Ep. 11 Sponsor - BikeFit Education

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Fitting Aerodynamics and John Cobb

On the pod this week, I interview John Cobb. He is a pioneer & innovator in the bike industry since 1972 and is considered part of a handful of legendary figures that helped shape the bike industry. He is often referred to as “Mr. Wind tunnel” and has been a proven pioneer in the area of cycling aerodynamics to help position riders better in order to gain speed and comfort.  He’s designed or been involved with the design for virtually every part of the modern bicycle. His stories are almost as legendary as he is and John provides many of them throughout the podcast.

We focus on aerodynamics since John was one of the first to ever put a human inside a wind tunnel.  How he convinced the kind and intelligent people of Texas A&M to use the wind tunnel for cyclists vs. their usual car testing is quite amazing.  Regardless, John was relentless in spending his own money and time with some of the early pioneers of the industry to study the impact of aerodynamics on cyclists.  This lead naturally to bike fitting as he analyzed position changes and it’s aerodynamic impact but also the tradeoff regarding aero vs. comfort.

The Podcast breaks down into 4 major topics but as you’ll notice, I let John’s brilliant mind meander down the rabbit hole in any direction as only he can bring the most amazing stories to life.

1.) Coaching and bike fitting symbiosis

2.) Bike fitting

3.) Aerodynamics

4.) Crank length

THE DIVE: Ep. 11 Topics

  • Getting into the cycling business when a friend offered him bikes as a form of payment
  • History in cars, not bikes
  • John Cobb’s history before saddles
  • “You’re my last resort.  If you can’t fix me, I’m gonna quit biking,” says the cyclist. “I’ll take that responsibility,” John replies.

Coaching and Fitting Symbiosis

  • “Finding a good coach is like buying shoes, just cause somebody’s a good coach doesn’t mean they are a good coach for you.  So you have to be willing to make the change.”
  • “You have to build trust to really help someone”
  • Many people will not be honest about what they can do on the bike.  It’s the fitter’s responsibility to establish trust to truly help someone.

Bike Fitting and Aerodynamics

  • How John designed helmets for Rudy Project
  • Getting caught in the hype of aerodynamics
  • What makes a bike fitter great is experience.
  • John fitting athletes with real-time feedback out of the back door of B&L cycles in Hawaii
  • The journey of fitting for free around the country
  • The importance of age group athletes vs. professionals
  • Allow cyclists to self-select to find the right position.
  • The crossover between running form and bike fitting
  • John’s experience with pressure mapping software
  • In fitting, it’s important that the cyclist can’t see what the technology is doing

Crank Length

  • John’s work with Dr. Jim Martin
  • Case studies of crank length changes
  • “God did not command everybody to use 172.5 length cranks.”
  • The pinewood derby
  • The speed of aerodynamics
  • Crank length is a tuning tool
  • Crank length’s connection to chainring size

Everyone says your seat height is too low or your seat height is too high…You can take the 10 people that are the most gifted fitters in America and all 10 of them will come up with a different seat height for you.  There’s just not a math answer to that. People that use math, just purely math to set things, all they are doing is putting you in a position that is safe–that you’re not probably gonna get hurt. You’re probably not going be fast but you are not going to get hurt.  For a bike retail store that’s a good deal, but for somebody who wants to go win races, that’s not the right way.

John Cobb

Speed and Comfort

John Cobb has been an avid cyclist since 1973, going through the steps of recreational cycling, touring, road racing and getting involved in the new sport of triathlon in 1981. Triathlons were particularly interesting to John and he began to focus more on that area as he developed skills in fitting and designing bikes. John opened his first retail bike shop in 1981, always having a focus of making his customers faster and more comfortable. He began testing human riders in 1984 at the Texas A& M WindTunnel and soon developed a reputation and a following for delivering the fastest bikes and riders around the world. John has always had a natural curiosity and an ability to see something in his mind and then be able to actually build it with his hands to test his theories. He has designed frames, wheels, cranks, helmets, saddles, handlebars, clothing and virtually every other part of modern bicycles, having many, many designs and products that lead the way today. John has always been willing to explore the outer limits of different sports and his continuing research will hopefully help riders for many years to come.

Want to learn more about John’s current projects?  You can find his work below:




  1. Jake Brindle

    I’ve followed John for many years and finally got to meet him in Kona World champs one year(2014) He was so kind and approachable and his writings on Womens innies and outies helped me so much with my fittings! I’ve since stocked his saddles in my bike fitting business with great success!

  2. Todd Kenyon

    I am a big believer in short cranks as a fitter and triathlete and frequently use John’s 145-155mm cranks. But I have to question one thing John said at the end of the podcast – that you need to use bigger chainrings with shorter cranks. All other things equal (they are not in actual practice but stick with me), a shorter crank will require more force to generate the same torque at the BB spindle. If you then also use bigger rings (i.e., a bigger gear) then still more torque is required, so the force at the pedal is now much greater than with your longer cranks and smaller ring. To keep power constant, you would need to pedal at a much slower cadence. Yet, I am sure John has said in the past that everyone has a preferred angular velocity at the foot. At a constant angular velocity, a shorter crank means higher cadence (due to the smaller circle circumference for each pedal stroke). This matches my observations – folks speed up their cadence immediately with shorter cranks. To maintain power output, at a higher cadence you need a lower gear. Was wondering if John could clear this up…

    • Damon Wyatt

      Hi Todd–I reached out to John and here are his thoughts:

      “What I have found is that riders that are big gear mashers, usually at a lower cadence range (65-75) change to the shorter crank and they don’t like the feel even though they do see the improvement in cadence, going up a tooth on the chainring usually fixes that feel but if they would just give the shorter crank and smaller gearing a few days effort they would like that, have a higher cadence and go faster. Getting a racer to put in some adaption time has always been hard.”

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