Clip on aerobars

We tested 6 positions in total: 

RELAXED ARMS HOODS (baseline)

The baseline and reference position was holding the hoods, with slightly bent elbows. This is a typical comfortable position that can be held for long distances.

TOPS

This is a climbing position with hands holding the tops of the bars either side of the stem

DROPS

Holding the drops helps reduce torso angle, which is often more aerodynamic on a road bike, and is useful to lower the centre of gravity when cornering or descending.

AERO HOODS

This is similar to the hoods position but with forearms parallel to the ground. Popular for breakaway riding it helps to lower your torso angle and also present less forearm to the wind compared with the drops position.

ASCALON AEROBARS

Ascalon extensions were mounted to the handlebar to give a low torso, narrow arm position just like on a time trial bike. 

ASCALON HOODS

In order to examine the aerodynamic impact of mounting extra aerobars on the bike but not using them, we used a relaxed hoods position as a comparison to baseline.

In order to test aerodynamic drag we went to an outdoor velodrome, and our test rider Malachi performed a series of repeats of each position using a power meter, whilst we also measured environmental variables such as wind and air density.

Malachi was wearing bibs and jersey, aero gloves and socks, an aero road helmet and he was riding a Specialized Allez Sprint.

The data was  processed as in our commercial outdoor aero sessions, using custom scripts to establish a CdA (aerodynamic drag) for each position.

CdA is the combination of both frontal area (the A part of the equation) and drag coefficient (Cd), and is reported in m².

The CdAs and power output differences for each of the positions tested can be seen below.

As we've found in previous tests, holding an "aero hoods" position with your forearms parallel is an excellent method of improving your aerodynamics, saving over 40w at 40kph compared with an upright hoods position.

Swapping to clip on extensions was another 17w faster than this however, but much more comfortable and easier to hold as the aero hoods position is very fatiguing on the upper arms. Converting the power savings to a speed saving would take your average speed from 40kph in a relaxed hoods position to 43.3kph in the aerobars for the same power output!

We also tested the impact of having the aerobars on the front of the bike in clean airflow when you're not using them, which was a 9w penalty. Meaning that if you've mounted clip on aerobars on your bike you should use them as much as you can!

In this test we found that using clip on aerobars allowed Malachi to improve his CdA to a value better than he could achieve on drop handlebars, no matter which position he tried to hold on the drop handlebars. 

Using clip on aerobars is a great way to achieve a sustainable aero position on a road bike, if you're taking part in a time trial or triathlon and you don't have a full time trial/tri setup. Holding an aero hoods position is also a large advantage, but is much harder to maintain.