# Bicycle Mechanics - gear ratio question

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exas
06-28-07, 11:09 PM
is there a difference between say 40/20 and 60/30? is one easier to pedal than the others?

roadfix
06-28-07, 11:17 PM
Difference in efficiency, if any, is probably insignificant, but your drivetrain components will last a little longer with the 60/30.

urbanknight
06-28-07, 11:24 PM
I've heard it said that larger gears are more efficient, but it's probably a minimal difference.

cyqlist
06-29-07, 07:45 AM
The smaller the cogs, the more the difference in efficiency and wear. The difference between 30/15 and 40/20 would be more than the difference between 40/20 and 60/30. Also higher stresses on the chain and cogs, and on the frame too with smaller cogs. When I set up the drivetrain on my PBW with Rohloff hub and 20" wheels I opted to go with 52/15 rather than 45/13 partly for these reasons (there is no 14 tooth cog for Rohloff).

exas
06-30-07, 03:07 PM
does someone have a definite answer here?

caloso
06-30-07, 03:14 PM
According to Sheldon's gear calculator

60 x 30 = 52.6 gear inches
40 x 20 = 52.6 gear inches

Obviously the ratio is the same, 2x1, for each. There is a theory that the greater number of teeth spreads the wear and is mechanically more efficient. I don't doubt the theory but I think in practice, the difference would be too small to notice.

CdCf
06-30-07, 05:17 PM
The tighter the bend for the chain (i.e. the smaller the sprockets), the larger the angle each link has to rotate. Rotating any chain link means working against friction within the link, wasting energy. The less rotation, the less energy wasted, I would think.

San Rensho
06-30-07, 05:41 PM
If you were blindfolded and pedalled one then the other (and didn't crash), there is absolutely no way you could tell if you were riding the 40 or the 60.

Efficiency would be based on which one has the most friction loss, I'm not going to speculate.

rhenning
06-30-07, 08:20 PM
You bike will be heavier with the 60 as you need a longer chain to operate that gear set. Other than it is insignificant and almost impossible to measure the difference. Not even sure the weight would be measurable. Roger

JanMM
06-30-07, 08:45 PM
Wallet will be lighter with 60T versus 40T.