# Formula for calculating rolling resistance #### Franklin

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A formula for calculating rolling resistance is N = W x V x T / 270 where N
is the horsepower required, W is the weight in kilograms (2.2 lbs = 1
kilogram), V is the speed in kilometers per hour (62 mph = 100 kph), and T is rolling
resistance of the tire. Typical values for T are 0.015 on concrete, 0.025 on
crushed rock/asphalt, and 0.05 on dirt road. At its best Bonneville has a T
value of about 0.02 while under wet or sloppy conditions it can be 0.04 or 0.05.

For example, under sloppy conditions at Bonneville a car weighing 4,400 lbs
(2,000 kilograms) moving at 310 mph (500 kph) would require 2,000 x 500 x .05 /
270 = 185 horsepower to overcome rolling resistance, while at 400 mph (645
kph) it would require 2,000 x 645 x .05 / 270 = 238 horsepower. Under dry
conditions at Bonneville that same car would require only 2,000 x 645 x .02 = 95
horsepower to overcome rolling resistance at 400 mph.

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