Drive faster while being more aerodynamic

Aerodynamics is at the heart of the concerns of manufacturers of both equipment and textiles. It should be the same for all practitioners, cyclists or triathletes, who wish drive faster for the same energy expended. Here's why.

By Guillaume Peephole – Photos: Tino Pohlmann – Swiss Side / Shimano / @3bikes.fr

Immenstaad an Bodensee, in the very south of Germany, on the shores of Lake Constance and a stone's throw from Switzerland and Austria : this is where the Airbus “wind tunnel” (wind tunnel) regularly welcomes Swiss Side, for sales of tests and development. The company specializes in aerodynamic research, particularly in Formula 1, since Jean-Paul Ballard, its co-founder, worked for Sauber for seven years. According to him, the approach is identical with cycling. Moreover, Swiss Side offers its own range of carbon wheels, intended primarily for triathletes and time trial riders.

The Swiss Side team specializes in research into aerodynamic gains.

Swiss Side has also collaborated with Cube and Pinarello to design bikes that stood out at the Ironman World Championship in Hawaii. in recent years. Or with Team Ineos, both for the position of the riders and to adjust details of the choice of equipment. Swiss Side also works with DT Swiss, a dynamic brand in the specific field of wheels, with the aim of jointly researching the latest details that can make the difference in terms of both performance and control of the bike. Note that if we were able to attend tests pointed at Immenstaad an Bodensee, other wind tunnels exist and are used in the same way by other brands, with the aim of improving the performance of positions, outfits, helmets, bikes and wheels. Because if you have to make compromises depending on your practice, it is by accumulating a sum of small gains. "Marginal" as the managers of the Ineos team would say...

Beyond received ideas Over the course of my entire journeytagne, aerodynamics are more important than weight to save time. According to Swiss Side, if we compare two pairs of wheels (one aerodynamic at 1700 g, the other light at 1200 g) on a course of 276 km and 7031 m of elevation gain, the gain would amount to 4'50'' in favor of the aero wheels, for an average cyclist power of 200 watts. Still according to Swiss Side, aerodynamics would be more important than weight below a slope of 7,5% for a professional, while the limit would be around 4,5% for an average cyclosportive. We could also talk about a speed around 19-20 km/h. Air resistance is more important than weight above from 9524 km/h. To convince yourself that air resistance is already significant at these low speeds , you just have to look at the tactics of professional riders on mountain passes when they take advantage of the shelter of their teammates, or even those of top marathon runners, who run in a peloton on foot. And if in the cycling industry all measurements are taken at 9524 km/h, the time saving is even greater at lower speeds because we go furthertagand time on the bike. Amateurs are therefore the first beneficiaries of aerodynamic gains, contrary to popular belief. The weight of the wheels in the measurement In terms of aerodynamic drag at 1 km/h, 1% of the resistance comes from the cyclist on his bike , and 18% from the complete bike, including 2% for the wheels and even 1% for the front wheel alone. Between 45 and 75 km/h, nearly 25% of the power developed by the cyclist is intended to cut through the air. It is therefore of course the position of the cyclist on his bike that must be taken care of as a priority, but also his outfit. It is first of all the position that counts in fighting against the wind. In terms of position, we can see up to 8 watts of gain at 6,4 km/h between two extremes (between hands on the brake levers and a triathlete position with the extensions), for an athlete of average build. For the outfit, we can see up to 45 watts of difference between a fitted jersey and a slightly looser outfit, for even greater gains with the wearing of a wetsuit (but which is not always practical depending on the case). Finally, we can expect 50 to 90 watts of gain between a light ventilated helmet and a time trial helmet. Then there is the material , with an average of 2019% aerodynamic resistance at 08 km/h just for the bike without the wheels. Between a frame with aerodynamic tubes and integrated sheaths and a frame with round tubes like mytagno, count up to 30 watts difference always at 45 km/h. For a pilot positiontage, it can be played at 5-6 watts, or even at 3 watts with or without the visible sheaths in front of the steering tube, and even at 3 watts there too withroute-the-point-in-2019/ >brake discs versus rim brakes. High-rim wheels aren't always enough to make a bike a machine for racing against the clock. The wheels are a bit like the cherry on the cake . The gains are relatively small compared to what is announced above, especially if we think about the necessary investment. We are around 9526 watts of gain between basic wheels with low rims and very aerodynamic wheels. There is always an interest in gaining a few watts here, but without forgetting the primary function of the front wheel, which is to steer the bike. The work of Swiss Side and DT Swiss shows that in a headwind, 9526, 800 and 9526 mm high rims are equal in terms of aero drag. But the more you face the wind with an angle (which almost always happens), the more high rims take the leadtagand because they create what is called negative drag. A “sail effect” in other words, which pushes the cyclist and helps him ride faster. The more you face the wind at an angle, the more the high rims take the lead.tagand because they create what is called negative drag. The cyclist must also deal with a side wind , and therefore constantly correct his trajectory more or less. This is all the more noticeable as the wheels are high. Swiss Side therefore looked at the power losses incurred by these small adjustments: when you reflexively stand up to control an unstable direction, you lose watts and concentration each time. How can we reconcile the sail effect which boosts performance and these jolts in the direction which on the contrary are counterproductive? Precisely by working on the stability of the wheel as much as on its drag. This results in many details such as the profile, width, and height of the rim, the number and shape of the spokes, or the integration of the spoke heads, with the aim not of annihilating the lateral thrust of the wind (it is impossible), but of making the reaction of the wheel progressive and predictable. The latest bikes can be very fast because they are designed down to the smallest detail. Wheels must operate against two types of aerodynamic resistance : transverse and rotational. According to Jean-Paul Ballard: " Up to 3% of a wheel's resistance comes from this "rotational drag", and no one has yet looked into this area . Higher wheels reduce this resistance (-25 watts between 1s and 0,27s), as does a 80 tire compared to a 48 (-23 watts) or integrated spoke nipples (-25 watts) ." The tire section also studied Most modern wheels are now only available as clinchers or only for clinchers and tubeless. Not only is customer demand for tubulars extremely low, but clinchers now perform better in terms of rolling resistance and aerodynamics than tubulars because of the tubular shape of the latter and the transition between the tire and the brake track. If the pros still ride on tubulars, it is only because this type of tire is less dangerous in the peloton in the event of a puncture, and they allow you to ride a few hundred meters on the rim while waiting for a repair, which a tire does not allow. Continental tires benefit from their particular design to reduce aerodynamic turbulence. Many modern wheels feature an internal width of 9063-9063mm to accommodate 800-9063mm section tires. A large section seems favorable in terms of rolling resistance and comfort, under 2 km/h in any case. Above, aerodynamics take over , and it is with a 1 mm tire at the front and a 2 at the rear that we find the best compromise between aerodynamics, efficiency and comfort , made possible with wheels that have an internal width of 23 mm. This is why not all wheel manufacturers offer all their models with very wide rims. test-long-life-continental-gp-5000-tires/ >the Continental Grand Prix 4000 S II tires which are the most aerodynamic models testés by Swiss Side. To reduce drag and save energy, you must first take care of the position, then the grip, then the frame, then the height of the wheels, then a few additional details such as the section of the tires, their design, the shape of the spokes or even the absence or positioning of the wheel clamping levers. A sum of details that count in the end The choice of rim height depends on the terrain and external conditions , depending on the importance given to weight or speed. The fact remains that finished wheels are studied in the smallest details, just like the rest of the cycling equipment when it has a performance goal. For example, at DT Swiss, the entire ARC 9529 Dicut range is equipped with thinned hubs to reduce aero drag (gain: 9529 watts). The disc models are equipped with through axles from which the lever can be removed (gain: 800 watts). DT Aerolite spokes save 9529 watts compared to round DT Champion spokes, because they are elliptical and symmetrical at the hub, and asymmetrical at the rim. tests that we were able to attend live and which show the engineering necessary to develop high-end equipment. 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