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Comment by mrob | Hacker News Reader

>2% is nothing to sniff at in cycling (people pay thousands of dollars for that kind of advantage)

2% is nothing to sniff at only if you're hampered by the arbitrary UCI rules. By far the biggest factor in cycling performance is air resistance, and the obvious solution (fairings) is banned. The UCI has been disastrous for bicycle technology. Most high-end buyers like to pretend they could compete professionally one day, so they abide by the same rules, which means there's no incentive to develop truly fast bikes.

The UCI rules should allow any safe design, and avoid giving an advantage to richer teams by setting a price limit (bicycles are already required to be commercially available).

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Fairings aren't as useful as you might think in most circumstances. On an upright bike, they need to be enormous to offer an appreciable benefit, which makes them heavy and difficult to control in crosswinds.

The optimum solution is a recumbent bike - by going feet-first, you can reduce your frontal area by more than 50%. With a much smaller frontal area and a much lower center of gravity, a tail fairing becomes a practical proposition.

Fully enclosed recumbents can achieve phenomenal results in the right conditions (Sam Whittingham's 91km hour record, Andy Wilkinson's 41 hour LEJoG), but they immediately become a handicap with any sort of gradient because of the ~20kg weight penalty and they're unbearably hot.

> The optimum solution is a recumbent bike

Recumbents are cool and much faster in some situations but pro cycling exists mainly to sell stuff and upright bikes look cooler.

Recumbents have been banned by the UCI since 1934, so that ship has sailed. If we had seen recumbents on the Tour de France for the last eighty years, they'd probably look cool and upright bicycles would look weirdly old-fashioned.

There is also the point that you don't want to ride a recumbent bike on a road with traffic.

Ok flat ground or a descent a recumbent may be faster (my experience is that most recumbents can’t keep 22-25mph on flat ground) but it won’t be faster climbing hills and they have a longer wheelbase and are quite a bit less maneuverable. On hill climbs the weight is the most obvious factor but I’d be surprised if you can generate the same amount of power in the supine position as you could in the standing position.

Since most bicycle racing is dominated by climbing hills, I don’t think anyone would ride a recumbent even if it was legal.

A modern short wheel base recumbent has a similar wheelbase to a conventional 700c road bike. The hill climbing issue is still the subject of some debate; your peak torque is undoubtedly lower (because you can't put your full weight on the pedals) but there's no obvious biomechanical reason for lower power.

Any advantage an upright bike might have in the mountains is completely neutralised by the tremendous aerodynamic advantage of a recumbent. A good lowracer recumbent with a tailbox has about half the drag of a normal racing bike. Worse still, an upright rider gets almost no benefit from drafting a recumbent rider.

If the UCI legalised recumbents, a team using upright bikes wouldn't even finish the first stage of a grand tour within the time cut-off. Any team using recumbents could disappear off the front of the peloton and would be impossible to catch. In a time trial, there's simply no contest - the recumbent riders could demolish the upright riders without breaking a sweat. To neutralise that advantage, races would need to be organised exclusively in the high mountains with no appreciable amount of flat roads.

Try making a bunny hop over a pothole on a recumbent. Upright bikes are far more versatile, just imagine recumbent cyclocross.

Why? Is there some physiological factor? Blood flowing too much to the head? Allegedly the hydrostatic pressure is lower, breathing is easier due to lack of bending on a recumbent bike, so it should help endurance, as long as the bikes are the same weight.

    > The optimum solution is a recumbent bike...

On a flat individual time trial, sure.

But pro races are really all about bursts of acceleration as well as topography. Recumbents just wouldn't cut it.

Old guys going fast in a straight line by themselves in an egg-shaped container just isn't interesting to watch.

    > ...which means there's no incentive to develop truly fast bikes.

UCI compliant bikes are "fast enough" for the sport and have many practical considerations in addition to normalizing design features.

It really is mostly about the training, the athletes and the teams.

In cycling, performance is result of the combination of many factors of which equipment is but one.

I agree that the UCI has been bad for progress. That being said, I raced in college (at the collegiate level, not professionally) and saw plenty of people using UCI-noncompliant bikes.

Historically, the UCI did use "safe design" as the metric -- they used it to exclude Graeme Obree, whose bicycle-cum-dishwashing-machine was probably safe enough for him to be riding on a closed track. That's not to say that the UCI should block innovative designs, just to note that they'll use any regulation supplied to restrict cyclists/companies/countries that end up on their naughty list.

Do you think there's a market for super-efficient commuter bikes? Or is air resistance no longer the limiting factor at commuter-bike speeds and weights?

I think there's a limited market for them, because the value of aerodynamics depends heavily on how you ride.

Wind resistance increases with the square of the speed. Pros can ride at 30mph average on fast stages, where managing wind resistance is huge. A typical road bike commuter might average 15mph. All else being equal that's 1/4th the wind resistance (1/8th the power needed to overcome it), which is still big, but not the overwhelmingly important concern it is for the pros. A commuter on a utility bike who doesn't want to sweat might average only 10mph, so 1/9th the wind resistance (1/27th the power needed to overcome it). At that speed it doesn't feel so important.

For the pro, speed is the top priority, but the commuter also has to consider comfort, reliability, and visibility of other traffic (recumbents put your head lower down so it's harder for you to see over cars, and it's harder for them to see you). On heavily congested roads, e.g. central London, traffic might prevent you from going fast enough for wind resistance to be a major concern. If you commute over steep hills then reduced weight might benefit you more. But if you have a long and flat commute with light traffic, I think a super-efficient commuter bike would be valuable, and it's a pity that UCI rules discourage development of super-efficient bike technology.

EDIT: added power values as per HankB99's comment.

>Wind resistance increases with the square of the speed. To be pedantic, wind resistance varies with the cube of the speed. That's my recollection and seems to be used in the formula used to calculate power required at https://www.exploratorium.edu/cycling/aerodynamics1.html.

Drag force does vary with the square of the speed, but power needed to overcome that drag force varies with the cube of the speed. From Wikipedia[0]:

"Note that the power needed to push an object through a fluid increases as the cube of the velocity. A car cruising on a highway at 50 mph (80 km/h) may require only 10 horsepower (7.5 kW) to overcome aerodynamic drag, but that same car at 100 mph (160 km/h) requires 80 hp (60 kW).[16] With a doubling of speed the drag (force) quadruples per the formula. Exerting 4 times the force over a fixed distance produces 4 times as much work. At twice the speed the work (resulting in displacement over a fixed distance) is done twice as fast. Since power is the rate of doing work, 4 times the work done in half the time requires 8 times the power."

Power output is directly felt by the rider, so it's the more relevant comparison here, and your comment is more practically useful.

[0] https://en.wikipedia.org/wiki/Drag_(physics)#Power

Oh... right. Work done is force * distance so distance varies linearly with speed.

This is the kind of reasoning I was looking for. Thank you!

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