by Garneau

In recognition of what would have been Lea Davison's first World Cup of 2020 and a shot at making the Olympic Team, we've chosen to tell the story of our collaborative pursuit of enhancing speed on a mountain bike.  Though, Lea will not be racing this weekend due to COVID-19, we still hope her rides full of sprints to some imaginery finish line because she has taught us #happinessisfast.

It began as a phone conversation. Lea Davison was looking to crush the upcoming season and tasked us with improving one fundamental requirement for her performance: speed. Our experience with aerodynamics in such a varied environment was minimal. Sure, we’d been in wind tunnels, but this seemed irrelevant to mountain biking.

So, to begin this adventure into the unknown, we consulted with our friends at Aerolab. Real-world aerodynamics is the next evolution in cycling technology. It is also the most difficult to achieve because the rider is a changing form and contributes to 75% or more of the drag. AeroLab set out to create a lab grade sensor that would meet engineer’s expectations and could eventually be user-friendly tool for any triathlete or cyclist wanting to be faster no matter their technical level. 

AeroLab has a really tight team and the right mix of staff passionate about cycling and sports. Top engineers, aerodynamicists, programmers and strategists are the underlying driving force behind AeroLab. But even to them, mountain bike aerodynamics was unexplored territory. Nonetheless, we decided to initiate the research.

Lea Davison
Lea Davison

The Testing Protocol

The process wasn’t different than AeroLab testing carried out with other athletes and equipment. However, special care and attention was paid to the lower ground speeds and the fact that the mountain bike rider would be more exposed and often more dynamic than a triathlete or cyclist.

The test protocol requires a closed-circuit course with consistent road surface conditions. The course in this case was an 800 [m] out and back stretch of roadway. Ideally, we choose a course which is comfortable for the rider, and this is key: the rider must be very consistent in their body positioning during each trial in order to diagnostically detect small differences in aerodynamics (e.g., differences in the order of 1-2%). Typically, this requires a professional or semi-professional rider since any recreational rider will exhibit too much variance in their own ability to maintain a body position, either through fatigue or lack of riding experience. In this case, we were in luck: a world-class mountain bike rider, Lea Davison, providing us with unparalleled consistency.

Once the rider is prepared to conduct a test, they will conduct multiple out-and-back 800 [m] sections using the same equipment, body position, and race pace power level. This provides direct measurement of rider variance from test to test (including effects of the unsteady wind and environmental conditions) and provides a converged, average aerodynamic drag value with a measured level of confidence. This represents a baseline configuration from which all other equipment changes can be compared. For the current testing, AeroLab sensors found a baseline CdA (aerodynamic drag area) of 0.4313, with a confidence of ±0.0006. This is a measurement of the rider efficiency moving through the air. For comparison, a competitive professional time trial cyclist often achieves a CdA less than 0.2000. Since CdA is directly (linearly) proportional to the power required to overcome aerodynamic drag, achieving, for example, a 3% decrease in the athletes CdA directly corresponds to a 3% decrease in the power required to overcome the aerodynamic drag they are facing.

Once the rider baseline configuration is complete, the rider can try out any new piece of equipment, body position, skin suit, helmet, etc., conduct the same number of out-and-back 800 [m] sections, and determine if the newly selected equipment is aerodynamically "more efficient" than the baseline configuration.

When conducting these tests, the coach/fitter/rider must take care in understanding the effects of tire pressure and temperature on rolling resistance (which is a secondary but often overlooked aspect of rider efficiency).

Man riding a Fat bike in cold  weather
Lea Davison

The Fastest Suit for a Mountain Biker

With Lea, we tested different fabrics, sleeve lengths, and zipper locations. The table below outlines the savings of the “winner suit” at various speeds. The Table directly computes the time savings for a 40 [km] time trial relative to the baseline configuration for: (i) a realistic 250 [W] effort level on a flat course, (ii) a fixed speed of 20 [kph], (iii) a fixed speed of 40 [kph]. What is enlightening from this comparison of time savings is that at lower speeds, the time savings increases in an absolute sense since the total duration of the 40km TT is extended. It is important to recognize the time savings which can be gained even at lower speeds of a mountain biker!

Realistic 250 [W] effort level on a flat course

 

 

CdA

Crr

Power [W]

Speed [kph]

40km TT Time

Time Saved

Baseline

0.4313

0.0065

250

31.17

77m 0s

-

Winning Suit

0.4274

0.0065

250

31.25

76m 48.4s

11.6s

 

Fixed speed of 20 [kph]

 

 

CdA

Crr

Power [W]

Speed [kph]

40km TT Time

Time Saved

Baseline

0.4313

0.0065

102.3

20.00

120m 0s

-

Winning Suit

0.4274

0.0065

102.3

20.04

119m 45.5s

14.5s

 

Fixed speed of 40 [kph]

 

 

CdA

Crr

Power [W]

Speed [kph]

40km TT Time

Time Saved

Baseline

0.4313

0.0065

448.7

40.00

60m 0s

-

Winning Suit

0.4274

0.0065

448.7

40.11

59m 50.3s

9.7s


If we ignore the effects of wind shear which are unknown and course dependent on uphills and downhills, then we are essentially considering the influence of speed on the savings. As shown in the above tables, there are different ways to consider the savings. The savings will be course dependent. One method of calculating the overall effects of uphills and downhills on a course performance is to run a simulation of the course (with a known elevation profile and known or assumed wind conditions). AeroLab sensors can be used in conjunction with a course simulation for accurate estimation of finishing times and overall savings.


"Working with Garneau has been revolutionary for my cycling career. I can bring them any feedback or ideas, and we immediately get to working on making things better. I was discussing with Garneau this spring before the season started on the aerodynamics of certain products and if aerodynamics even made a difference at the oftentimes lower speeds in mountain biking. In true Garneau style, we immediately set out to answer the following question: "Could an aero Garneau skin suit give me an edge over my competition?" We collaborated with Aerolab and used some of their new technology to conduct an aerodynamic test that had never really been done before, and the results were exciting. Skin suit aerodynamics do, in fact, make a difference in performance on the mountain bike. Garneau then created for me a custom aerodynamic skin suit that gives me a boost in confidence and speed every single time I put it on. For the highly competitive and tight racing in the women's world cup field, this skin suit can actually make the difference between a phenomenal top 10 performance or just barely missing the mark. In a race, I know I am using less wattage to go the same speed, and this fact alone is a game changer. Thank you Garneau for helping me achieve my goals." 

– Lea Davison

Man riding a Fat bike in cold  weather
Lea Davison