Recumbent - How much faster are u on a 'bent that a std road bike?

Wow, there really are a lot of misconceptions and pre-conceptions about recumbents. [...] If you really want to test the speed differences between different bikes, the only way to do that is to put the same pilot on each one, use a calibrated electric motor for the motive power and have a go. This way, we are not measuring the human/machine combination but the vehicle by itself.
Wow, there really are a lot of misconceptions and pre-conceptions about measuring vehicle drag.

Wow, there really are a lot of misconceptions and pre-conceptions about recumbents. While full fairings do present an extra load on the rider during acceleration, they also offer an inertial advantage on slight inclines and a major aerodynamic advantage in most wind situations. While it is not possible to sprint in the same way that an unfaired bike can sprint, for all-out speedbikes, the limiting factor in acceleration is the transmission which itself must be limited to only a few ratios to keep vehicle width to a minimum.

For example, here are Sam Whittingham's lap times for the 1-hour record he set this summer at the Ford 5-mile oval. Note that the final distance ridden was about 90.6 km over the hour.

Lap 1, 74.70 kph
Lap 2, 91.02 kph
Lap 3, 91.99 kph
Lap 4, 92.15 kph
Lap 5, 92.21 kph
Lap 6, 92.09 kph
Lap 7, 91.74 kph
Lap 8, 93.02 kph
Lap 9, 93.13 kph
Lap 10, 93.03 kph
Lap 11, 94.38 kph

Since it was spent accelerating from zero, it's clear that with an average of 80% of his target speed, he is likely very near his record average by the end of that first lap. Under full acceleration he brought that same machine to over 133 kph within the 5-mile run of the Battle Mountain speed course.

If you really want to test the speed differences between different bikes, the only way to do that is to put the same pilot on each one, use a calibrated electric motor for the motive power and have a go. This way, we are not measuring the human/machine combination but the vehicle by itself.

Barring aerodynamic aids is not about speed but athleticism. The UCI has clearly given the message that their sport is about the athlete and not the technology, never mind that aerospace technology is required to be competitive. I'm quite sure that lighter and more aerodynamic bikes magnifies the difference between riders so limits on the technology serve to level the playing field, with the clear effect that UCI racing is much more exciting from a competition perspective.

Unlike the UCI (or the USCF for that matter), recumbent racing is clearly about the absolute performance capabilities of the human/machine combination.

Interesting you mentioned RAAM, since the recumbent teams are not only beginning to place, but win. IIRC, last year, John Schlitter rode a Bacchetta to first place in his 50-plus category and this year, Rans took the 4-man team honors. And never mind that Lightning and Easy Racers fielded streamliners against each other some years ago, with Lightning setting some crazy fast record for the crossing. From what I heard, the inside scoop was that Easy Racers dropped out about halfway because the downhill speeds getting so dangerously fast, the support vehicles couldn't keep up... something like 85-90 mph.

:)ensen.

What's the misconception? Running laps or a straight run-up is a farce which distorts the important aspects of true vehicular speed. Let's not forget that the whole point of a vehicle is to actually go somewhere. If this were not the case then we could just shoot human powered arrows leaving the human power source at the start line. For true vehicular speed acceleration is much more important. That's why fairings aren't as fast as the records seem to indicate because the test doesn't measure what it should.

Also correct me if I'm wrong, but do recumbents actually hold any general RAAM records at all? The records page isn't entirely clear, but it appears that except for the 4-man team every record is held by an upright:
http://www.raceacrossamerica.org/raam/raam2.php?N_webcat_id=51

Not trying to be combative, please point out my misconceptions.

See how the trolls have pulled the thread off course, from "How much faster are u on a 'bent than a std road bike?" to demanding race results. You guys and girls who want proof, you'll just have to come on a ride with me or come up with some money to commission some serious research. We don't do that here; we just ride.


Every bent I see on the road I'm passing. And I'm a girl. All the riders are old, however. This is why they are so slow I think. Have never seen a fit 25-year-old on a bent. That would be a better test.

This is for you Laurel. I'm on the yellow lowracer. I'm not going to state any speeds that you'll disbelieve anyway, but you can tell it's more than 12 mph. You can also tell that the Safety Bike riders, while not racing, were not unexperienced, and were doing a 'healthy' pace. But you can also see I wasn't pushing myself much, either. This was taken less than halfway into a century, so they got the standard pass rather than the full Top Gun fly-by(tm). After all, we must pace ourselves, right? :innocent: My buddy hung 'way back to get a better view. (There's nothing to see after he catches back up, just me loafing along.) IIRC that was my 51st birthday ride and we finished the century in 4:40 or thereabouts. Apologies for the crooked helmet cam. Does it prove that recumbents are the fastest things on the road? Nope, just that this 50+ can make it go down the road at a respectable speed. And of course, by my account, it's faster than I used to be on a Safety Bike. If you don't believe 17%, then make up a figure of your own. Whatever makes you feel good about yourself.

http://www.youtube.com/watch?v=WJKBdjOdEy4

See how the trolls have pulled the thread off course, from "How much faster are u on a 'bent than a std road bike?" to demanding race results.
I don't believe I've been asking for race results. I've been asking for differences in measured drag (both rolling and aero) so we can evaluate how much of any putative speed gain is due to the bike and/or the rider. Here's the thing: when I re-started riding after a long hiatus I climbed a local hill in 19:30. Now, a dozen years older, I climb that same hill in 12:30. That's a 36% improvement. In the intervening years I've changed bikes twice. I give the bike a little credit, but not 36% worth. So saying something like "I'm 17% faster on my new bike" isn't as informative as you may think it is.

I don't believe I've been asking for race results. I've been asking for differences in measured drag (both rolling and aero) so we can evaluate how much of any putative speed gain is due to the bike and/or the rider. Here's the thing: when I re-started riding after a long hiatus I climbed a local hill in 19:30. Now, a dozen years older, I climb that same hill in 12:30. That's a 36% improvement. In the intervening years I've changed bikes twice. I give the bike a little credit, but not 36% worth. So saying something like "I'm 17% faster on my new bike" isn't as informative as you may think it is.

There are some published wind tunnel tests, here are the results from one that you can read about here (http://www.mueller-hp.com/windtunnel.htm). The Vision VR40 has a 20" front wheel, it's similar to bikes like the V-Rex and Bacchetta Giro 20. The VR65 bike with dual 24" wheels is a predecessor of the contemporary highracers, here's the best pic I could find:

http://img.epinions.com/images/opti/d9/e7/2002_Vision_R65-bikes-resized200.jpg

The upright bike is a CAAD3. And here's the drag for each bike.
http://www.mueller-hp.com/windtunnel/image002.gif
and normalized to the road bike:
http://www.mueller-hp.com/windtunnel/image004.gif

Contemporary highracers typically use the superman postion for arms for lower drag and have seats that support a much greater recline angle for better aerodynamics, and use 650c or 700c wheels for reduced rolling resistance compared with the Vision, so these numbers would be improved to some degree with the better 'bents for sale today. Blazing Pedals' exotic lowracers would rate even better still due to the reduced frontal area.

I'm sure that's all true, but the lowracer pics you posted above look to have very wide Q and the knees in particular are very far apart. Just sayin...

Actually, looks more like wide angle lens distortion vs the flattening effect of a telephoto. I mean, really, when was the last time Lake made shoes for the NBA?



Wow, there really are a lot of misconceptions and pre-conceptions about measuring vehicle drag.

Well... if we've decided to play it snippy, then maybe I should point out that it appears you are only in any of these threads to promote your Chung Method for measuring drag using a power meter on a course loop. Really though, as you might remember from other threads, I haven't needed to measure drag yet, and probably won't be needing to in the near future. Now, the before/after conditions, those are important to me. Besides, the question was about measuring speed, which must be done in the real world with varying conditions. The only thing that can be controlled is the course, which may or may not be flat or straight. While a fast machine will have a different top speed from one run to the next, a slower run does not make it less speedy.


What's the misconception? Running laps or a straight run-up is a farce which distorts the important aspects of true vehicular speed. Let's not forget that the whole point of a vehicle is to actually go somewhere. If this were not the case then we could just shoot human powered arrows leaving the human power source at the start line. For true vehicular speed acceleration is much more important. That's why fairings aren't as fast as the records seem to indicate because the test doesn't measure what it should.

Also correct me if I'm wrong, but do recumbents actually hold any general RAAM records at all? The records page isn't entirely clear, but it appears that except for the 4-man team every record is held by an upright:
http://www.raceacrossamerica.org/raam/raam2.php?N_webcat_id=51

Not trying to be combative, please point out my misconceptions.

Top speed does not need qualification. The Bullet Train goes 300 kph. Nobody ever adds: "But it took 10 miles to get up to speed." Now, while the initial acceleration to speed affects the average speed over a course, it's pretty clear that it matters relatively little. In the case of that 1-hour record I showed, the final average was only a couple KPH below the typical lap speed after the first lap. Acceleration, and thus vehicle weight matters even less at the the TdF TT since the start gate has a big ramp that puts in most of the initial acceleration.

As for RAAM, it's true they keep records, but the only ones that matter are the average speed since the course length changes from race to race. I haven't looked on their site for a few months, but I seem to recall that they had one record crossing that was qualified with a note that it was also the shortest course length. The recumbent riders are beginning to show success... is that not enough?



I don't believe I've been asking for race results. I've been asking for differences in measured drag (both rolling and aero) so we can evaluate how much of any putative speed gain is due to the bike and/or the rider. Here's the thing: when I re-started riding after a long hiatus I climbed a local hill in 19:30. Now, a dozen years older, I climb that same hill in 12:30. That's a 36% improvement. In the intervening years I've changed bikes twice. I give the bike a little credit, but not 36% worth. So saying something like "I'm 17% faster on my new bike" isn't as informative as you may think it is.

Just because you saw an increase in your physical ability does not negate my improvements, especially when my fitness has been steadily decreasing since switching from DF to recumbents.


:)ensen.

There are some published wind tunnel tests, here are the results from one that you can read about here (http://www.mueller-hp.com/windtunnel.htm).
Thanks very much--I'd seen that before but I'd forgotten about it so I'm glad you linked to it. It is consistent with what I wrote several posts above: with the possible exception of low racers (for which I haven't yet seen any data) most unfaired recumbents appear to have aero drag no better than a well-positioned rider on a modern TT bike.

Well... if we've decided to play it snippy
Wait a sec. Anyone who scrolls upthread will see that I used exactly your own phrasing. Did you think it snippy then, or only now?


maybe I should point out that it appears you are only in any of these threads to promote your [method].

I haven't mentioned any particular method in this thread, though I did make the generic observation that there are several methods to measure drag. Strange way to promote something -- unless, of course, I wasn't promoting anything in which case it's not strange at all that I didn't mention it. You claimed "the only way to do that is to put the same pilot on each one, use a calibrated electric motor for the motive power and have a go." This is what I dispute.


Just because you saw an increase in your physical ability does not negate my improvements, especially when my fitness has been steadily decreasing since switching from DF to recumbents.

My intention was never to negate your improvements. My intention has always been to understand how much of an improvement is due to the bike and how much due to the rider. Perhaps your fitness has not decreased as much as you think, or even at all -- or maybe you've actually improved. How would you know without measuring?

Thanks very much--I'd seen that before but I'd forgotten about it so I'm glad you linked to it. It is consistent with what I wrote several posts above: with the possible exception of low racers (for which I haven't yet seen any data) most unfaired recumbents appear to have aero drag no better than a well-positioned rider on a modern TT bike.

The recumbent equivalent of a well positioned rider on a modern TT bike IS a lowracer. I would compare my Stratus to someone riding a hybrid.

T... most unfaired recumbents appear to have aero drag no better than a well-positioned rider on a modern TT bike.

I'd agree with that statement; in fact I wrote earlier that most recumbents aren't faster than a road bike. I'm not sure how a TT bike crept in there, except for the troll value. I'm not aware of any recumbent rider who used to ride exclusively on TT bikes.

play it snippy

A certain conclusion that can be drawn from this thread:

Bent riders are 17% more likely to argue or defend their speed and comfort claims. I include myself in this generalization.

Gotta love it. Blazing Pedals lays down the challenge, and all the upright girls and boys ignore it and go on cherry-picking data.

How 'bout it, Laurel? You girl enough to go for a ride with Blazing Pedals? Better yet, try and keep up with John Schlitter for a mountain or two...oh, that's right. He doesn't fit into your data set, does he?

try and keep up with John Schlitter

Another ridiculous argument. Nobody is challenging the ability of John Schlitter.

The original question posed was "are you faster on a bent?"

Some think they are 20% faster. But only in the flats.

Does that mean John Schlitter would be 20% SLOWER on his last race upon Lance's latest Madone? Does this mean a rider of his caliber would now ADD 20 hours to a previous run of 100 hours just by going uright?

I don't think so.

I don't think so.

Right, pal. And who are you? Just some schmoe on the internet.

Here's my answer to the question, "Are you faster on a bent?"

Yes I am. I am 15% faster on my bent than I am on my upright.

I will give you $1,000 if you can prove me wrong.

Top speed does not need qualification. The Bullet Train goes 300 kph. Nobody ever adds: "But it took 10 miles to get up to speed." Now, while the initial acceleration to speed affects the average speed over a course, it's pretty clear that it matters relatively little. In the case of that 1-hour record I showed, the final average was only a couple KPH below the typical lap speed after the first lap. Acceleration, and thus vehicle weight matters even less at the the TdF TT since the start gate has a big ramp that puts in most of the initial acceleration.

As for RAAM, it's true they keep records, but the only ones that matter are the average speed since the course length changes from race to race. I haven't looked on their site for a few months, but I seem to recall that they had one record crossing that was qualified with a note that it was also the shortest course length. The recumbent riders are beginning to show success... is that not enough?

I don't think anyone is denying that recumbents reach higher top speeds (I think even slow riders on slow recumbents experience this), but top speed is a completely useless achievement. I also agree the acceleration matters relatively little to the courses and tasks set out for records, but that's neither here nor there.

The issue is simply this: acceleration is almost as fundamental as course length to the time of vehicular travel and the only reason "speed" is even relevant is as a direct proxy for travel time which is a valuable asset in the real world. Therefore, courses and tasks devised to purposely eliminate acceleration are akin to making a race shorter to make the times faster; It undermines the entire point of having the race or trial in the first place and devolves the entire effort into a mere game completely disconnected from everything of importance or value. Maybe that doesn't bother you, but if it doesn't bother you then why should you care about recumbent bicycles at all? After all, if we're just playing games with rules chosen regardless of real world importance or value then what's wrong with the upright bicycling game specified by the UCI? It's as good of a penis measuring contest as any other and isn't that what games are for?

IMHO the only reason to consider recumbent bicycles is with regards to their capability as human powered vehicles and if even with tests heavily heavily biased in their favor (tests which measure only top speed, tests which minimize the importance of acceleration, etc) they just barely have an edge (as evidenced by the controversy of this thread) then I find it unlikely that they could have much of a true advantage in this role especially since with respect to the few relatively unbiased tests of vehicular speed out there (such as RAAM) they've failed to accomplish anything more than just barely staving off complete domination by the uprights. So no it's not enough.


I'm not aware of any recumbent rider who used to ride exclusively on TT bikes.

+1 That's why I ride a recumbent. Of all the bikes which have been able to best the standard UCI hour record (ie with best human effort or IHPVA), the only ones I'd be willing to ride are recumbents and I don't know of any other cyclists who ride TT bikes as vehicles.

Record times by elite athletes are interesting, but here's the real-world comparison I'm pondering:

My last workplace was 15 miles away, in mostly flat suburban sprawl, moderately frequent stop signs, and traffic lights every mile or so. I used my DF bike (Specialized Allez Elite Triple, Ultegra 3x9) with full commuting kit (lights and fenders and panniers) riding with my hands on the brake hoods. I cruised around 20-23 mph, and I got to work in around 50 minutes. That (doubled, plus showers) was about the outer limit of the amount of time I could devote every day to traveling.

On Monday I started a new job that's 22 miles away in roughly the same direction. Some of the route choices (my favorite expressways (http://en.wikipedia.org/wiki/Santa_Clara_County_Expressway_System)) provide extended distances between stops, often several miles if the light timing works out. For the purpose of decreasing my trip time, I'm pondering a Volae or Bacchetta or similar highracer (105 or Ultegra level components, dual 650s) with a tailbox or aero panniers, and perhaps a full windshield. Availability of a windshield would affect my choice of bicycle. (suggestions are welcome)

Might I reasonably expect the highracer's aero advantage to bring my new 22 mile trip time into rough parity with my DF's old 15 mile trip time?

Might I reasonably expect the highracer's aero advantage to bring my new 22 mile trip time into rough parity with my DF's old 15 mile trip time?

I'm no math wiz but I think you're expecting to be 47% more efficient on the new bent? Or the equivalent of giving an upright rider a 7 mile headstart on the same course but you'll finish at the same time?

I think its time to call Myth Busters or close the thread.

...Might I reasonably expect the highracer's aero advantage to bring my new 22 mile trip time into rough parity with my DF's old 15 mile trip time?

If you're doing 300-350 watts on a commute, which is what the calculator (http://www.noping.net/english/) says, then you're well beyond my capability. I'd show up at work a sweaty, stinky mess, and probably in no shape to work for a while. You could expect some sort of increase in speed, eventually. But not 50+% faster, and not without an acclimation period. Nobody hops on a recumbent and is immediately faster.

My last workplace was 15 miles away, in mostly flat suburban sprawl, moderately frequent stop signs, and traffic lights every mile or so. I used my DF bike (Specialized Allez Elite Triple, Ultegra 3x9) with full commuting kit (lights and fenders and panniers) riding with my hands on the brake hoods. I cruised around 20-23 mph, and I got to work in around 50 minutes. That (doubled, plus showers) was about the outer limit of the amount of time I could devote every day to traveling.


I guess this explains why I'm so "slow" compared to other forum members. If 15 miles in 50 minutes is "cruising at 20mph" then I guess I "cruise at 30mph". :roflmao2:


If you're doing 300-350 watts on a commute, which is what the calculator (http://www.noping.net/english/) says, then you're well beyond my capability. I'd show up at work a sweaty, stinky mess, and probably in no shape to work for a while. You could expect some sort of increase in speed, eventually. But not 50+% faster, and not without an acclimation period. Nobody hops on a recumbent and is immediately faster.

He said he rides the DF on the hoods (not even in the drops) whereas on a highracer he can ride the whole way in the rough equivalent of a TT position, not to mention the fact that the tailbox will be more aero than his current luggage solution (especially panniers) and he can ditch the fenders (superfluous with a highracer) which I believe are a huge drag (something your roadie calculator doesn't tell you, does it).

I think it's definitely doable, especially since he says there are fewer stops on the new route which will make the biggest difference and multiply the advantage of the highracer. Although he should definitely go with a tailbox/bag over "aero" panniers.

I used my DF bike (Specialized Allez Elite Triple, Ultegra 3x9) with full commuting kit (lights and fenders and panniers) riding with my hands on the brake hoods. [...] I'm pondering a Volae or Bacchetta or similar highracer (105 or Ultegra level components, dual 650s) with a tailbox or aero panniers, and perhaps a full windshield.

Might I reasonably expect the highracer's aero advantage to bring my new 22 mile trip time into rough parity with my DF's old 15 mile trip time?
Let's say the route was completely flat with no stops whatsoever (those assumptions will tend to tilt the advantage toward the heavier bike). A typical commuter setup like that with hands on hoods will have a CdA around 0.45 m^2, though floppy clothing or stem stack can move that up or down. Anyway, for an equivalent time on a 22 mile route, you're going to need a CdA of around .12 or .13 m^2.

Let's say the route was completely flat with no stops whatsoever (those assumptions will tend to tilt the advantage toward the heavier bike). A typical commuter setup like that with hands on hoods will have a CdA around 0.45 m^2, though floppy clothing or stem stack can move that up or down. Anyway, for an equivalent time on a 22 mile route, you're going to need a CdA of around .12 or .13 m^2.

What is the CdA penalty for fenders? Panniers? Rack trunk? "Commuter width" tires for the ass hatchet? Also surely floppy clothing will give a higher CdA on the upright due to the bigger A.

Not being facetious, just curious if you have measured a real commuter setup or if you're just talking about being on the hoods. I'm impressed with your method and posted it over in the folding bike forum where we're always arguing over the the rolling resistance/aero benfits of tire diameter, width, and pressure, particularly as it relates to forms of suspension other than pneumatic tires. Are you familiar with Alex Moulton's claim that a high pressure skinny small diameter tire with suspension has both less rolling resistance and aero drag than a conventional diameter wheel with pneumatic tire suspension?

What is the CdA penalty for fenders? Panniers? Rack trunk? "Commuter width" tires for the ass hatchet? Also surely floppy clothing will give a higher CdA on the upright due to the bigger A. Not being facetious, just curious if you have measured a real commuter setup or if you're just talking about being on the hoods.
I've measured myself on the hoods of my commuter bike which has short fenders but no panniers at 0.42 m^2, so I added a little for the panniers. However, there's inherently more variability in position on a commuter bike so that was just a ballpark estimate. A floppy jacket can make a huge difference: even on my non-commuter (i.e., with a slightly lower position than on my commuter) it added .06 m^2. The problem in my case is that I have skinny biker's arms so the sleeves flapped around a lot. Since making that estimate I switched to wearing double jerseys and double arm-warmers unless the weather gets really cold.

Are you familiar with Alex Moulton's claim that a high pressure skinny small diameter tire with suspension has both less rolling resistance and aero drag than a conventional diameter wheel with pneumatic tire suspension?
Yup. I've never tested it though. TAnhalt has done some field testing of differential pressure with 700c tires and, unlike crr tests on rollers, found an inflection point where increased pressure resulted in increased rolling drag. That overinflation point appears to differ from surface to surface.

The issue is simply this: acceleration is almost as fundamental as course length to the time of vehicular travel and the only reason "speed" is even relevant is as a direct proxy for travel time which is a valuable asset in the real world.

While the effects of acceleration are being minimized in various competitions and tests in order to test specific things, such as top speed, I think you are also attributing a far greater effect for it in cycling than it has.

For example... the 1-hour TT and two riders both of whom can sustain a top speed of 54 kph. The difference is that rider A can accelerate to speed in half the distance as B. Their rides can be broken up into two parts, the acceleration phase and the finish.

From Wikipedia (http://en.wikipedia.org/wiki/Uniform_acceleration), the acceleration phase looks like this:

Distance = (Start Speed + Final Speed) X Time / 2
Time = 2 x Distance / (Start Speed + Final Speed)

So if A can accelerate to 54 kph in 150m the ride works out as:

Acceleration:
T = 2 x 150m / (0 m/s + 15 m/s)
T = 20 secs

Finish:
59 min 40 sec to ride at 54 kph which works out to 53.7 km

Total:
53.9 km ridden in one hour.

For B accelerating at double the distance (300m) the ride works out as:

Acceleration:
T = 2 x 300m / (0 m/s + 15 m/s)
T = 40 secs

Finish:
59 min 20 sec to ride at 54 kph which works out to 53.4 km

Total:
53.6 km ridden in one hour.



I really don't think many people would call 53.6 kph vs 53.9 kph much different at all.

:)ensen.

PS: I always knew the difference was maybe 1 kph average speed, but I was curious exactly how much so I looked it up and ran some numbers. Turns out that acceleration is even less of a factor than I originally thought.

While the effects of acceleration are being minimized in various competitions and tests in order to test specific things, such as top speed, I think you are also attributing a far greater effect for it in cycling than it has.

Hmmm. I'm not sure how much effect Chucky is attributing to acceleration but I think it has a huge effect on cyclists and cycling behavior. You think all those guys running stop signs are doing it for the thrill?

If you're doing 300-350 watts on a commute, which is what the calculator (http://www.noping.net/english/) says, then you're well beyond my capability. I'd show up at work a sweaty, stinky mess, and probably in no shape to work for a while.That's why I take a shower upon arrival, and change into office clothes.


I guess this explains why I'm so "slow" compared to other forum members. If 15 miles in 50 minutes is "cruising at 20mph" then I guess I "cruise at 30mph". :roflmao2:15 miles in 50 minutes is an overall average of 18mph. My normal cruise speed on flat ground with no wind is 20 to 23 mph. The difference is all the time I lose slowing down, waiting at traffic lights, and accelerating back up to speed. A significant portion of my new route has more distance to ride at speed and fewer places to stop, so it favors the recumbent's advantages.

What is the CdA penalty for fenders? Panniers? Rack trunk? "Commuter width" tires for the ass hatchet? Also surely floppy clothing will give a higher CdA on the upright due to the bigger A. I commute on 700x25 Conti Ultra Gatorskins, at around 100psi (30+lb bike and 210lb rider). The fenders are SKS Race Blades because that's all that fits on this bike. I try to keep the panniers snugged down so they're not too bulky. I wear tight cycling clothing, except if it's raining hard enough to get out the floppy jacket, in which case it slows me down.

I commute on 700x25 Conti Ultra Gatorskins, at around 100psi (30+lb bike and 210lb rider). The fenders are SKS Race Blades because that's all that fits on this bike. I try to keep the panniers snugged down so they're not too bulky. I wear tight cycling clothing, except if it's raining hard enough to get out the floppy jacket, in which case it slows me down.
In that case I think my estimate is in the right ballpark: you'd need a new bike with a CdA of around .12 or .13 m^2.

BTW, I'm also guessing your "commuting" output at around 2 W/kg (which isn't out of line for commuting).

Hmmm. I'm not sure how much effect Chucky is attributing to acceleration but I think it has a huge effect on cyclists and cycling behavior. You think all those guys running stop signs are doing it for the thrill?

"A watched pot never boils." and "Time flies when you're having fun."

Losing 10 secs at an intersection always seems longer for the person doing than the person observing. Just as with all the car drivers that speed up and pass other cars to reach the next red light, cyclists dislike stopping, especially when they have to unclip and put their foot down. I also think that the more someone likes speed, the more they will be frustrated at any delay. I hate to admit it, but I fit this stereotype, even though I know the difference over my typical commute might be only a minute or two.

:)ensen.

I think [acceleration] has a huge effect on cyclists and cycling behavior. You think all those guys running stop signs are doing it for the thrill?
Losing 10 secs at an intersection always seems longer for the person doing than the person observing. Just as with all the car drivers that speed up and pass other cars to reach the next red light, cyclists dislike stopping, especially when they have to unclip and put their foot down. I also think that the more someone likes speed, the more they will be frustrated at any delay.
That cyclists dislike losing 10 seconds doesn't explain why they're more likely to obey traffic signs once they get off the bike and into their cars. You're saying they don't like losing 10 seconds when they're on a bike but they don't mind when they're in a car? What does explain that behavior is that on a bike acceleration even to modest speeds requires a fair amount of effort. My city has a network of bicycle boulevards, ostensibly to promote cycling. Unfortunately, the city insisted on installing stop signs at almost every intersection. I did a comparison of the power required to ride both a neighborhood bike boulevard and a parallel arterial, so I have lots of data on how much power it takes to accelerate to modest, moderate, and high speeds. Even accelerating from a stop to a modest commute speed typically requires a power spike in excess of FTP. Because of that riding a bike boulevard is not only slower but it also takes more Joules of work than riding an arterial. It's really no wonder that cyclists who aren't running experiments don't stop at stop signs: the re-accelerations are substantial.

Having a way to measure speed and power can be pretty handy, eh?

That cyclists dislike losing 10 seconds doesn't explain why they're more likely to obey traffic signs once they get off the bike and into their cars. You're saying they don't like losing 10 seconds when they're on a bike but they don't mind when they're in a car?

Actually, no. I think that someone who is impatient on their bike will be impatient in their car and if I were to guess, I'd say a large majority of people don't like stopping when they are moving from A to B, including me. For instance, with good regularity, I see a number of car drivers that slowly roll through a stop sign when it is clear. The drivers have slowed enough to make a good decision on the safety of going through the intersection. If there is traffic, safety and rules requires a stop, but in the absence of traffic or pedestrians, it's fair to say that stopping is merely blind obedience. Just because there is a law and it is civilized to comply does not mean it is smart.



Having a way to measure speed and power can be pretty handy, eh?

Yes... depending on your needs. My needs don't run there yet.

In my case, being able to put a number on my energy demands does not make the effort any less painful. Since I continuously look for the flattest, straightest route with the least number of stops and intersections, it is only after optimizing my route that I might look for another way of lowering my energy requirements. And before I get into power measurement, I'd be looking optimizing the vehicle... better engine, basic fairing, disk wheels, then lighter components.

:)ensen.

That cyclists dislike losing 10 seconds doesn't explain why they're more likely to obey traffic signs once they get off the bike and into their cars. You're saying they don't like losing 10 seconds when they're on a bike but they don't mind when they're in a car?Actually, no. I think that someone who is impatient on their bike will be impatient in their car and if I were to guess, I'd say a large majority of people don't like stopping when they are moving from A to B, including me. For instance, with good regularity, I see a number of car drivers that slowly roll through a stop sign when it is clear. The drivers have slowed enough to make a good decision on the safety of going through the intersection. If there is traffic, safety and rules requires a stop, but in the absence of traffic or pedestrians, it's fair to say that stopping is merely blind obedience. Just because there is a law and it is civilized to comply does not mean it is smart.
My observations (and, as you may have guessed from my pattern in other posts, I've collected data on this) is that when crossing arterials, car drivers and cyclists don't differ in their stopping behavior but in low traffic areas (such as on these bike boulevards) they do -- and that when cyclists get behind the wheel of their cars their behavior changes. Same person, same street, same stop sign, different vehicle and different behavior. When combined with the info from the power data, the picture is clearer: top speed may be nice but cyclists are sensitive to the additional effort it takes to accelerate from a stop.


Having a way to measure speed and power can be pretty handy, eh?
Yes... depending on your needs. My needs don't run there yet.
In my case, being able to put a number on my energy demands does not make the effort any less painful. Since I continuously look for the flattest, straightest route with the least number of stops and intersections, it is only after optimizing my route that I might look for another way of lowering my energy requirements. And before I get into power measurement, I'd be looking optimizing the vehicle... better engine, basic fairing, disk wheels, then lighter components.

Fair enough. Even though I find them useful, I've never said that everyone should have a power meter. That, btw, is the reason that (despite your beliefs) I don't promote my method: not a lot of people have the equipment it takes to measure their drag (though the equipment demands are actually quite low) so it doesn't make sense to advertise it to people who can't use it. People who already have the equipment and are interested in measuring their drag eventually find it on their own anyway. When I went over to recumbents.com, I thought that dedicated enthusiasts with technical know-how would already be measuring their drag -- what I didn't understand was that in this case it appears that the availability of measuring devices drives the demand for knowing drag.

OTOH, if one is interested in how much faster a recumbent is than a standard road bike (that was the OP's original question) it seems that quantifiable estimates of drag (both aero and rolling) would be on topic.

In that case I think my estimate is in the right ballpark: you'd need a new bike with a CdA of around .12 or .13 m^2.

BTW, I'm also guessing your "commuting" output at around 2 W/kg (which isn't out of line for commuting).

So what kind of bike has a CdA of .13? Correct me if I'm wrong, but my impression is that's about the lower limit for an unfaired bike/rider.

So what kind of bike has a CdA of .13? Correct me if I'm wrong, but my impression is that's about the lower limit for an unfaired bike/rider.
Hmmm. It's not easy getting CdA measurements on recumbents and, as I've said, the few measurements I've seen don't include low racers. I've tried to make clear that I don't know anything about recumbents but do know a bit about power and measuring rolling and aero drag -- so I can say 0.13 m^2 is pretty low but I can't say for sure what bike would attain that level. Maybe a very aggressive low racer, but I'm thinking you're getting into faired territory. John Tetz has estimated the CdA of his faired Zote foam trike at 0.11 m^2. http://www.liggecykelforeningen.dk/uploads/Designseminar/vmsem6-tetz--foam-shell-velomobile.pdf

My road bike is a Specialized Sequoia, and my bent is a Bacchetta Ti Aero. I'm about 20% faster on the bent.

I have a 30 mile ride I like to do. If I ride my low racer I am 8 mph faster than my other bikes.

There are some published wind tunnel tests, here are the results from one that you can read about here (http://www.mueller-hp.com/windtunnel.htm). The Vision VR40 has a 20" front wheel, it's similar to bikes like the V-Rex and Bacchetta Giro 20. The VR65 bike with dual 24" wheels is a predecessor of the contemporary highracers, here's the best pic I could find:

http://img.epinions.com/images/opti/d9/e7/2002_Vision_R65-bikes-resized200.jpg

The upright bike is a CAAD3. And here's the drag for each bike.
http://www.mueller-hp.com/windtunnel/image002.gif
and normalized to the road bike:
http://www.mueller-hp.com/windtunnel/image004.gif

Contemporary highracers typically use the superman postion for arms for lower drag and have seats that support a much greater recline angle for better aerodynamics, and use 650c or 700c wheels for reduced rolling resistance compared with the Vision, so these numbers would be improved to some degree with the better 'bents for sale today. Blazing Pedals' exotic lowracers would rate even better still due to the reduced frontal area.

From this chart one might conclude that an upright bicycle is as aerodynamic as a recumbent which is a misleading and not particularly useful general conclusion. Maybe it's true for some recumbents since they come in some many shapes and sizes. But, I have a Bacchetta Ti-Aero (an unfaired SWB high racer) and on the rare times I ride it with my regular club I can easily outrun any upright (even hi-zoot racers with aero bars) on any downhills...And believe me many have tried to catch it. The most likely explanation for this is that the Aero has significantly lower aerodynamic drag.

One thing I have noticed is that there is some "missing" power when I ride my Aero. About 4%. Since I tend to ride uprights more frequently, perhaps it's due to lack of bent-specific conditioning.

From this chart one might conclude
There are some oddities about that chart that make me think one should be cautious about using it for many conclusions. I guess one could conclude that there is lots of variability in measured CdA across different kinds of bikes but I'm not sure what else could be said.

One thing I have noticed is that there is some "missing" power when I ride my Aero. About 4%. Since I tend to ride uprights more frequently, perhaps it's due to lack of bent-specific conditioning.
Perhaps, but what would that bent-specific conditioning be?

...Perhaps, but what would that bent-specific conditioning be?

I don't know. I have pledged to ride the 'bent for at least a year before drawing conclusions.

I would not be surprised to find that the perceived increase in speed when moving from a DF to a bent is at least partly due to increased time spent riding. After all, no one disagrees that bents are more comfortable.
Also, the records and such do seem to indicate that as you approach the higher end of either style, the difference between them is very, very tiny. But the athletes who set the recumbent records were almost certainly in less pain after the effort. Hmmmm.... that might be why recumbent teams are starting to do better in RAAM, which is after all a very long ordeal.

I attribute my speed increase to the fact that I've gone from a standard road bike to ultra-fast recumbent models. When I hop on my hybrid, which was my commuting bike in my pre-bent days, I am the same speed on it as I have always been. In my case, it is my recumbents, not me, that are several mph faster than my old road bike.