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

Yesterday I read Dan Wuori's article on VeloNews , a partial response to Mike Rosen's opinion in the Denver Post: Bicyclists take backseat to vehicles . There's an all-too-common argument made which is "car drivers pay for the road so have higher priority". This goes way back. It's simply incorrect: direct fees from car ownership don't cover the cost of the roadways, which are subsidized by the general fund. And in any case driving is externality-rich, so even if the fees covered the roads (which they don't) from an economics perspective they should additionally cover the externalities (pollution, congestion, road damage, CO2 emission, wildlife destruction; I could go on), and by any reasonable anslysis, especially in the United States with fuel taxes lower than they've been since at least before the 1970's in a percentage basis, they don't come close. But it simply doesn't matter. It's all a red herring. Because we don...

After the data presented by VeloNews on the effect of going from 23 mm to 25 mm tires, at the same pressure, on vibration reduction (measured with accelerometers: see this post) I was inspired to get fatter tires for the MDR ride (which I described last post). Bicycle Quarterly has published several reviews and tests of the rolling resistance of randonneuring tires, and the Gran Bois tires, "hand-built" by Panaracer in Japan, have always tested well. Jan Heine, the publisher and main contributer to Bicycle Quarterly imports these tires and sells them through his web-based retail business, Compass Cycles , so can be said to have a profit interest in reviewing these tires positively. Neverthless, his reviews are well written and his tests are well documented, so I had good reason to believe him when he said they are supple, have good rolling resistance, and are comfortable. When I saw them for sale in Box Dog Bikes in San Francisco , that sealed the deal. Bicycle Quarte...

After much speculation and indirect guessing, I finally got a time for Chris Horner climbing Sierra Road during stage 4 of the 2011 Amgen Tour of California. Recovox News VeloNews posted Rory Sutherland's power data , with analysis, for the climb. Rory started the climb in Horner's group and finished 1:15 behind. According to the article, Sutherland's time was an impressive 18:02. However that puts Horner's time at an amazing 16:47. I'd put maybe 2-second error bars on that number. For example, if Sutherland hit the base of the climb one second after Horner, then Horner's time would be one second longer. But I'll stick with this estimate. Sierra Road climbs 536 meters according to my numbers. So plugging that into Chris Horner's 0.280 hour ride and you get a VAM of 1916. Generally in the Tour de France if you see a VAM in excess of 1700 that's extraordinary. 1916? But in addition to overcoming gravity when you climb (producing ...

I'm really enjoying the recent series of VeloNews bike test articles. First it was aero mass-start road bikes ( April 2011 issue ) and now it's "endurance" bikes ( June 2011 ). This one is especially interesting because while there's already plenty of windtunnel data out there, vibraton data is less readily available. Wind tunnel tests are extremely trickly because the result depends so strongly on the size of the bike chosen, what's bolted on it, and the position of the rider. With vibration testing, we're getting closer to fundamental engineering, and I would hope the results would tend to be less dependent on assumptions. VeloNews isn't the first to do such tests, of course. I've already commented on Champoux's work in which he analyzied the spectral distribution of vibrations transmitted to a bike frame using a treadmill with a bump attached. Hastings did a study , also with a treadmill with a bump, at M.I.T. comparing old Cerve...

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 ...

In the September 2010 VeloNews Magazine , which I just got in the mail today, there's a review by Zack Vestal of six aero wheel pairs Check out the magazine for all the numbers. The topic of this blog post is the rating system. That system is to rank each of the six wheels from 1 to 6 in the following categories, then to average those rankings to get a final score: Aerodynamic drag weight front wheel stiffness rear wheel stiffness rear wheel rotational inertia front wheel rotational inertia Rotational inertia describes how hard it is to change the rotation rate of an otherwise stationary wheel. For a given unit mass, its contribution to weight is obviously proportional to the mass, while the contribution to rotational inertia is proportional to the mass multiplied by the square of the distance of that mass from the axis of rotation. So mass at the rim contributes more to rotational inertia than mass at the hub. First, note that three of these rankings depend on mas...

I really enjoy Lennard Zinn's articles on VeloNews. I don't always agree with his views, but I often find insight there. Today was an exception . Kestrel's latest Talon SL: very slick. He was asked about the benefit of aerodynamic road frames for mass-start racing. These frames claim to save approximately 1% to 2% of total wind resistance. There's a bunch of them. Kestrel was really the first to my knowledge with their carbon fiber Talon, although that failed to catch on among the mass-start crowd. Cervelo was the first to really break through with its aluminum Soloist, followed by Soloist Carbon (SLC), SLC-SL, and finally this year the S-series. More recently, Felt (with its AR) and Ridley (with its Noah) have jumped on board. There's still others. Chris Boardman claims to be testing an aero road frame. Yet the pros are sometimes reluctant to take advantage of these. While Cervelo was largely successful with its SLC, and even more so with its S3, at get...