Originally Posted by
kcblair
I use gear inches. from
https://www.sheldonbrown.com/gear-calc.html.
That is the distance a bike rolls/moves forward with i revolution of the pedals. So, the shorter distance is your easier gear. Bike 1= 30 gear inches, Bike 2= 27 gear inches.
Hope this helps KB
To understand gear inches you have to go back into the history of the bicycle.
In the penny farthing days, a bigger front wheel meant you could pedal faster. The limiting factor was your crotch to pedal distance. When chain drive safety bikes were invented, riders were interested in comparing their drive ratios to the high wheeler bikes that they were used to. Gear inches is the factor they came up with and it persists to this day. A 100 gear inches would be equal to a high wheeler with a 100 inch front wheel.
Gear inches = chainring teeth divided by rear cog teeth times wheel diameter. To get how far you will travel with one turn of the pedals you have to multiply gear inches times pi.