On Bicycles, and.... what else is there?

First I saw it on the UCI list of approved frames for June , then I saw a teaser video posted to the Trek website , and then this uncredited photo was posted to the Weight Weenies forum: My that looks fast. Maybe it's the color, but it reminds me of the Canyon Aerooad. The Canyon has done rather well in the tunnel, not in the class of the Cervélo S5, but fairly good. See for example Tour magazine data here . So I expect the Trek will be at least this good. But then there's weight. The Madone 7 was quite light with the vapor coat -- under 800 grams. But then the Emonda came out, pushing that lower, but there's only so far you can go below that. So the Madone was a bike of compromise. Now they want you to buy two bikes: the lightweight Emonda and the "aero" Madone. So the pressure's off on weight. But I wonder how they did. Nothing on this one looks particularly heavy. From what I see I really like it. The days of bad-riding aero frames are over...

As was pointed out to me by Claude B in the comments section of a previous post, Argon has a new aero frame out, the Nitrogen ( web page here ), and with it they show some wind tunnel data: These tests are following a pattern. The Cervelo S5 remains the standard against which new frames compare, and they may be competitive with the S5, but don't beat it. We saw the same thing with the Parlee ESX and Felt AR1. Then lagging behind is a set of usual suspects, including the Specialized Venge and the Scott Foil. The only test I saw where the Scott Foil did exceptionally well was the test data produced by Scott itself. Between the Nitrogen and the S5 is basically a choice between low-yaw and high-yaw drag. The Nitrogen appears to do a bit better at higher yaw. I tend to err towards lower-yaw performance because of ground shear: yaw at the height of a downtube is less than it is, for example, at head-level, let alone at 10 meters. At extreme yaws control becomes a bigger issue...

At EuroBike, Cervelo made two huge product announcements, a new S5 aero-road bike, and a revised on the super-premium "would be fun to ride but I can't comprehend paying $10k for a frame and fork" "Project California" RCa. The S5 is an interesting case. Cervelo has a range of aero road bikes: the S2, S3, and S5. The S2 and S3 are the same frame but with different part specs. These were designed for the more average rider/racer, with an aero front end combined with the rear triangle which is basically the same as the R-series road frames. The S5, on the other hand, was designed with the racer philosophy that, as Specialized tweets, #aeroiseverything . The idea is that racers, looking for all marginal advantages, would ride the S5, and give up a bit of rear-triangle comfort. Surprise, surprise. On the Garmin pro team, the S3 got much more use. Racing is a complex dynamic, much different than riding solo in the wind. The riders felt better on the S3 wit...

For a long time I've been alarmed by the trend in carbon bikes to go to fatter and fatter tubes in a never-ending quest for higher stiffness-to-weight ratio. Indeed the trend predates carbon fiber: it goes back far further, to Cannondale, and before that, Klein with their fat-tube aluminum bikes. To save a relatively small amount of mass, giving up a large amount of wind resistance. But then as the quest for lighter carbon frames started approaching a limit, there was an effort to gain performance elsewhere. So wind resistance got renewed interest. Starting perhaps with the Kestrel Talon, there were a series of "aero road" frames which, at the cost of around 200 grams more or less, performed much better in the wind tunnel. These frames had a hard time catching on with professional riders, however. Road cycling is performed mostly in packs, with fatigue and avoiding crashing both major factors, so optimizing the bike is a lot more than optimizing speed at a given po...

I was floored by what I've seen by the new Cervelo RCa , which was just announced. The thing comes closest to perfection in a diamond-shaped bike for it's geometry that I've seen. A very brief digression: In the past, bikes are designed for fit and stiffness and mass. Aerodynamics was always a factor, but it was relegated to fit: for 100+ years riders have realized they could go faster if their backs were flatter. But all bikes were made out of the same 1-inch steel tubing, as this worked well. That changed in the 1980's, when Klein came out with his Al frame. With Al, the tubing can be made thinner with the tube diameter larger to get improved stiffness at lower mass. Other companies, like Cannondale, picked up the same trend. This flaunted aerodynamics, since the fatter tube bikes have more wind drag. But the effect of the increase in wind drag was quantitatively hard to assess, while weight and stiffness are directly detectable, and riders kept winning rac...

Back in July 2009 I did a series of first-order calculations on the effect of various parameters on riding speed. Calculating speed from power is difficult to do explicitly, but to first order the calculations become straightforward. First-order analysis is where much of the intuition is, anyway. One of these calculations was the effect of wind resistance on riding speed . Then in November 2009 I extended that analysis to the effect of wind speed on riding speed . To my dismay, I found an error in that result. I'd even rationalized the wrong result with incorrect arguments. I had to track the consequences of that error through the following two blog posts. I think I fixed everything. The corrected result was: d s / d s w = 2f / [ 2f + 1 ‒ s w / s ] where s is the rider speed, s w is the tailwind speed, and f is the initial fraction of retarding force due to wind resistance. There appears to be a singularity issue for strong tail-winds (see the denominator) but then ...

I've long been frustrated at the lack of bars in my preferred size, 40 cm o-o or 38 cm c-c. My shoulders are relatively narrow, and when I go to wider bars, I feel like I'm in a less stable position, with arms spread out. If I'm holding the plank position, I want my hands directly under my shoulders, and on the bike it's the same. This is the position of greatest mechanical strength. On top of this, narrower bars are more aerodynamic and have less of a cross-section for contact with adjacent riders. It's win-win. Yet for some reason wide bars have been popular. People feel they can get more leverage on wide bars. But power on the bike comes from the legs, not the arms (tests have confirmed this). To maximize this, you want to have as smooth and fluid a pedal stroke as possible. That implies staying balanced on the bike, not wildly thrashing about. So I think any benefits of wide bars except in violent sprints are over-rated. But what about violent sprint...

CyclingNews published a gallery of photos of the Astana team getting tested for bike position by Specialized. Of particular interest was the position changes given to Viscenzo Nibali, their new star for stage races, who rode for the Cannondale-sponsored team last year. Presumibly the superior fit provided by the Specialized crew led by Andy Pruitt would improve Nibali's time trialing. I was curious in how the position change, so I superposed the before and after photos in the article. To align the photos, I rotated and scaled them to align the arm pads. According to the article, "Nibali's bars were raised so he could try to relax his shoulders and drop his head". However, to me if anything his "before" shot looks more relaxed, with a lower head and a more aerodynamic position. If on top of this you shift his "after" position up (the bars being higher) the advantage of the before shot appears even greater. Of course, there's alwa...

The trend continues that the big bike companies (manufacturers isn't quite the term, since so few of them actually manufacture anything... perhaps "branders" is a better term...) are delivering aerodynamically optimized road frames designed for use in mass-start road races. These bikes go way back, at least as far back as the Kestrel Talon. But the use of the bikes at the top pro level really began with the Cervelo Soloist (Bobby Julich won Paris-Nice on the bike). Then the Cervelo SLC and SLC-SL really got things rolling. Then Ridley came out with the Noah and Felt with the AR, and Fuji with the SST. And these are just the bikes of top-level pro teams. Kestrel updated the Talon (and Talon-SL), and Litespeed came out with its stunning Archon-CF; neither of these bikes got pro-level attention, however (Kestrel briefly sponsored third-tier Rock Racing, but Rock used their stiffer RT-800). Yet except for the Cervelo, all of these frames seemed to encounter resistance...

The Specialized Venge made its debut at Milan San Remo this year, and it couldn't have gone any better for the Morgan Hill company, as Matt Goss, a relative underdog, won the race. Move on the Tour de France, and with aerodynamically optimized mass-start road frames more popular than ever, Mark Cavendish has pulled out two impressive sprint victories on the bike in a first week notably unfavorable to sprinters. Last year when HTC was sponsored by Scott instead of Specialized, Cavendish rejected his Scott Foil (then F01) in favor of his tried-and-true super-beefed-up Addict, so once again this looks good for Specialized. Venge spotted at Mike's Bikes in San Francisco But the frame is only a relatively small part of the aerodynamic picture. Far more important is body position. So here's photos of Cavendish during his two victories this year... first stage 5: CyclingNews Then stage 7: CyclingNews These photos aren't cherry-picked: they're the first...

I'm working my way backwards through Bicycle Quarterly and am currently at the Fall 2007 edition. There's a very interesting article there: Jan Heine went to the wind tunnel to test his Alex Singer Randonneuring bike with various options. One of the tests was the effect of a front fender. As he expected, the front fender appeared to reduce wind resistance. He used a telescoping fender to test the effect of length. I plot the result here: "N" corresponds to no fender, "S" for short, "M" for medium length, "L" for long, "XL" for extra-long, and "MF" for a mud-flap on an extra-long fender. There appears to be an optimal length: the fender blocks the wind from entering the brake area, then going longer than that is counter-productive. Jan dismisses the effect as relatively small. However, ignoring his "repeatability" tests to establish error bars, I'll plot the naked numbers of the difference ...

A few more plots on the Scott Foil comparative windtunnel data... First VeloNews. Both Cervelo S and Felt AR frames were tested by both VeloNews and Scott. VeloNews tested the Masi Competizione, which they claim is similar to a Trek Madone. Scott tested the Trek Madone, so I include the results from these tests as well. VeloNews' tests were with Zipp 404 wheels except for the Masi which was tested with Fulcrums. However, I adjusted the VeloNews data based on the (considerable) improvement the Zipps had on the Ridley and Cervelo in their test, which were each tested with both the Fulcrums and the Zipps. VeloNews tested at positive and negative yaw, while Scott reported only wind from one side of the bike, so I averaged positive and negative data from VeloNews. In each case, both for the North Carolina windtunnel used in the VeloNews test, and in the Mercedes windtunnel used by Scott, I assumed an air density of 1.2 kg/m³ to convert from force (VeloNews) or power (Scott) to...

Scott just released a new bike, the "Foil" , their entry into the "mass-start aero frame" category. This bike has been around in the pro peloton for a year now. Mark Cavendish famously rode it in the first stage of last year's Tour de France, where he had a disappointing result. When he switched back to his previous bike, a beefed-out Scott Addict (the consumer Addict is under 800 grams, Mark's custom bikes are reportedly close to 1200 grams with a Pinarello-like excess of carbon fiber), he started winning races again. But the rest of his HTC Columbia team continued to ride the bike, including Mark Renshaw and the rest of the lead-out train on which Mark relies so heavily for his wins. Interestingly, until this consumer release it has been called the F01. Very clever: the F01 becomes the F01L, or the "FOIL". Scott wins the bike naming game against Specialized with the latter's recently-released Venge. The differentiating factor with ...

Both the VeloNews aero bike test and the Tour aero bike test (my discussion of that test is here ) examined the Cervelo S and the Tour AR. In the case of VeloNews, the bikes were tested "stock" with the exception both used Zipp wheels. Cables were installed and there was no rider. Tour on the other hand used a dummy rider (the only way to get a reasonably consistent position) and Mavic wheels. The Tour article is in German, so the finer details are beyond my comprehension. But they didn't use bar tape, while VeloNews used whatever bar tape the bikes had installed. Same deal with the saddle: the VeloNews bike tested bikes with "stock" saddles, while in the Tour test, the saddle was less important due to the use of a "rider". Despite differences you might think conclusions about which bike was faster would be fairly consistent. But comparing the only two bikes tested by both magazines, this is not the case: I averaged the positive and negati...

I've been spending a lot of train time playing around with puzzles, doing "work-work", and even reading the newspaper following recent world events. Time to get back to those VeloNews frame data. VeloNews plots its drag force in grams. Grams is not a standard unit of force. A "gram" of force is defined as the force exerted by a standard gravity on a one-gram mass. But with wind resistance, we're probably most interested in power. And to get watts from force we want the standard metric unit of force, which is Newtons. Newtons multiplied by meters/second equals watts. So I converted their data to Newtons. But even then, Newtons are good only for the relative wind speed at which they did the test. Actual force depends on relative wind speed and air density. Wind resistance force is generally proportional to the product of air density and the square of the relative wind speed. I don't know the air density, but I can guess it was close to 1.2 k...

Earlier I reported on a Tour magazine windtunnel test of various "aero" mass-start road frames. Here was the plot from that magazine: Tour magazine windtunnel data Soon after, VeloNews , in its April edition, followed up with tests of its own on a set of its own "aero" bikes. You can read the article here , courtesy of Cervelo, which fared best in the VeloNews test. It is curious to compare the two, because the conclusion which are drawn from the two tests are substantially different: Tour used a dummy rider on each bike, using a hinged stem for handlebar placement, while VeloNews tested the bare bike Tour omitted cables, a potential source of variability due to uncertain cutting and/or placement, while VeloNews included cables. Tour omitted handlebar tape, while VeloNews used whatever tape was "stock" with the given bike. Neither test used any waterbottles VeloNews tested bikes with two sets of wheels: stock and Zipp 404s. Tour used a single ...

Many years ago, Kestrel Bicycles came out with the "Talon" road frame which was targeted as spanning the bounds between triathlon and mass-start racing. There were no wind tunnel data, no scientific tests: it was simply designed to look aero, and who knew if it was or not? Kestrel, who was among the early groundbreakers in building and selling carbon frames, was sold by a Japanese group. However, the Talon survives, both with a standard model and a lighter a Talon SL . It got redesigned for 2009 ( see video review ). I've always found the bike attractive, in part because of its Santa Cruz roots. Years later Cervelo, a long time leader in time trial frames, came out with their Soloist aluminum-frame bike. CSC showed the bike to be quite race-worthy at the highest level, notably with Bobby Julich winning the 2005 Paris-Nice . Then they developed the SLC, a carbon version, for that year's Tour de France. An SLC-SL followed in 2006, and for the 2008 Olympics, t...