## What torque is needed to make a bicycle move.

Hey Im starting an electric bike project and I need to know how much torque is needed to get a bike going from a stationary position in ft/lbs in first gear that has a gear ratio of .93? What do you guys think?

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 I think you have an average weight of people, the weight of the bike, the gear ratio, the size of the driven wheel and the length of the lever arm on whatever means of power you intend to use...
 I think you have an average weight of people, the weight of the bike, the gear ratio, the size of the driven wheel and the length of the lever arm on whatever means of power you intend to use... Ive been using an old huffy that is in pretty good condition. Ive been using around 300 lbs as the weight. In first gear the gear ratio is 1:.93. the drive wheel (smallest chain ring) has a 5 in diameter, and im going to be a direct drive from motor to the drive shaft. The motor im using is a 48 volt 750 Watt motor, which produces around 25.35 ft/lbs. I found a few good formulas online that dealt with "burning rubber". Those help me get a better idea of what it takes to beat the COF of rubber vs pavement which is (.75 N) so it states: F= MA F= (136.08 kg)(9.8 N/kg) = 1333.58 N F(normal) = 1333.58/2 = 666.8 N F (friction) = (.75)(666.8N) F= 500.1 Torque = radius * force 26 in wheel means the radius is .33 Meters T= .33 * 500.1 T = 165.033 Nm which equals 121.72 Ft/Lbs So if you take that and factor in the .93 gear ratio I believe that to "burn rubber" you need to have a motor that can produce 113.20 Ft/Lbs Does that make sence? are my numbers flawed what do you guys think?

## What torque is needed to make a bicycle move.

Remember it is a BIcycle, so the weight is distributed some. Yea. You will need a ton of torque for a 300lb guy to peel out while sitting on a bicyle...

 ya that is a lot or torque, and the 300 lbs is the guy and all the batteries and the bike and the motor thats a total mass. I then did the calculations for just the bike which is about 100 lbs and it came to a little over 40 ft/lbs of torque.
 Go out to the bike and sit on it with the front pressed against a wall. Put your foot on the pedal and see if you can get the tires to spin while sitting down. You've got a 6-7" lever on the flywheel and the strength of your leg. You will find it extremely difficult to spin those tires.
 your right it is a hell of a lot or torque which is why im questioning the formulas that I found.