Buying A Bicycle: What Size Wheels Do I Need?

What to know for selecting your bike, gears, tires and other equipment. Consumer Tips for choosing bicycles.

In selecting the wheel size when buying a bicycle, you need to ask yourself this question. What type of riding would I like to do? Do you see yourself as a racer, riding at a fast pace, climbing mountains and going long distances, then you need a large wheel. The standard in today's road bike is seven hundred millimeters in diameter. Maybe you picture yourself riding dirt trails in the backcountry or a casual ride on a bike path at the beach or other recreational area. You want a lower to the ground wheel, a twenty-six inch diameter wheel that comes with most off-road bikes.

What about touring on back roads in a relaxed position such as a recumbent might offer. They can have wheels that are sixteen or eighteen inches in diameter. Whatever style riding you like or whatever size wheel your bike would come with, it's knowing the inches your wheel can cover in one revolution of the pedal stroke that's important.

What does that mean, the inches your bike can cover in one pedal revolution""remember seeing pictures or perhaps, at a parade, a strange looking bicycle that had a very large wheel in front and a smaller wheel in back. A person sat at the top of the large wheel while they pedaled. That bike is called an "╦ťOrdinary'. The bikes of today are in a general category called "╦ťRegular or Modern'.

It is the wheel sizes from the Ordinary that we developed the system of gear inches for today's bikes. Back then; at the turn of the last century, when Ordinary bikes were what everyone wanted, you would have several front wheels in various sizes. If you planned on riding down a hill or on a flat surface, you would want a big wheel. If you planned to climb a hill, you would want to put on a small wheel.

Why? The bigger the wheel, the faster you go and the harder it is to turn the wheel. The smaller the wheel the slower you go, making it easier to push the pedal with one revolution of your leg. In other words, if you marked the beginning of where you started and then, after one complete revolution of your pedal, marked the end, that would tell you how far you went in one complete leg stroke. Makes sense doesn't it. A small wheel, you go a short distance, but it's easier. A large wheel and you go a further distance but it's harder to push because you are covering more ground.

Modern bikes have gears to change the inches a wheel can cover in one pedal stroke, the rider no longer need switch wheels, they simply switch gears. That means you need to know the formula to convert gears into inches. Take the amount of teeth in the chain ring (that's the gears where the pedals are attached) divided by the amount of teeth on the rear cog (that's the gear or gears on the rear tire). Multiply that by the wheel diameter and you have the inches.

So lets say you have a 53 teeth chain ring in the front and one of the rear cogs has 17 teeth. Divide 53 by 17 then multiply by 27 (the usual diameter of a road bike wheel, a mountain bike would be 26). The total rounded off would be 84.2 inches. You would cover in one revolution of the pedal, a little over eighty-four inches. With this simple formula, you can determine what size wheel you are riding. This is important because you can tell what combination of gears will give you the most options.

You want gears on your bike that give you the maximum amount of different inches the wheel can cover in one pedal stroke without duplicating the combinations. In other words, you could have a bike with twenty possible gears""two on the front, ten on the rear cog set and have only twelve actual different sizes. Depending on the gear's ratio and the diameter of your wheel, you can end up with the same amount of inches. For instance: You're riding your bike and you switch to the big chain ring in front. It's now hard to push the pedal, so you shift the rear de-railer to a larger toothed gear, making it easier, but you're not going any faster or slower. That's because you are covering the same distance in one pedal stroke as you were before shifting.

For general knowledge of wheel size, first decide what type of riding you would like to do. The smaller the wheel the closer to the ground and more stable you are. The larger the wheel the faster you will go and the higher up you'll sit. The size of the wheel can always change by switching the gears.

© High Speed Ventures 2011