Getting a Little Shifty

Ugh, another break that was entirely too long. However, I have not forgotten about this blog, just busy with other things (jobs, life, etc.). I am riding again, although I did take last week off because I over did it the week before and ended up with a very painful cramp in my right calf. (Sounds like another blog entry to me.) Anyways, today I want to shift gears and talk about shifting gears (literally).

Now, unless you have either a single speed bike or an internally geared bike, you have the standard front and rear derailleur configuration. Most people tend to stick with only a handful of gears, often times at the lower end because their bike isn't properly adjusted to their body, but that's another topic. Many people (Americans, especially) like to buy bicycles with lots of gears thinking that "more is better". Well, not necessarily so. Consider this, the typical mountain/hybrid bicycle has a triple chainring up front and an eight or nine speed cassette in the rear, giving a total of 24 or 27 gear combinations. However, not all of those combinations are usable and many are either duplicates or close enough that it makes little or no perceived difference.

Let's take my bike for example. I ride an older Specialized with a triple chainring with a 30/40/50 combination and a seven speed freewheel with a setup of 12/14/16/18/21/24/28. So that should give me 21 speeds, right? Wrong! Out of the 21 speeds, there are three combinations that are duplicates (I'll illustrate that in a minute), four combinations that are unusable due to the resulting chain angle (one of which is also a duplicate mentioned above), and one where the difference is minor.

To better illustrate this, I am using the late Sheldon Brown's on-line gear inch calculator. Since I ride with a 700C x 38 wheel, I factor that into the calculator, along with my 175mm crankarms and get the following gear inch table:

30 33.3 % 40 25.0 % 50 12 68.3 91.1 113.8 16.7 % 14 58.5 78.1 97.6 14.3 % 16 51.2 68.3 85.4 12.5 % 18 45.5 60.7 75.9 16.7 % 21 39.0 52.0 65.0 14.3 % 24 34.2 45.5 56.9 16.7 % 28 29.3 39.0 48.8

The following gear combinations are duplicates: 30x21 and 40x28; 30x18 and 40x24; 30x12 and 40x16. The following combinations are unusable because the resulting chain angle would cause rubbing on the front derailleur and excess lateral flex on the chain: 30x14, 30x12, 50x28, and 50x24. (Note that 30x12 is both a duplicate and an unusable gear.) The gear combinations 30x16 and 40x21 are less than one gear inch apart, so the difference is imperceptible.

A gear inch, for those who don't know, is defined as the number of inches traveled for each revolution of the pedals, and dates back to the old penny-farthings. Most people don't concern themselves with gear inches any more, but it can be useful for devising a shift pattern.

Again, taking my bike as an example, I use twist shifters rather than trigger shifters, but both have numbers that correspond to the respective gear from low to high, so this should translate to other bikes. I printed out the table above, crossed out the unusable gear combinations and highlighted the duplicates. Next, I numbered the chainrings and cogs from low to high to match the numbers on my shifters. Then I opened up a spreadsheet program and created the following shift table:

1-1	1-2	1-3	1-4	1-5
		2-1	2-2	2-3	2-4		2-5		2-6		2-7
						3-3		3-4		3-5		3-6	3-7

Note: The number to the left of the hyphen denotes the left shifter number (or chainring) and the number to the right of the hyphen denotes the right shifter number (or cog).

As you can see, I have three combinations that are (more or less) duplicates, therefore they are listed as being equal on the shift table. I left this as such in case I find myself in the lowest chainring for extended periods of time (like hills or strong headwinds). Otherwise, I start with the combination of 2-1 and start my shift pattern from there. I can now take this shift table, print it out, and tape it to my handlebars as an easy reference (and less memorization).

To use the table, I merely start out with a gear combination (normally 2-1) and shift from left-to-right to upshift, and right-to-left, to downshift. So, a normal upshift pattern would be 2-1, 2-2, 2-3, 2-4, 3-3, 2-5, 3-4, etc. Whenever extra torque is needed (such as strong headwinds, climbing hills, etc.), I'll start with 1-1 through 1-5, then shift to 2-4, 3-3, and so forth. This allows me to shift to each successive gear (according to gear inch) without making a massive jump that could sap my strength and energy in the long run and help maintain my cadence.

Bicycle Accidents and Fatalities Statistics

I always say that bicycling is a easy, healthy and safe way to commute to work and to run errands. However, there are those who claim that bicycling, especially in this area, is anything but safe. After a little research, I was able to come up with some interesting statistics that help support my claim.

The National Highway Traffic Safety Administration (NHTSA) recently released their 2007 Traffic Safety Fact Sheets. Among the reports is one that addresses bicyclists and other cyclists. The report states that there were 698 cyclists killed and 43,000 injured in traffic crashes. The numbers sound alarming until you realize that cyclists account for only 2% of traffic fatalities and injuries during this time period. The total number of traffic fatalities for 2007 was 41,059 out of a population of 301,621,000. Of those, 698, or 1.7%, were cyclists. That gives a ratio of 2.31 cyclists killed per one million people. That is slightly more than 1 cyclist killed out of 500,000 people. Your odds of being killed on a bicycle are better than being dealt a straight flush (1 in 72,193.33 ), but less than being dealt a royal flush (1 in 649,740).

Now lets consider the data from Fatality Analysis Reporting System (FARS) for motorized vehicles. For 2007, there were 37,248 fatal motor vehicle crashes resulting in 30,401 deaths. That results in 123.49 fatalities per one million people. That means you are 53 times more likely to die in a car accident than you would be killed riding a bicycle.

Now, back to the bicycle injuries and fatalities for a moment. The highest fatality rates where male riders between the ages of 45 and 54 (132 killed, 6.11 fatality rate). Among female riders, the highest fatality rates where in the 35-44 age group (18 killed, 0.84 fatality rate). The highest injury rates were among male riders between the ages of 10 and 15 (8,000 injured, 614.6 injury rate) and among women, it was the same age range with 2,000 injuries and an injury rate of 130.9. The injury rates are high, but taken into consideration the age group in question, it is not alarming or even surprising. After all, this is the age group that is most likely to be involved in BMX, youth mountain bike racing, and general reckless behavior.

According to these data, the location of accidents is almost evenly split between intersections and non-intersections for ages between 10 and 20. Cyclists in the 21-24 age group are three times more likely to be hit at non-intersections than at intersections. For ages 21 and over, the number of accidents at non-intersections outweigh the number of accidents at intersections. The number one reported factor in bicycle accidents is the failure to yield the right of way (20.9%). No reported factors accounted for 37.5% of bicycle accidents, so no reliable way to determine the causes of these accidents. Time of day seems to have little effect on the number of accidents. However, there is a significant increase in the hours between 3:00 p.m. and 8:59 p.m. I am merely guessing here, but that includes the afternoon rush hour traffic and, during the fall to spring, the setting of the sun, both of which may play a factor. Also of interest, light trucks, including SUVs, account for the majority of bicycle related accidents (297) with passenger cars coming in second (242).

Yes, there are risks with riding a bicycle, but the same is true of most every activity from washing dishes to skydiving. There is no way to eliminate all risks, but much can be done to mitigate the risk factors to a reasonable and manageable level. The first and most obvious is to wear a helmet. I know that there is a debate about the effectiveness of helmets to prevent all injuries, but the fact is helmets do help prevent many head injuries that would be otherwise fatal or debilitating.

However, helmet use alone does not make a bicyclist safe, or even safer. Learning proper riding style and obeying the rules of the road plays a much bigger factor to being safe on the road, as does being visible. Headlights and tail lights, reflectors, and brightly colored clothing will help drivers see you better, especially at night or low light conditions (e.g., riding on a tree shaded road). Choosing appropriate routes (e.g., less motorized traffic, slower speeds) will lessen the number of possible incidents. Use of hand signals for lane changes, turns, and slowing/stopping helps you communicate with drivers, as does proper lane positioning. Also, be aware of the most common hazards and how to avoid them.

And to quote Sergeant Esterhaus from "Hill Street Blues", "Hey, let's be careful out there."