The Steel Steeds

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Thursday, July 29, 2010

Do The Math

The ride began with the first pedal stroke. So you can better appreciate the stroke aspect of the ride and a few other related topics, I thought I'd do the math for you.

First you have to understand the general parameters of multi-geared bike. Our bikes have 700 cc wheels, roughly 27" diameter.  We have 3 cogs in the front called chainrings and 9 cogs in the back called the freewheel. When the chain is in the largest chainring you are in a high gear. Lowest chainring is a low gear. As you know the cogs have teeth. The three chainrings are 48/36/26 and the nine cogs in the rear go from 11-32 (11 - 12 - 14 - 16 - 18 - 21 - 24 - 28 - 32 teeth).  If you divide the number teeth on a rear cog into a chainring you get gear inches (48/12=4x27 (diameter of the wheel)=108 gear inches. That is equivalent to a wheel with a diameter of 108 inches. To determine the distance traveled you multiply by pi or 3.14. Therefore, with a 108 inch wheel the bike would travel 339.12 inches. You can determine your speed by dividing 5,280 feet (63,360 inches) by 339 inches equals ~187 strokes. Divide this number my minutes (3, 4 etc) and you get the number of strokes per minute you would have to pedal and your speed. So, 3 minutes would be 20 mph and you would have to pedal 62 strokes per minute. Easy right?

Now we are riding approximately 3,000 miles and a 27 inch wheel has a circumference of (27x3.14) 84.78 inches.  There are 63,360 inches in a mile. Therefore, our wheels rotate about 745 times per mile and will rotate 2,235,000 times by the time we're done.

Now the good part. Lets say our average cadence is 80 revolutions per minute. In one hour it would be 4,800 strokes. In five hours it would be 24,000 strokes, our average day. In our first 26 days of riding our feet went around 624,000 times. I'm averaging on the low side. By the time we're done we will have made over 1,300,000 strokes.

Rosie said, "Can you say rock hard buns?"


  1. ok...I was speed reading that entry and my eyes still rolled into the back of my head!~