It's a dew point calculator.

I know that's not what it is but figured I'd be the first one to make himself look stupid. Now others can weigh in with legitimate guesses.

I bet it's some sort of actuarial table.

OK, now I've made myself look stupid too, Jim. I've even made myself look boring! But it's Sunday -- nothing else to do.

There's no such thing as a stupid guess. However, there is such a thing as a wrong answer. ;-)

Let's see...think, um, more engineeringly, or perhaps, more mechanically...

It's an actuarial tire pressure guage. No?

OK, I can see that another clue will be needed. Of course, Lance wouldn't need another clue; he'd know.

Was that supposed to be our clue? Who's Lance? Lance Armstrong?

The numbers appear to be along the line of frame sizes and wheel sizes...maybe it's used to determine the number of spokes needed on a wheel? Does it have something to do with torque? I'd like to buy a vowel...

I don't want to derail your train of thought, Gwynne, because you're on the right track...but you still need to gear it up a notch.

I sense a bunch of clues in all that "derailing" and "gear" talk, but it will take a more knowledgeable cyclist than myself to figure it out. I bet Jen's Beau knows...

It's an amount-of-torque-required-per-gear-size thingee used to make derailleurs.... Ok, I'm still clueless.

Numbers make me sneeze anyway...

It is a gear inch ratio table!

It is a gear inch ratio table!

Excellent! (She's a runner...but she could also be a cyclist.)

The chart shows the distance a bicycle will travel for each revolution of the pedals, based on the selected combination of gears. The top row of numbers represents the number of teeth on the rear sprocket (aka the cogset); the left column is the number of teeth on the front gears (aka the chainrings). The numbers in the chart show the inches the bike will travel based on the combination of those gears.

Thus, if the bike chain is on a front sprocket with 30 teeth and on the rear sproket with 18 teeth, it will travel 45" during each pedal revolution.

Gear charts -- or at least the understanding of the various ratios -- are a big deal for serious cyclists who want to tailor their drivetrain to their riding goals or preferences. Even with up to 20 speeds for a racing bike or 30 speeds for a touring or mountain bike (which have three chainrings up front), it's sometimes hard to find just the right gear for the riding conditions. Also, some combinations of gears are redundant (the gear-inches overlap) and others are unusable (due to the strain on the chain).

For riders like me, however, they're just an academic exercise. And for you, I suspect they're just another example of how the boringly trivial can get elevated to an unwarranted position of importance by the truly geeky.

Hold on there, Eric! Are you calling us "truly geeky?" As opposed to false geeks? Does Lance ride with a calculator on his bike? Does this count as illegal performance enhancing equipment? Do the French know about this?

Are you calling us "truly geeky?"

If the propeller beanie fits...

Actually, I was referring to myself. But if you're similarly inclined to elevate boring trivialities, come on in...the water's fine!

Oh, and Lance trains (trained) with an SRM Powermeter that measures his power output at the crankset and sends the data to a handlebar mounted storage unit. The data is then downloaded at his training lab and analyzed in exquisite detail. As one article put it, Armstrong doesn't worry about speed because speed lies; power doesn't.

The French knew about it. They also knew that there was no legitimate means of defense against his physiology and training, so they had to resort to slander and libel. And, of course, that didn't work either. Pity the French.

Doesn't the distance traveled also have to do with the size of it's tires?

Bert, that's a good point that I failed to mention. Gear charts are normalized for a specific tire size, generally either 27" or 700cm, the most common size for road bikes.