Wheel size has nothing to do with the speed of a bicycle on the road. If bigger wheels were faster, don't you think you would see bigger wheels not smaller wheels on bicycles built to ride over mph?
A road bike, or tandem bike with 26 inch wheels is geared to travel at the same speed as a bike with c wheels. The answer lies in gear inches. Gear inches is a means of measuring the relative number of inches traveled forward per crank revolution.
The higher the 'gear inches' the more distance traveled per crank revolution. A road racing bicycle in its fastest gear, is usually geared to about 'gear inches'.
This is true no matter what size the wheels are. My road bicycle has 26 inch wheels, and my top gear is inches. If I have a inch gear, and I'm pedaling at a cadence of 90 revolutions per minute, I will be traveling forward at about 31 miles per hour no matter how big my wheels are Below are a few standard gearing patterns that are used for c and 26 inch road wheels.
Small wheels usually require fewer spokes to achieve the same stability as the common 26 to 28 inch wheels, and fewer spokes generate less turbulence drag than larger wheels, leading to higher speeds.
As pointed out by Alexi Grewal, Olympic road race gold medalist, a small wheel is more efficient than a large wheel in speeds up to 16 mph. In speeds between 16 and 33 mph, small and large wheels are equally efficient. Only in speeds faster than 33 mph is a large wheel preferable, Grewal says. When you're riding in downtown traffic and need to stop frequently, you will appreciate fast acceleration. Because smaller wheels weigh less, they create a lower moment of inertia.
As a result, they get up to speed quicker and climb better. Small wheels create a more maneuverable bike. Because of their size, they are more responsive to steering and they present increased tire compliance with the road surface because they get higher pressure per square inch on the ground. The superior maneuverability is particularly helpful on wet surfaces and in tight turns. When the first 29ers were debuting, even with rim brakes and 3 inches of travel it was apparent then that they were better over the bumps.
This means the vertical impulse happens slower since there is more time spent traversing up and over the bump. Larger wheels are significantly heavier and also more delicate for a given hub width due to the spoke angle.
Also, with drop bars all that tire clearance can do weird things to the frame geometry since bikes with flat bars have a much longer top tube for a given reach. The rumble strip test uses bumps that are small enough that a lot of the impulse will be absorbed by the tire. Once you start hitting bigger bumps, your tissues are going to start bottoming out against themselves more. They mostly occur when the bike vibrates, even on smooth roads. The rumble strips caused intense vibrations that the tires could not absorb.
That is why the power output at the same speed was 70 Watts higher on the rumble strips, even with 38 mm tires. After riding 25 kilometers 15 miles on the rumble strips during the course of a single morning to test various setups, my whole body tingled. If you have a closer look related to MTB you will find different reasons. For example, you mentioned CC races. To win a WC race it is important to be able to set apart especially in the downhills from your chaser before the finish line.
One step is to slackened the head angle from 71 to 69,5 to get a more stable, confident and faster bike. With the bigger wheels you will have a better center of gravity related to the wheel axle with similar results.
Bottom line, you can go a little bit faster through rough terrain. This is kind of what I was thinking. Mountain biking today is not like it was 20 years ago. The winning moves in mountain bike races are usually on the downhills on a course built for bikes. Bombing down purpose built mountain bike trails, I think that the new wheel size and geometry really are dialed for that style of riding.
For the more traditional style of mountain biking: say you are going a long distance on a trail not purpose built for bikes and spending as much time going uphill as downhill, and say you rode to the trailhead instead of driving there…. I think 26 inch wheels are still the best for this application. To put it another way, if I wanted the best possible bike for an XC or downhill mountain bike race, I would absolutely go with a modern mountain bike. Thank you again for honest scientific information.
Thanks, MTB. They also are great for bikes with smaller frames, where larger wheels cause fit and toe overlap issues. Understanding the relationship between wheel size and gearing can help us make smarter choices on the road. More: 3 Steps to a Faster Bike Split. Let's first get a handle on the real size difference.
What do c and c translate to in terms of on-the-road distance? Assuming we use a standard 23mm tire on both wheels, the circumference distance around the outside of the wheel of a c wheel is For a c wheel, it's We're going to knock off the decimal place for the rest of this discussion to simplify. This means that for each full revolution, the c wheel goes 16 centimeters farther than the c.
Doesn't sound like a lot, right? Well, extrapolate that out to a mile ride. So, that c wheel has to turn 6, more times to cover the same century ride.
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