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Old 12-01-2008, 10:46 PM
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Prasinos Prasinos is offline
Motorized Bicycle Elite Member
Join Date: Dec 2008
Location: CT
Posts: 257
Default Re: Your opinion on top speed/RPMs

I made a model on excel using very conservative numbers calculating the coeficient of drag, rolling resistance of a road bike tire, and assuming 100 percent drivetrain effecientcy with a gear ratio set to run at rpm of maximum power for the motor. you would still need over 7hp to reach that speed on flat ground. That is also assuming you are riding with a road bike, tires inflated to 100 psi with your hands on the drop bars.

If you weigh around 220 lbs as I do, this would mean you would need to be riding down a hill. By my calculations to gain the 4.8 hp to reach your 54 mph speed you would need to be riding down a 17 percent grade at least. Not to mention it would need enough distance to allow you to accelerate and decelerate, I would think by using the breaks to the tires limits you would experience some fade in breaks as your pads melted.

Remember these numbers are all theoretical with ideal conditions. Also, I have gone 40-45 mph on an unmotorized road bike down hills, and it is scary the handlebars and frame shake violently and just touching the breaks is intimidating. I wouldn't recommend it. Chance of death, approximately 1 percent.

Last edited by Prasinos; 12-01-2008 at 10:48 PM.
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