John Cobb, the mastermind behind crowd-pleasing products such as the V-Flow Saddle, took some time out of his busy schedule to shed light on the mystifying world of cycling aerodynamics. Typical of his teaching style, Cobb's explanations of the time-savings value of race wheels and aero helmets were straightforward and really informative. So much so that we thought it would be best to print our interview with him verbatim. Of course, if you have any other questions feel free to call, email or ask any of the staff in the shop and we'll be happy to find an answer for you.
J&A: Recently, we've read a lot about the cost effectiveness of the time savings of an aero helmet versus race wheels. What do you find to be true?
JC: Aero helmets do save time but not in the same way as wheels. Wheels directly save watts,
or the amount of energy the muscle burns per stroke. Helmets help manage the airflow but do not directly effect the muscle usage. A good helmet can save 10 -15 seconds over a 40k distance, race wheels can save a couple of minutes.
J&A: How does one go about choosing the right areo helmet?
JC: The riders shoulder and back shape determines the best choice. There are two basic back shapes [A] Flat with an acute bend at the waist and [B] back flexibility at the shoulder blades with a pronounced hump in the upper back.There are about 75% more [B] style riders, [A] style riders are generally more aero and more powerful. [A] style backs usually do better with longer tail helmets with enclosed bottoms (Spiuk, LAS Laser, Specialized) while [B] shape riders do better with shorter tail helmets, Rudy Project Wingspan, LG Rocket, Giro to name a few. Most riders, either [A] or [B] are equally as fast if the tail of the helmet is up or down so it's not very important to try to maintain perfect position.
J&A: At what stage in an athlete's involvement in the sport is it a good idea to invest in a set of race wheels?
JC: When a racer decides to enter their first event, they should consider race wheels. The old thinking of "training on heavy wheels will make you faster" has consistently proven to not be true. Race wheels will help you have a better run in the events by saving you energy during the bike leg.
J&A: How do the different depths of race wheels affect speed? For example, if a rider averages 16.5, 21 or 23.5 mph, what depth wheel would you suggest for them? How would it affect their ride?
JC: Racers should always use the deepest rear wheel possible, the front wheels depth determines the bike stability in cross winds. The deeper the wheel the faster the wheel, rim shape and width is a very small overall factor. A 50 - 60mm front with a 90 - 100 rear is a great setup. The rider speed doesn't matter, the wheels are saving watts of energy.
J&A: How would environmental conditions (ie: wind, precipetation, and terrain) affect you answer to the question above?
JC: If you are a light weight rider, under 130lbs. or if you are unsure of your bike handling abilities, then use a shallow [25 -35mm] front wheel. At a race like Kona where the winds are legendary, go with a shallow front and deep rear. For heavier riders on rolling courses, I would use as deep as you can get on the front and rear. If you go where the hills are very steep and the decents are over 40mph. I would suggest a shallower front wheel.
J&A: What is your favorite race setup?
JC: I ride a 50mm front and 100mm rear at most of the races I do, I'm a 18.5 - 19mph rider. I would use a disc when possible because they are cool looking, oh and measurably faster. If you are a fast biker and plan to race for the lead, a deep front [90 -1080, H3] and disc if possible is my favorite.