Hit your best triathlon bike split by nailing your suit, helmet, wheels and position

How much faster is a time trial helmet? Is a suit with sleeves faster than one without? Where should you put your water bottles? Tips to get you a triathlon bike PB this summer.

| May 16, 2018 | GEAR

Jan Frodeno, seen here at Ironman 70.3 Oceanside, has his bike position and equipment dialed in for optimal aerodynamics.

Jan Frodeno, seen here at Ironman 70.3 Oceanside, has his bike position and equipment dialed in for optimal aerodynamics.

Photo >Felix Rüdiger / Plan A GmbH

by Kay Dobat Cycling

Last April the folks from Dobat Cycling tested suits, helmets, wheels and body positions at their Monster AeroDynamic Days (MAD). Their research proved that when it comes to aerodynamics, there isn’t one perfect time trial suit or helmet that works best for everyone, but there are aerodynamic “tendencies” that can help athletes dial in their fastest bike splits.

The tests were not done at a Velodrome, as had been done for previous MAD Days, but instead utilized some of the strongest time trial riders and triathletes in Northern Germany using Aerotune’s technology.

Various manufacturers such as Biehler, Bioracer, DT Swiss, Kiwami, Ryzon, Schwalbe, PA Suits, Poc and Uvex provided Dobat Cycling with gear for the tests. Altogether there were 26 time trial suits, 19 wheel sets and 17 helmets available as test equipment.

You can find some of the test results and additional information on the www.dobat-cycling.de homepage.

    Here are some of the general findings:

    Triathlon/Time Trial Suits

    1. Time trial suits with long sleeves are slightly better than short-sleeved triathlon suits. The difference between the best time trial suit and the worst triathlon suit (the only suit without arms in the test) was 25 watts at 45 km/h.
    2. When it comes to suits, the results do seem to transfer reasonably well to other athletes. For example, the Castelli 3.0 was the fastest suit for four riders. Unfortunately, not all of the suits fit the test athletes well, so the testers deliberately evaluated only the aerodynamic properties of the suits. If you want to test suits, you should look around for a triathlon shop or a bike fitter with a selection of suits so you can try them out.
    3. When it comes to suits, fit is everything. If the suit folds, or if the seams are not pulled to the intended positions, the aerodynamics deteriorate.
    4. In recent years the best suits have incorporated several innovations – they do make a difference. Hidden seams, concealed zips, leg, arm and neck cuffs and special materials on the shoulder, arm and back surfaces ensure better aerodynamics. The special materials on these surfaces form micro vortices that ensure that the air flows more closely along the suit than on suits with smooth surfaces. This effect reduces the resistance.


    1. Aerodynamic tests on helmets are somewhat less conclusive than on time trial suits. With helmets the sitting position and, above all, the head position play a decisive role. With that in mind, your helmet choice should depend on your position.
    2. Regular (racing) bike helmets (including aerodynamically optimized racing helmets) cannot keep up with time trial helmets. This is due to the increased air intakes and the shapes. If you wear a typical bike helmet in a good time trial position (head low), you face the air with a large, flat front surface. Time trial helmets are specially developed for that position and have clear advantages. Another point that is evident in most of the newer time trial helmets is the widened front surface. This improves the transfer of air to the shoulders ...
    3. Between the best time trial helmet and the worst racing bike helmet the difference was  27 watts at 45 km/h. Even if you only look at the pure time trial helmets, there were differences of over 10 W.
    4. When it comes to helmets, there are numerous issues around the topics of comfort, ventilation, field of vision and fogged visors. Testers said everything from "I was really flying blind" to "What a perfect field of vision." As with suits, finding a fitter or tester with a variety of helmets can help dramatically when it comes to dialing in the best helmet.



      The MAD Days testing looked at a variety of wheels with a total of four riders (one on a racing road bike, three on time trial bikes). High-profile (deep dish) wheels are usually better than flatter (shallow) wheel profiles. The tests showed that the wheels function differently in different frames, which is why we’re starting to see several joint development projects between frame and wheel manufacturers. With that in mind, Dobat Cycling doesn’t want to publish any measurement results for the wheels.

      Even without specific details, though, there is some general information the testing showed:

      1. Tires mounted on front wheels that are wider than the rim usually has a negative aerodynamic effect. On a DT Swiss Dicut ARC 1100 front wheel (slightly smaller than a Zipp 808 Firecrest), for example, 23 mm wide tires are aerodynamically better than 25 mm wide tires, according to our measurements. The decisive factor here is not the width indicated by the manufacturers of the tires, but the actual width in the assembled and inflated condition.
      2. With the rear wheel, the position of the wheel in the frame is more important. Here the air flow is much more turbulent than for the front wheel. The shape of the rim, the spoke shape, the spoke nipples and the length of the valves also influence the aerodynamics.
      3. The tubes and tires have an effect on rolling resistance and thus also a direct influence on speed. Schwalbe provided us with tubes and tires for our tests. There were no problems over the 600 km of testing and the testers learned that the Schwalbe Pro One (tubeless ready) is slightly more difficult to install than the Schwalbe One (a folding tire for use with tubes) due to the smaller inner diameter of the tire. However, the Schwalbe Pro One has a lower rolling resistance in tubeless use because of the savings made by not having a tube.


        Antony Costas gets the most out of his position at the Laguna Phuket Triathlon.

        Antony Costas gets the most out of his position at the Laguna Phuket Triathlon.

        Photo >Kevin Mackinnon

        Other measurements

        Three riders were tested in different positions including: basebar/time trial position, various head positions, different hand and forearm positions, compared back positions (round and stretched) and looked at different bottle positions - on the handlebars, in the frame triangle and behind the saddle. Once again, individual tests were required to see what worked best for each athlete. Here are a few trends:

        1. Position is everything. A good position in which your able to provide the most power to the pedals, combined with optimized aerodynamics provides the most time savings compared to suits, helmets or wheels.
        2. The body position, especially the head and shoulder position, has the greatest effect on aerodynamics. Raising the forearms and hands (praying-mantis position) also has a positive effect on most riders aerodynamically and helps relax the arm and neck muscles.
        3. When it comes to positioning water bottles, they have less of a negative effect the further back you mount them – so they are better in the frame triangle than on the handlebar and better still behind the saddle. Aerodynamically shaped bottles are better than round drinking bottles.

        In conclusion

        Aerodynamics is not a single step, but a process. It is no coincidence that professional athletes invest several hours in aerodynamic measurements to optimize their position and equipment. Here’s a summary of our findings from our MAD Days tests:

        1. Postion is where you need to start. Athletes achieve their greatest success through a biomechanically optimized position combined with an aerodynamic position. Those should be taken care of with a professional bike fitting.

        You can still find some aerodynamic savings with your equipment:

        1. Racing suits don’t seem to be as rider-dependent as helmets. There’s a good chance that a fast suit on another rider will be suitable for you.
        2. That is not the case with helmets. The ideal helmet cannot be found purely on the basis of comparative values. Testers of bike fitters with more experience can help on this front – based on the position a good tester will have a feel for which helmet is most likely to work. This can easily be tested, too.
        3. There is lots of variability when it comes to wheels. To get the most accurate values, you need to make sure the wheels are tested in the correct frame and with the correct tire width.
        4. To dial in your best position and set up, you should do an aerodynamic test on the track or out on the road.