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Treebeard's Stumper
15 March 2002

Gearing Up For a Ride

Winter is turning into spring. It's a perfect time to tune up your bike and go for a ride! The most confusing part of biking for kids is surely the gears. My old mountain bike has 3 chain wheel gears in front that turn with the pedals and have 28, 38, and 48 teeth. I also have 7 freewheel gears in back with 13, 15, 17, 20, 23, 26, and 30 teeth. That makes 3 x 7 = 21 combinations. How does this work? What is the shifting pattern from low (for climbing) to high (for cruising)? Which gear combination is in the middle? Would even more gears make biking easier?

This is a live image map. Click on a bike part name to get some good practical info from UtahMountainBiking.com. Bicycles are efficient and elegant machines, but they are only "simple" for an engineer. Kids find the gears complicated, but I'm more confused by the hidden bearings in the headset and the bottom bracket. By the way, this bike is way too clean to be mine! The real stumper is to understand your own bike. I put a paper clip on one gear tooth of each cog and counted my way around one by one. Then find your calculator and figure the gear ratios.

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Copyright © 2002 by Marc Kummel / mkummel@rain.org