Braking on a Mountain Bike

Bend, Oregon: Biking, Climbing, and Beer

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Here's a bit of physics to think about the next time you slam on just your front brake while riding quickly down a steep stretch of trail. Of course, you'll have to think fast since you'll be leaping over your handlebars headfirst into the dirt, but fortunately the scientific principle is succinct: A body in motion tends to stay at uniform motion in a straight line unless acted upon by an outside force.

Got it? Good. Now nod your thanks to Isaac Newton (that is, if you're still conscious) for developing his First Law of Motion. And thank your lucky stars that you were wearing a helmet.

Had you been paying attention in high school physics you might have avoided the headplant, but if you aren't too scrambled there's still time to learn how to apply Sir Isaac's musings to your mountain bike techniques. Let's think for a moment what happens when the brakes are applied. (1) The bike stops. (2) You don't. Nice and simple, huh? Well, it is, really, when you stop to think about it. Which is exactly what so many riders don't do until they're forced into it by the school of hard knocks.

Now, the bike has stopped because it has been acted upon by an outside force called "the brakes." Unfortunately, since you are much heavier than your bike and were traveling at the same rate of speed, a lot more is required to keep the heaviest part of you (your trunk, or "center of mass") from propelling all of you over the bars. So let's go over what can be done to keep you bike-bound.