It was within the Tour de France in 2016 when Chris Froome shocked audiences not along with his moped-like accelerations or his notorious oscillating using fashion, however his unimaginable new descending method.
For individuals who have not seen it, it consisted of sitting on the highest tube, along with his physique hugging his stem, but nonetheless in some way pedalling. It makes a stark distinction to the positions of yesteryear – as an illustration Marco Pantani’s iconic over-the-rear-wheel cougar-like descending fashion.
We questioned precisely how a lot distinction time has made, and whether or not with ‘marginal positive factors’ knowledge Froome is certainly a step forward of Il Pirata. So we determined there was just one solution to discover out (with out pitting ourselves towards a steep incline and a demise want).
The type people on the Boardman Efficiency Centre have been up for the problem, and so we headed to Evesham, Worcestershire to place all number of positions to the take a look at, and see which was quickest.
We start by measuring drag on a really primary place on the drops. For this, I sit comparatively upright, ready that I might trip on a standard flat stretch whereas pedalling, slightly than one the place I’m at a velocity the place I might be aiming to chop as a lot drag as I presumably can and cease pedalling.
For each run we measure my coefficient of drag space (CdA), which determines how a lot drag my place will generate at completely different speeds.
For this primary one I rating 0.295, which implies that to achieve 35kmh I have to generate 208 watts of energy, on the flat.
On the drops
Our first true descending place is a straightforward tuck on the drops, with my arms over the brakes.
On this place I scored a CdA of 0.1993, an enormous drop in drag. Because the wind tunnel doesn’t generate downhill pressure, we nonetheless use a calculation of the wattage wanted to achieve 35kmh as a indicator of the effectivity of a place, primarily based on CdA.
At this drag, I might solely want 154 watts of energy to journey the identical velocity. However that is removed from the quickest place.
Sitting on the highest tube just isn’t a snug place, and I struggled to carry this for greater than 30 seconds. Froome manages to pedal whereas on this posture, which would definitely take some observe.
The Froome place is clearly a well-calculated one, as I noticed my CdA drop all the way down to 0.1718. That noticed my 35kmh energy drop all the way down to 139 watts – making this place a full 69 watts quicker than my baseline place.
At a really tough calculation, if I added that wattage to my watts at a velocity of 35kmh, that might see me travelling round 5kmh quicker with no further effort. The acquire can be proportionally extra at at the next velocity.
There are some disadvantages, although. Whereas Froome’s place lowers the centre of gravity, it additionally places the burden largely over the entrance wheel, which may change dealing with traits and probably make the bike rather less secure. He’s clearly nailed it, however us lesser mortals had higher be cautious.
Pantani’s place has really been consigned to historical past, with solely essentially the most obscure of present execs ever making an attempt something prefer it. Wanting on the information, it could be clear why.
The Pantani place gave me a CdA 0.1947, which was solely very barely quicker than my tuck on the hoods. That’s a acquire of only one watt (though 55w quicker than a standard biking place), but offers up the power to pedal whereas descending.
Maybe, although, Pantani knew very nicely that weight over the again wheel can assist general stability, and his place was extra about getting the proper place on the highway slightly than the proper place towards the wind.
We have been unable to essentially seize the spirit of Graham Obree’s Previous Devoted using fashion, however it appeared a becoming title for a place that tries to place the again as flat as doable.
Because it occurs, that is my common descending place when the highway is straight and there is not any probability of obstacles that require sudden braking.
With regards to approaching a nook, or any unsure territory, the arms should return to cowl the brakes.
So, what are the positive factors? Nicely, fairly good. My CdA was recorded at 0.1679, a really slippery rating and the quickest of all of our runs.
The facility wanted to journey at 35kmh was simply 137 watts.
The place affords a low centre of gravity, and good stability with weight properly distributed front-to-back, however the lack of management over the drops is a giant sacrifice, and anybody making an attempt it must be very assured in dealing with.
So what can we conclude that the ‘Obree’ is the quickest place in all circumstances? Nicely no.
Everyone seems to be a unique form, and so what’s quickest for me will not be fast in any respect for somebody with narrower shoulders, narrower handlebars, an extended physique, a shorter neck, roughly weight, a decrease using place…
Then there’s the truth that we solely examined a single yaw angle, the angle at which the wind hits the rider. That angle was 0°, whereas extra generally a rider will expertise a spread of 0-15° yaw.
As with a lot of aerodynamics, the complexities of the science imply that it is laborious to extrapolate a lot, or to make any laborious and quick guidelines.
In the event you actually need to know what’s quickest for you, nothing beats a visit to the wind tunnel.
Many due to the Boardman Perfomance Centre for conducting our take a look at. Click on right here for more information on the aerodynamic testing on the centre