LOTUS 110 Wind tunnel test
The goal of this test was to evaluate the aerodynamic performance of iconic bikes such as the Lotus 110 and Zipp 3001 against a modern frame - the Cervelo P5.
LOTUS 110
One of our team riders Dan is the proud owner of a Lotus 110, and has done exceptionally fast times on it in the past!
This particular frame has been custom painted in gloss white, with a custom seatpost clamp manufactured to achieve the saddle height required. A Tririg Omega front brake and cable was installed as well as a rear brake.
ZIPP 3001
This Zipp 3001 has been ridden by a number of AeroCoach team riders, including director Dr Xavier Disley and Alex, the test rider for this experiment. Both have held their 10 mile personal bests on it in the past!
The forks were swapped out to an aero Kinesis aluminium model, rather than the round tubed fork legs specced on the 1996 bikes.
CERVELO P5-6
This particular Cervelo P5-6 was previously owned by Ironman triathlon superstar Frederik Van Lierde. It has integrated brakes front and back as well as handlebars designed specifically for the frame.
We chose the Cervelo P5-6 to compared against, as having completed countless hours of testing over many years we know it's one of the fastest frames on the market.
We tested three bikes in the wind tunnel, with a pedalling rider and spinning wheels at 45kph. In order to just test the difference between frames, we set the position of each bike up identically, and used identical components wherever possible.
All the bikes were set up 1x with an AeroCoach ARC chainring, AeroCoach AEOX wheels and 3T aerobars. A Cervelo P5-6 model comes equipped with 3T Aduro bars, and we used the (UCI illegal!) 3T Ventus bars on the Lotus 110 and the Zipp 3001.
We tested the aerodynamics of the bikes at our standard test speed of 45kph. This allows us to get good clean data (compared with testing at lower speeds, where the resolution isn't as good) which can then be applied to lower speed calculations later. As an example, a 10w aerodynamic drag saving at 45kph is equivalent to 4.7w at 35kph.
Our test rider was Alex, a time triallist from the AeroCoach team. Alex raced on the Zipp 3001 for a number of years, but also enjoys a TT on a road bike to mix things up!
Alex is an experienced racer and has completed aero test sessions with us before, so was used to staying consistent on the bike, ensuring that the data was as accurate as possible.
We completed multiple repeats over a range of different yaw angles to give as complete an overview of the performance of each bike as possible.
Results from the wind tunnel test between the three bikes are shown below.
When interpreting wind tunnel results it is important to understand yaw angle weighting.
Real world cycling is affected by changes in wind speed and direction.
The angle of attack of the wind on the cyclist is referred to as “yaw angle”, and this is affected by four components - rider speed/direction as well as the wind speed/direction.
While cycling on the road, you will experience a range of yaw angles. Very high yaw angles are much less common than lower yaw angles, and this can be expressed as a weighting function - for example at 45kph you spend ~80% of your time at 7.5deg yaw or less. At <40kph this extends out to 10deg, and at >50kph you will see 5deg or less.
From this data set we can see that the Cervelo P5-6 is consistently faster than the Lotus 100 and the Zipp 3001, at all yaw angles.
The Zipp performs particularly well at 0deg yaw: this is likely due to the incredibly narrow (28mm!) head tube.
Once the yaw angle increases the shape of the Lotus creates a larger difference in aerodynamic drag between that and the Zipp.
Using a yaw weighting function, to provide an overview of the aerodynamic performance during typical outdoor wind conditions, at 45kph the Cervélo P5 was the fastest, followed by the Lotus 110 (4.4w slower) and the Zipp 3001 (4.9w slower).
Compared with one of the fastest frames on the market, some of the older bike designs are still race worthy, providing less than a 5w aerodynamic drag penalty at 45kph!
As the global cycling and triathlon market continues to innovate, the question remains whether 25 years into the future we will see a similar kind of improvement, and how regulations and new technologies influence frame design and manufacture.
