Advanced, Cycling, Gear, Podcast, Technology

Aerodynamics mastery and free speed on the bike with Nuno Prazeres | EP#25

 May 26, 2017

By  Mikael Eriksson

Aerodynamics mastery and free speed on the bike with Nuno Prazeres | EP#25

Nuno Prazeres is a competitive Portuguese age-group triathlete and That Triathlon Show listener with great attention to detail.

He has really managed to get the most out of his bike power by optimizing his aerodynamics and using other hacks to get free speed on the bike.

In this Episode you'll learn about:

  • The 11 boxes Nuno checked to master aerodynamics and free speed.
  • The gear that will give you the best aerodynamic benefits.
  • How much time does shaving your legs really save?
  • The mindblowingly effective (and free!) paraffin and tire pressure tricks that can save you 10+ watts
  • Everything is backed up with numbers: how much time or how many watts do you save by doing this or that


Background on Nuno Prazeres

  • Listener of That Triathlon Show from Portugal
  • Started triathlon a long time ago but moved away from the sport for 15 years. Then he came back mostly to enjoy the pleasure of doing long distance triathlons.
  • Currently preparing for an Iron distance race (Challenge Roth) in the 50 year old age group.
  • Entered five 70.3 distance triathlons recently locally in Portugal and is competitive. Won some of his races.

​1. Buying a power meter to be able to calculate your drag coefficient, your CdA estimate via software (Dr. Chung Aerolab in Golden Cheetah).

  • Typically when we spend watts on the bike, more than 85% of the watts we are spending are spent fighting the wind, fighting air resistance.​
  • The power meter is an instrument which creates sort of a virtual wind tunnel that helps us to access what are the effects of the changes we are doing on a bike to create a relationship between the power generated and the speed.
  • There are at least two or three software accessible either through download like Golden Cheetah or browser based like Best Bike Split.
  • Nuno uses a PowerTap power meter that measures power from the hub, so it accounts for every possible power loss from he force applied to the pedals through the drivetrain. 

2. Doing a bike fit. Nuno did a bike fit himself aiming to reduce drag without compromising function. And he filmed himself in slow motion on the rollers from the front and the side and used the software tool to measure angles and areas.

  • Although Nuno doesn’t recommend this to everybody because his body type is quite similar to the test dummy that Cervelo uses in their wind tunnel which is based on David Zabriskie, a former cyclist. This means that most of the geometry of the bikes fit himself quite well.
  • Nuno strongly suggests to find a good bike fitter than doing the work yourself. You can spare 100 euros or 150 euros more or less by trying to do it yourself. But it’s a risky process. Bike fitting is a very serious matter because it can condition yourself and you can even - if not properly done - injure yourself.
  • Resources: Cody Beals' blog and

3. Buying an aero helmet. The one size fits all principle does not apply here. The shape of the helmet is very important and should suit your riding style.

  • If one tends to ride with the head very upright or looks down a lot, the person does not need a huge tail in the helmet.
  • Professional bike fitters can help as well in choosing the helmet.
  • On a sprint triathlon, regardless of power, you can save 15-30 seconds.
  • For an olympic distance triathlon, 30-60 seconds
  • For half distance triathlons, 1.5-2.5 minutes
  • For Ironman distance triathlons, 3-5minutes
  • Nuno uses a Rudy Project Wingspan helmet
  • Reference: Dean Philips, Fitwerx.

Key takeaway

An aero helmet is one of the most cost effective ways to get a significant aerodynamic improvement.

4. Buying a skin suit. To be as smooth as possible when riding because because a triathlete accounts for more than 80% of wind resistance on a bike.

  • This lowers the drag coefficient by 1 unit, saving 10-15 watts of power for the same speed.
  • Need to be fit without wrinkles but still provide function.
  • Reference: Cycling Weekly
“We’ve already tested the benefits of wearing a skinsuit instead of a normal jersey and bibshorts and the results speak for themselves. On a 25-mile time trial ridden at 25mph, the skinsuit saved around five watts on both a normal road bike and a TT bike.

With the right fabric technologies and seam positions, it is possible to save between 10-15 watts even in top-end suits, which is significant in the world of TT racing.”

5. Buying Continental GP 4000 23mm tires as the best compromise between aerodynamics, friction, rolling, puncture, and flat resistance.

  • But you can use a wider 25mm tire at the back because it’s sheltered from the wind.​
  • A Flo Cycling article describes wind tunnel test results that backs this data up
  • For example, compared to the Continental Gator skin tires, the GP 4000 tires save 3 minutes over an Ironman.

6. Optimizing tire pressure. Your weight is not distributed evenly on a bike, so the tire pressure in the front and rear tires should reflect this.

  • On a road bike the distribution is typically 60%-40%, with more weight on the rear wheel. So 60% of the total tire pressure should be in the rear tire and 40% in the front. 
  • On a tri bike, it’s a bit more biased towards the front.
  • The pressure that you put in the tire should take that into account to maximize the relationship between the function and rolling resistance.​
  • Place a scale in turn under your front and then your rear wheel to find your true weight distribution.
  • Resources: Check out this excellent white paper on the topic, and use this tire pressure calculator.  

Key takeaway

Don't put equal pressure in your front and rear tires out of laziness. Check your weight distribution over the wheels, and distribute pressure the same way.

7. Optimizing the between the arms bottle position. Cervelo did a test a few years ago showing that between the arms is the best position for a non draft bike to use the water bottle.

  • Nuno found a website in which the bike model that he is using is tested in a wind tunnel, and it’s showing completely different values if its mounted regularly or if it’s mounted with a lot of creativity - lowering the position of the bottle.
  • This goes to show that this kind of detail counts a lot and having the bottle at different positions on the bike can make a huge difference. You can use a power meter to test and find out what are the results.
  • When the bottle was in the standard mounting position, watts lost was -1.7W. Then when it was mounted upside down, it saved 8.3 watts.​

8. Shaving your legs. Typically, you can save more than 1 minute for per 25 miles.

  • In an article written by Alex Hutchinson, a reduced drag by about 7% saving 15 watts at the same speed which translates to a 79 second advantage over a 40 kilometer time trial.
  • It can easily get to 5 minutes savings in an Ironman distance.
"The Specialized aerodynamicists in charge of the wind tunnel, Mark Cote and Chris Yu, were so surprised that they tested five more cyclists before they would let Thomas publicly reveal the findings. The results were consistent: All of them saved between 50 and 82 seconds over 40 kilometres."

9. Using Paraffin as chain lube

  • This came from a Friction Facts article.
  • Paraffin is the major component of this lube.
  • It’s water repellent, so the chain does not get wet in rainy conditions. And when you touch the chain, your hands don’t get dirty. It lasts for 500 plus kilometers.
  • There’s data showing that you can save 78 seconds per hour. 
  • In an Ironman we are talking about 5-6 minutes.
  • Other stats from the Friction Facts article:
    • You can save 4 plus watts on chain lube
    • 3 watts by avoiding cross chaining
    • 1.8 watts on your bottom bracket, and
    • 1.3 watts for your derailleur pulleys.
    • So, 10 plus watts if you add those together.

10. Borrowing or getting a Zipp 404 front wheel. 

  • The front wheel is one of the most important components for aerodynamics.
  • According to Faster’s wind tunnel (Scottsdale, Arizona) engineer Jay White, compared to a Mad Fiber clincher the estimated times saved with this wheel is 70 seconds over an Ironman.
  • Nuno borrowed a Zipp 404 wheel for his race for free, and says that you can find them for around 500 euros on Ebay.

11. Using wheel covers on the back wheel to make it as aerodynamic as possible

  • ​This cost Nuno 100 euros from a wheel online shop in the US. 
  • Cody Beals who is very good with aerodynamics (coming from an engineering and physics background) uses aero covers on his rear wheels and has for quite a long time.
  • The conclusions from a wind tunnel study by Wheelbuilder were that:
    • A covered wheel has dramatically lower aerodynamic drag than an uncovered wheel.
    • Disc cover performance is virtually identical to disc wheels through the entire range of yaw angles: 0-30 degrees.
    • A covered 81mm deep wheel outperformed flat disc wheels in every wind condition. The covered Zipp 808 has less drag than the fastest disc wheel tested beyond 10 degrees of yaw.
    • A typical 30mm training wheel with disc covers approaches the performance of a flat disc at 7.5 degrees of yaw, but exceeds performance of all disc wheels tested at wind angles greater than 12.5 degrees.
    • The lens-shape on a disc-cover's non-drive side causes wind to pass around it like a wing, producing forward thrust. This effect is more pronounced on covered shallow wheels beyond 20 degrees of yaw.

Additional aerodynamics

  • Position endurance. Sustain a good aero position for the longest time possible.
  • Tie cables that are hanging together to eliminate turbulence and air drag.
  • Always use the best gear ratio in order to pedal at your best, most comfortable cadence.

Rapid-fire Questions

  • Favorite book, blog or resource related to triathlon: The book Triathlon 2.0 by Jim Vance, and the Real Coaching podcast from Paulo Sousa and Joel Filliol.

    Check out the That Triathlon Show interviews with Jim Vance and Paulo Sousa
  • Personal habit that helped Nuno achieve success: Consistency
  • Favorite piece of gear or equipment: The power meter or smart watch
  • What do you wish you had known or wish you had done differently at some earlier point in an earlier point in your triathlon career: Doing more polarized training or avoiding the gray zone in training

Links and resources

  • Send feedback to host Mikael by email
  • Connect and hit me up on Twitter - my handle is @SciTriat
Subscribe to That Triathlon Show and never miss an episode!

Mikael Eriksson

I am a full-time triathlon coach, founder of Scientific Triathlon, and host of the top-rated podcast That Triathlon Show. I am from Finland but live in Lisbon, Portugal.

Please contact me if you have feedback on the podcast or want to make suggestions for improvement or send in a question for a Q&A episode.

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