Need help - How to calculate gear ratio on mid drive?

[Dman12]

Hi, new here.
I am really confused. how do I calculate the gear ratio on a mid drive setup?
my motor has 11t sprocket, and it drives a 80t gear.

the 80t gear is attached to 48t gear of the bicycle which drives the 24t gear on the wheel.

so what exactly is the gear ratio? and can you please give me the way to calculate so I wont have to ask again.

Thanks.

 

[Tench]

If you can also tell us the outside dia of the wheel then you can calculate motor rpm at any speed.

Presently you will have 3.635 turns of the motor to 1 turn of the wheel.

80/11 = 7.27 turns of the motor to 1 turn of the crank, your wheel will do 2 turns to each rotation of the crank so 1 turn of the wheel equates to 3.635 turns of the motor.

 

[Dman12]

26" wheel, 2750rpm. 250w motor.

so if I understand correctly, I can change the 48 tooth gear to 24, and the ratio will stay at 7.27?
because now I must pedal to get things moving. I am not looking for speed (yet :lol: ), just to cruise around.

thank you!

 

[gwhy!1]

driven sprocket tooth count /drive sprocket tooth count = ratio

80t/11t= 7.27

to get total ratio
multiplay all the individual ratios

(80/11) x (24/48) = 3.63

higher ratio's reduces top speed but increases torque

 

[Dman12]

Perfect. thank you both for your help