Piston Legs of a human machine.?
My racing bike has 9 rear sprockets and two front sprockets. The rear set is 12, 13, 14, 15, 17, 19, 21, 23 and 25 toothed. The front ones are 54 and 42. I use size 23c tires. My cadence can range from 80 - 93 rpm.
Find me a gear combination that will give me a speed close enough to 60kph that is also close enough to my average cadence.
Let me think!A 700c rim is 622 mm across the "bead seat". Bicycle tires are nearly circular in cross section so the nominal width is also the height. For a 700c wheel with a 23 mm tire, the diameter would be very close to 622+(2*23) = 668 mm. Then the circumference would be 668*Pi (3.14159....) = 2098.6 mm. So that's where the recommended 2100 came from.
Since you are looking for a speed close to 60kph
We try using your biggest to smallest gear combination.
Ratio: 54:12 = 4.5 / rev of large sprocket which is 1rpm
taking average rpm : (80 + 93)/2 = 86.5 say 86 rpm for lighter pedalling
86(60) x 4.5 * 2100/(1000X1000)= 45.01 kph which is short of the requirement:
We make 86 variable and fix the speed at 60:
x(60) x 4.5 * 2100/(1000X1000)= 60kph
x = 105.82 rpm
You are not anyway near
The maximum speed you can achieve with your cadence and top gear is:
93(60) x 4.5 * 2100/(1000X1000)= 52. 73 kph
You need to train more and raise your endurance and explosive power together.
Front Wheel Drive Motorbike By Bessette
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