Brakes

Ask 100 people what bicycle brakes are for, and likely 99 of them will respond with a blank look and then say,  “For stopping.”

Well…  yes.  But there’s a bit more to it than that.

A brake is a device that converts kinetic energy to heat.  Roughly (and very loosely) a cyclist in motion has a kinetic energy.  This energy can be measured and is equivalent to E = ½ mv².  In that equation, E is the kinetic energy, m is the combined and total mass of the vehicle (cyclist + bicycle), and v is the velocity at which the vehicle is traveling.  (Please take a deep breath and relax!  We’re not going to turn this into a Physics lesson.)  The important thing to remember here is that two things affect the kinetic energy.  They are the mass of the vehicle and its speed or velocity.  Of these velocity has a much greater effect.

There are a great number of situations where a cyclist would want to decrease velocity without stopping.

Examples abound.  Here are a few:

• I’m going to fast to make that turn!
• That truck won’t be out of the intersection before I get there!
• I’m going as fast as I can, and that idiot Honda is moving into my lane!
• I can’t hear what my riding companion is saying, and she is the one who knows how to get home.
• I’m going too fast to read the street signs, and there is an important turn coming up.
• If I go down this mountain much faster I risk becoming “street pizza”!
• Yipe!  They stopped pedaling!

Personally, I’m not fond of braking.  I prefer to make my ride fluid, using deceleration  only as needed to adjust the line in a curve, or to make necessary full stops at intersections.  Sometimes, when riding with others, I find it necessary to brake, just to stay in contact.  It’s a mild annoyance.

There are those times…  The ones when we are following someone up a hill, and they, for no apparent reason, abruptly slow down so much that we must apply brakes, while climbing.  Lordy!

Most folks don’t pay a lot of attention to their bike brakes…  until they stop working.  Fortunately these devices are fairly reliable.  That wasn’t always the case.

When the Tour de France race started, in the very early days of the 20^th century, all the bikes were fixed gear, and rim brakes were still a thing of the future.  Oh there were bicycles with brakes, but these were deemed too heavy and too clunky for serious racing.

The early Tours did include significant climbing sections, but mountain descending was not a feature.  The advent of the first rim brakes made two things possible.  A cyclist could mount a lower gear on the bike for climbing purposes, and freewheels became practical.  Still, those early brakes weren’t much.  Remember, the rims of racing bicycles were made form bent wood.  The first rim brakes were crude, “single-pull,” and the pads were a sticky laminate of leather and tarry rubber.

I have ridden authentic reproductions of those early bikes.  I can state that the brakes were only slightly more effective than dragging one’s feet along the ground.  By the late ‘40s metallic rims and rubber had improved things considerably.  Road bike brakes were then up to the level of miserable performance.  That’s where things stayed for a while.

When I first got into road riding, the best that we could obtain worked only fairly well.  A good set of roadbike brakes, with the best pads available, was good for three hard applications,  they heated too much and faded to near useless.  And rain?  Fuggedaboutit!

Today’s brakes, road or mountain, are marvels.  And, like it or not, disc brakes are coming for the lightweight road bikes.

A bit of wordplay:

To Brake = to slow down.

To Break = to damage beyond function

I braked = I slowed down or stopped.

I broke = I damaged beyond easy repair.

I braked hard, and the brakes broke, and then I got all broke up.

SPOKE

I spoke to him yesterday.

I am choosing a new spoke to repair that wheel.

What kind of spoke do you like best?

How does a spoke work?

We’ve had the wheel for a long long time.  It’s been with us so long that we have no idea who invented it.  But we do have some idea about where and when some refinements were added.

Earliest wheels were used on carts or wagons.  They were simply boards, bolted or pegged to other boards at a 90 degree angle, and then the whole works cut at the ends until it was round.  This makes something that will roll, but it can be improved upon greatly.

Some early improvements were made by the Andronovo Culture, of western Siberia.  In about 2000 BC, these folks figured out that most of that big solid wheel wasn’t needed.  They invented the Spoke.  Turns out that a spoked wheel is lighter and stronger.  We are here talking about a wooden spoke.

In the case of wood spokes, the spokes are loaded in compression.  That is, the weight presses down on each spoke, in turn, at the bottom of the wheel.

Incidentally, the word “spoke” comes from the method of manufacturing the product.  A tree, after cutting was split lengthwise into four to eight sections.  These sections were called spokes.  Because they ran lengthwise, in the same direction that the wood of the tree supported the weight of the tree, they were ideal to be formed into things that supported weight…  Like the spokes of a wheel.  The tool that was used to form the tree-spokes was called a “spokeshaver.”  Eventually, the product came to be named for the material it was made from.

The wood spoke lasted a long time.  The “wire spoke” It wasn’t until the middle of the 19^th century.  It is significant in that it is no longer compression loaded.  “Wires” or “spokes” of drawn steel were attached to the hub and the rim and tightened.  This formed a “wire wheel.”  In the wire wheel, the spokes are loaded in tension.  The load literally hangs from each spoke in turn, with the load distributed around the tensioned rim.  It is this technique that makes the modern bicycle wheel.

Since steel has a terrific tensile strength (you can pull on it real hard before it breaks) it is possible to make a wheel of this type that is both enormously stronger and many factors lighter than one that has to rely on compression of a wooden spoke.  If we had to rely on wooden compression loaded spokes, each of our bicycle wheels would weigh in at about 25 pounds.  (I can’t imagine that riding such a beast would be a lot of fun.)

Our spokes support us.  They carry our weight by hanging it from the rims of our wheels.  They hold the wheel in shape, and they take the loads from our cornering, accelerating, and braking.  Each one of these marvels weighs only a few grams.

When was the last time you thought of your spokes, or gave them a “thank you”?