:18 PM
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Back wheel slows no brake
Just assembling a bike. I pushed down on the pedals whilst back wheel was on the floor and it seemed to tighten the freewheel cog. However now the back wheel turns but instead of spinning freely, it slows down after 10 seconds. There's no brake attached yet.
Any ideas what to do?
Any ideas what to do?
10-06-15, 07:38 PM
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Tight hub bearings ? Tire lightly rubbing the frame ?
Or maybe nothing's actually wrong ?
Or maybe nothing's actually wrong ?
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10-06-15, 09:24 PM
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Nope not rubbing against frame. Shouldn't the wheel spin freely for a long time after stopping pedalling? It seems like something has resistance on it.
10-06-15, 09:29 PM
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Some cup and cone hubs are assembled with bearings too tight. Some sealed bearing hubs have friction from the seals. If you remove the wheel and turn the axle by hand you can get a better idea if there's a problem or not.
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10-06-15, 09:36 PM
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The amount of time an unloaded wheel spins varies tremendously, even when all is perfect. Things like the viscous drag of the grease used, friction from seals, and the design of the freewheel ratchet system all can make a big difference. Perversely, lighter wheels, especially wheels with lighter rims and tires slow fastest because of the reduced inertia.
BUT
All of that is totally meaningless because what you;re seeing as a big difference only seems so because there's no inertia in the system. The wheel weighs maybe 2#s, but the entire bike with you on it will be neared to 200#s. So a 30% difference now, will make an actual difference of 30% of 1% when all is said and done. In the real world, the bike's sources of drag or friction are, in order, air resistance, tire rolling resistance, chain drive inefficiency (may be higher than tire drag), then all else combined comes in last.
My advice, don't obsess. Finish the build, ride the bike a while, then recheck this stuff if it still bothers you.
BUT
All of that is totally meaningless because what you;re seeing as a big difference only seems so because there's no inertia in the system. The wheel weighs maybe 2#s, but the entire bike with you on it will be neared to 200#s. So a 30% difference now, will make an actual difference of 30% of 1% when all is said and done. In the real world, the bike's sources of drag or friction are, in order, air resistance, tire rolling resistance, chain drive inefficiency (may be higher than tire drag), then all else combined comes in last.
My advice, don't obsess. Finish the build, ride the bike a while, then recheck this stuff if it still bothers you.
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10-07-15, 08:02 AM
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My singlespeed has cheap hubs that can easily be overtightened and you need to back them off a bit to get them to spin freely.
