I just did the Courage Classic bike ride for The Children’s Hospital in Denver with a friend (120 miles, 7000 ft of climbing day one; 100 miles, 7000 ft of climbing day two; 45 miles, 3500 ft of climbing day three). On the way back home we were discussing the inefficiencies of road bikes. He claimed that it basically broke down like this:
70% is in aerodynamics
30% is in rolling friction with your tires
Components such as hubs and your entire drive train take up remarkable little energy, even when squeaking and not correctly lubed
This was based upon me averaging about 18-16 mph on this ride, about 22-23 in flat areas
Does any one have anything to back this up?
Assuming that this is all basically true, how do I deal with each of these inefficiencies?
How much aerodynamic inefficiency is in the bike? How much is in my bike. Should I shave my legs? Should I buy a carbon seat post? Oval aluminum tubing? What will an aero-bar take out?
What about my tires? How much more efficient are 700 C’s vs. 650’s? I ride $15 Michelin Axial Bi-Sports with treads. How much efficiency can I add with a carbon rubber Michelin Hi-Lite Prestige’s at $40?
If components really are more inefficient than he suggests, will Dura-Ace be more efficient than Sora? Than 105’s?
P.S. How often do I have to replace a chain? Every 1000 miles seems excessive. I have put 600 on so far this month.
The Analytic Cycling web page has a lot of information on this topic, and even allows you to input various parameters and calculate the various forces on the rider. With the default settings, at 10mph the wind resistance accounts for 76% and rolling resistance for 15%. At 30mph the wind resistance jumps to 87%. The web site allows you to do the calculation with various tire sizes, etc.
The most advantage comes from reducing frontal area. The bikes with the smallest frontal areas are lowracers such as the M5 Lowracer or the Optima Baron. A fully faired vehicle such as the Flevobike Limit or the Quest have even smaller wind resistance. Unfortunately, lowracers and faired vehicles are not allowed in most road bike races, partly because of “unfair advantage” and partly because their low height and different speed profile make them unsafe to ride in a peleton (group). USCF time trials do allow lowracers, and the Lightning U-2 is specifically designed (well, modified) to comply with USCF regulations.
Actually, nobody has achieved 100mph on a flat road, with or without a fairing. The Speed101 page has information and photos of record-braking HPVs (human powered vehicles). As you can see there, the current record is 72.74 mph set by Sam Whittingham of Canada last year.
This record, by the way, will almost certainly be surpassed this fall. The 2001 World Human Powered Speed Challenge will be held in Battle Mountain, Nevada starting October 1. Besides established racers such as Matt Weaver, Olympic gold medalist Jason Queally is teaming up with some high-tech companies to challenge this record. Here is a good Times article about Jason Queally’s record attempt.
“Air resistance.
Drag from the air isn’t a big problem at low speeds. However, it has one unsavory characteristic: the force required to overcome air drag rises as the square of the speed. As we saw before, power is force times speed, so the power rises as the CUBE of the speed. In other words, to ride at 20 mph takes eight times as much power as to ride at 10 mph. To ride at 30 mph takes 64 times as much energy as 10 mph.”
But I suppose it depends on how you set up the rules. Looks like he didn’t use a fairing, but another aerodynamic trick entirely. This is cheating, isn’t it? I dunno, he gets extra guts points for trying this, if you ask me…
Oh, good point, ChasE. But do I consider that cheating. The car is doing all the work to overcome the wind resistance. The bike merely pulled along by the air pocket created behind the car.
About that motor paced bike, one thing I’ve long wondered is how he gets the thing started. Notice that it has a double reduction gear and doesn’t have any deraileurs. Based on how difficult it is to pedal from a standstill on my bike when it’s in the top gear, I imagine that thing is impossible to pedal when completely stopped.
Note the horizontal bar hanging about 3 feet behind the pace car, right about the height where the cyclist can grab ahold of it. Looks like they tow him up to speed. Boy, I’d hate to screw up trying to let go at 100+ mph. One slip and you’re a red stain on the salt flats.
Oh, BTW, I did manage to find a website by the company that made the bike, it shows a guy riding it around a parking lot at a claimed speed of 2mph. He said it was really hard to push the pedals. Alas I didn’t note the page, but I’m sure you can Google it.
Looks like you got the 100mph question answered. For the other questions:
Shaving your legs is will not cut down on air restiance. Bikers shave their legs for 2 reasons that I know of, bike grease a dirt washes off easier, and it is better for the massuse when giving a rub down after the race.
Aero bars and lighter seat post will be a little better, but the saying goes it is not the frame that will make you go faster it is the engine.
Better tires can be inflated to a higher psi. It can give you a rougher ride but a faster one.
Higher end components will give you a better ride, easier shifting, better gear ratios, and better over all quality-nuff said
With your chain, each chain has a different wear. check to see if you can see any space between the chain and the chain ring. If you can see any space you might want another chain. Hint buy 2 chains, after 6 months switch chains. the wear on the chain and drive train should be negligible.
Really? I always heard it was because when you took a dive and got a good case of road rash, the scabs on your legs healed quicker if you didn’t have hair.
to Chas.E:
Yeah I forgot about that one, but other athletes do shave their legs (swimmers, runners, etc) and they don’t get road rash. so now we have 3 reasons.
I couldn’t find the page, unless you are referring to http://www.canosoarus.com/08LSRbicycle/LSR%20Bike02.htm which has someone riding at 2 mph on previous record setting bike (the one with the oversized front sprocket). I did find the page of Hujsak Custom Bicycles who made the frame, but they don’t have anything special about the 152 mph bike.
I don’t think that horizontal bar was for towing. Instead it seems to match height with a vertical bar on the bike. Somewhere I read that there was a feedback mechanism between bike and car so that when the bike speeded up, the car did too and at the same rate. These bars are probably it.
Yeah, that’s the one I was thinking of. Nothing earthshaking, just confirmation that the bike is almost impossible to pedal unless it’s up to speed. It’s interesting that the bike is not freewheeling. Boy, there’s no margin for error on that bike, it’s like it’s a part of your skeleton.
Briminator, yeah, runners and swimmers do get road rash occasionally. Runners sometimes take a fall, and swimmers often scrape on the sides of the pools. My sister was a swimmer and she seemed to always have scrapes on her legs. But I’m not sure this is the reason why they shave. For that matter, I never heard of runners shaving, but hell, what do I know?
Track bikes also have the “no coasting” setup. Originally intended for indoor races on tracks, these are often used by bike messengers. I’ve read that the method of stopping them involves lifting the rear wheel and stopping pedalling. This is obviously rather harsh on the knees. From what I understand, about half of all bike messengers use track bikes.
Another way to reach 100 mph on a bike would be to ride it out the back of an airplane.
As for the question in the OP about the relative proportions of rolling resistance and drag in slowing a bike down, I’ll add that drag increases proportionally with the square of the speed, while I would imagine (taking a somewhat educated guess) that rolling resistance only increases proportionally with the speed.
And I’ll toss in a tip from Bicycling magazine about achieving your highest max speed, which is to get an aero bar. That’s one of those things that puts your elbows on top of the handlebars and your hands out in front. If you do install one, you will need to move your seat forward and tilt it down in front.
Rolling resistance is roughtly constant, regardless of speed. The power to overcome rolling resistance is proportional to speed, because you are moving more distance per unit time while pushing against the same resistive force. (If that sounds confusing, compare running up the stairs vs. walking up - you are exerting the same force, i.e. your body weight, but it takes more power to move faster.) And as absoul posted, air drag is proportional to the square of speed, and power to overcome it is proportional to cube of the speed.
