How to shift derailer gears.
(It’s “derailleur”, but that’s French.)
This runs on for 850 words and seven drawings, so I hope you packed a lunch.
The drawings are not to scale, but they do use the same proportions in all the drawings.
The view is from the rider’s butt. You have an eye there, right? Well, my cat does.
So you are looking straight down from above the bicycle. At the front, at the top of the drawing, is the sprocket or sprockets on the crank, where the pedals are attached. We'll call this the “front sprocket(s)”.
At the rear, at the bottom of the drawing, are several sprockets on the rear wheel -- or only one sprocket if the bicycle has only one gear. We’re going with “rear sprocket(s)”.
My drawings go up to a 15-speed, which is all we need to explain the concept. That’s three front sprockets and five rear sprockets. Some bicycles have additional rear sprockets. With seven rear sprockets the total would be 21 gears (3x7). (The term “ten-speed” originated with… you guessed it: Two front sprockets and five rear ones.)
On my drawings, all sprockets (and crank and pedals) are black. GOOD chain positions are supposed to be green, but I’m out of green so they are BLUE. But BAD chain positions are definitely RED.
Here we go. The texts are below each drawing:
One front sprocket, one rear sprocket. The chain always runs straight. Stop reading now. Leave me that lunch bag.
FIVE SPEEDS (or maybe a slightly different number.)
One front sprocket and five (or so) rear sprockets. The chain runs straight in 3rd gear. It bends a little to reach 2nd or 4th, and it bends more to reach 1st or 5th. Note the angle of the outer blue lines. That’s the maximum bend we want to expose that poor chain to.
This is perfect for Burning Man, and for most other general riding.
15 SPEEDS – WITH CHAIN ON MIDDLE FRONT SPROCKET
Now we have the common arrangement of three front sprockets and five or more rear sprockets. This drawing shows the chain on the middle front sprocket, and you will notice that the chain can run just like in the drawing above. All I did here was add the two extra front sprockets, not in use. I'm sneaking up on something.
15 SPEEDS WITH CHAIN ON RIGHT FRONT SPROCKET
Now the trouble starts. Again I’ve drawn acceptable blue chain runs. And I have drawn a RED chain that illustrates EXCESSIVE chain angle. This leads to increased noise, increased friction, increased wear, and bad breath.
SOOOO…. What’cha do is this: Get out of bed in the morning, brush your teeth, and put the chain on the MIDDLE front sprocket. The front derailer is usually the shifter on the left side of the handlebar, but some manufacturers just have to “be different”. Leave the chain there in the middle. Throughout the day you shift gears as needed with the rear shifter, which is usually on the right-hand side of the handlebar.
ONLY if you hit a really bad patch of ground (or very steep up-hill) will you move the front of the chain to the inner (small) front sprocket. And ONLY after you have exhausted your options on the rear wheel – that is, the chain is already on the inner sprocket on the rear wheel. Think of this left front sprocket as your TRACTOR gear. Then, as soon as you no longer need the tractor gear, shift the chain back to the middle front sprocket.
SAME if you get to a long smooth surface and you want to set a speed record. First shift the rear to its outer sprocket. Then shift the front to the outer (large) front sprocket. Think of this as your ROCKET gear. Make rocket noises. As soon as you are no longer comfortable with this speed-demon velocity, shift back to the middle front sprocket.
DO NOT shift the rear gears while the front is in TRACTOR or ROCKET. At least not until you become an expert at this. Drawing #4 shows that it is all right to do so, up to the limit, but that’s for advanced riders. Normal people, INCLUDING ME, have no hope of keeping track of where the gears are if we don’t follow the basic TRACTOR and ROCKET concept. Half the bicycles that come in to Elliot’s Bicycle Service and Chardonnay Bar have the gears set like…
…this, which is the worst "cross shifting" you can commit. Then I’m suddenly out of wine.
Finally, there is something called HUB GEARS. In my father’s youth, he had a bicycle with two hub gears. Then for several decades the standard was three hub gears. Now there are rear wheel hubs with as many as 15 gears inside. From the outside, the bicycle looks like a single-speed. I like hub gears. They are reliable and easy to use. There is one shifter, and the chain never moves except round and round.
There will be a quiz at the 2013 ePlaya Meet-n-Greet.