Gear Ratios and wheel size
- Thread starter iksmudge
- Start date
Certainly it changes the ratio.
Here's how to calculate the amount.
http://www.sheldonbrown.com/gloss_g.html#gearinch
Here's how to calculate the amount.
http://www.sheldonbrown.com/gloss_g.html#gearinch
The 24" wheel bike will have a taller gear with the same 25/9 ratio. Larger wheels=more gear inches or more meters of development.
Basically, the bigger your damn wheel is, the harder your damn legs will have to work to push the same damn ratio.
Basically, the bigger your damn wheel is, the harder your damn legs will have to work to push the same damn ratio.
i ride 23/10 on my 24" and it is almost the same as 25/9 on a 20".
55.55555 gear inches vs 55.2
55.55555 gear inches vs 55.2
yep, its one of the easiest things to think about and often something people over look. gear ratio (25/10) X wheel diameter. keep in mind while 55 is considered "optimal" strength and riding style differ from person to person, so someone mainly dirt jumping will usually perfer a higher gear, while a street, or on a more extreme basis, trials guys, would perfer something lighter
exactly.
visualize it this way: if your front sprocket was the same size as your rear cog. like a 20t/20t, one rotation of your cranks would give you only one rotation of the wheel. the same as a unicycle. how far does one crank rotation move you? one circumference length of that particular wheel. (that's why wheel diameter is part of the equation). visualize a unicyclist with a bigger wheel going faster per turn of the cranks.
then by adding teeth to the front you are increasing the spins for the rear. a 2:1 ratio gives you two rear wheel rotations for every crank rotation. the reason the same gear ratio "feels" harder when on a big wheel bike versus a small wheel bike is simple physics (sir isaac newton). you're trying to move 200lbs from at rest to covering a longer distance with the same amount of leg force.
note that "gear inches" is not actually the same as roll out (the distance you go for one rotation of the cranks). i used to mistakenly think it was the same thing.
see http://www.sheldonbrown.com/gloss_g.html#gearinch
http://en.wikipedia.org/wiki/Gear_inches
"Gear inches is a system that assigns numerical measurements to bicycle gear ratios, to indicate how low or high a gear is.
Gear inches has no current physical significance; it corresponds to the diameter in inches of the main wheel of an old-fashioned penny-farthing bicycle with equivalent gearing. An alternative gearing measurement is metres of development, which corresponds to the distance in metres traveled by a bicycle for one rotation of the pedals. To convert from gear inches to metres of development, multiply by 0.0254π (often rounded to 0.08)."
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