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Braking & Steering

Brakes have improved as materials and engineering know-how have evolved. The earliest bicycles lacked brakes, which added to their daredevil reputation. For bikes to become more popular an effective mechanism for slowing and stopping had to be devised. All brakes, regardless of the mechanism, share one thing in common--they increase the amount of friction (usually on the wheel) allowing the rider to slow or stop. Steering a bicycle has remained a constant. While handlebars have evolved, the fundamentals of steering and controlling a bicycle haven't changed. But recently our understanding of the science behind steering a bicycle has.

Missy going downhill Women's Downhiller Missy Giove depends on quick reflexes and cutting edge technology. Downhill racing is perhaps the most dangerous of all cycling sports. More on Missy on Page 2 of this section.

IMAGE COURTESY OF CANNONDALE BICYCLES

Take the Plunge

The first widely used braking system was know as the plunger. It first appeared on the high-wheelers of the 1800s. The principle of the plunger brake is simple: by pressing down or pulling up on lever, a metal shoe is pressed against the outside of a tire creating friction and slowing the bicycle down. The problems with this system include excess wear on the tire (it doesn't work well with pneumatic tires, even when the metal shoe is covered with rubber) and poor performance on wet surfaces. Water decreases the friction between the brake shoe and the tire, lessening the braking power.

Coaster Brake

The coaster brake is still in wide use throughout the world and appears in a number of less sophisticated bicycles like cruisers and utility bicycles. Coaster brakes also appear on some children's bicycles and tricycles. The coaster brake works by reversing the motion on the pedals. The brake mechanism is inside the hub of the wheel and pushes outward on the hub, creating friction and slowing the bike. This brake is particularly strong and tends to "lock up" or skid the rear wheel when engaged.

Coaster Brake
A coaster brake on an old "cruiser" bicycle.



Caliper Brakes

The most popular brake for road and mountain bicycles is the caliper rim brake. The cyclist engages these brakes by pulling on levers which pull cables, forcing pads or shoes against the inner rim of the front or rear wheel. Caliper brakes are lightweight and inexpensive but they are not without problems. During wet weather it may take twice the distance to stop as it does in dry. The water acts a lubricant on the sides of the rims. During very long downhills the rims can heat up, even to the point of melting a hole in the tire's inner tube!


When using caliper brakes, riders are advised to place gentle pressure on the brakes and modulate in a controlled fashion. Controlled modulation will help brakes perform better, particularly in wet weather, by removing some of the excess liquid from the rims. In addition, pumping the brakes will ensure the rider does not lock-up the brakes (when the tires stop spinning, the cyclist begins to lose control over the bicycle). Exploratorium Senior Scientist, Paul Doherty explained, "I balance the braking between the skidding the wheel on the ground and the skidding of the brake blocks. If I go into a skid so the wheels aren't spinning, I don't have control when I point the wheels of the bicycle. Just like the anti-lock brakes on a car, I want to keep that wheel rolling a little bit so I can steer and control the bicycle."

Paul Doherty RealMedia Clip
Paul Doherty talks about braking.

Balancing the braking between the front and rear tire is also important. Paul explained, "The most important things about stopping are that you want to stop quickly, in control, and not go over the handlebars. As I'm going along on the bicycle and I apply the brakes, my body has inertia and it still tends to go forward. That shifts my weight forward onto the front wheel. So, I do a lot of braking with the front wheel, but if I do too much braking with the front wheel, then I wind up going over the handlebars. So the idea of the braking the bicycle is to balance the braking between the front and the back to get the maximum braking."

 

U.S. Women's cross-country champion, Ruthie Matthes sees planning as a key to effective braking for many of the reasons that Paul cited. Ruthie told us, "We have the fortune in our racing to be able to pre-ride the courses so we can plan our braking." Ruthie continued to explain her technique for braking on sharp turns. "What I do when I'm racing, if I'm coming into a sharp corner I'll brake ahead of the corner, and as I'm going into the corner release the front brake and only use the rear brake."

Ruthie Matthes

RealMedia Clip
Ruthie Matthes talks about her techniques for braking.

 

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