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Froome’s descending position isn’t as aero as Sagan’s

How to get super-aero on the descents while staying safe

Chris Froome’s curious descending position isn’t as aerodynamically efficient as he might hope, according to new research from the Netherlands and Belgium. 

Researchers led by Bert Blocken of the Eindhoven University of Technology in the Netherlands and KU Leuven (Leuven University) in Belgium investigated the aerodynamic performance of different descending positions in cycling, looking particularly at the positions of Chris Froome, the late Marco Pantani, Fabian Cancellara, Peter Sagan and two different positions adopted by Vincenzo Nibali.

Let’s cut to the chase here: Peter Sagan’s position – sitting down on the top tube, but pushed further back than Chris Froome’s position – comes out on top, based on the assumption that none of the cyclists in these positions would be pedalling, or they’d all be pedalling with the same power output.

Here are the results in full:

Bert Blocken, Eindhoven University of Technology, the Netherlands and KU Leuven, Belgium - 1.jpg

Pic courtesy of Bert Blocken, Eindhoven University of Technology, the Netherlands and KU Leuven, Belgium

Fabian Cancellara’s ‘back upwards’ position came out slowest with Nibali’s ‘back horizontal’ position 8% faster. Froome’s position was 9% faster than Cancellara’s, Nibali’s ‘back down’ position was 12% faster, while Pantani’s position, resting his chest on the saddle with his bum just over the back wheel, was 14% faster.

Sagan’s ‘top tube safe’ position, sitting on the top tube with his chest on the stem so that his weight is distributed quite evenly over the wheels, was calculated to be 17% faster than Cancellara’s.

How did Professor Blocken and his team work this out? 

First, through wind-tunnel testing. They scanned a cyclist in different positions, had models made at 1:4 scale and tested those models in the wind tunnel in Liège.

Check out the full paper for details on the testing methods. 

Then the team used computational fluid dynamics (CFD) simulations with extremely high-resolution models (36 million calculation cells).

The researchers acknowledge that it’s a crude calculation but say that Sagan’s ‘top tube safe’ position could have saved Froome 1:07mins over the position he actually used when he attacked on the Peyresourde descent on Stage 8 of last year’s Tour de France (he might not care; he won the race anyway). As well as being faster, the researchers believe that the top tube safe’ position is less risky – hence the name, obviously!

Froome’s position does have an advantage over the ‘top tube safe’ position in that it allows pedalling but not, the researchers say, with a large power output.

Superman 2.png

Interestingly, the so-called ‘Superman’ position (above), where a rider essentially lies forward on the bike with his torso on the saddle and legs stretched out behind him/her (not to be confused with Graeme Obree’s Superman position which was entirely different), was found to be 24% faster than Cancellara’s base time… But if you want to ride down the Peyresourde like that, well, you’re on your own.

For more info read the paper in full here.

As an aside, Peter Sagan Tweeted today that he was working on his aero position in California, so you can expect to see it making another appearance in one of the big races soon.

 

Mat has been in cycling media since 1996, on titles including BikeRadar, Total Bike, Total Mountain Bike, What Mountain Bike and Mountain Biking UK, and he has been editor of 220 Triathlon and Cycling Plus. Mat has been road.cc technical editor for over a decade, testing bikes, fettling the latest kit, and trying out the most up-to-the-minute clothing. We send him off around the world to get all the news from launches and shows too. He has won his category in Ironman UK 70.3 and finished on the podium in both marathons he has run. Mat is a Cambridge graduate who did a post-grad in magazine journalism, and he is a winner of the Cycling Media Award for Specialist Online Writer. Now over 50, he's riding road and gravel bikes most days for fun and fitness rather than training for competitions.

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19 comments

Avatar
Carton | 6 years ago
0 likes

Everyone who cycles for fun should do what's fun for them. And it also depends on terrain, -2% and -10% are very different kettles of fish.

But, personally, 90% of the time I'm just coasting on descents, pretty much bolt upright, actually using my torso as a wind brake into corners. I'm still faster than the vast majority of my fellow punters on the local descents, even on my mountain bike. And it provides a bit of a physical an mental break.

I think for most people who want to go fast on anything even midly serious, getting the cornering right is significantly more important and enjoyable than railling the flats. Brake, press your foot on the outside pedal, kick as you're tracking out. Not rocket science. Fun, for me. More fun than figuring out which tuck feels faster.

Well, on most days. Sometimes I just want to spin out my compact and dive (almost, but not quite on, my top tube). The former is a lot harder than most make it out be, but that's a matter for another day.  The latter surprisingly effective, as the rocket science seems to say.

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alansmurphy | 6 years ago
0 likes

Indeed, that one must have come thru as I was typing and the hamster spins the wheel of internet...

 

 

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alansmurphy | 6 years ago
1 like

I disagree Dotti - did the Tour Of The Peaks on Sunday... 10 miles up to start with followed by Winnats Pass and the Cat and Fiddle. Plenty of 35+mph descents where there was no point pedalling as you can save your legs for the climbs!

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dottigirl replied to alansmurphy | 6 years ago
0 likes
alansmurphy wrote:

I disagree Dotti - did the Tour Of The Peaks on Sunday... 10 miles up to start with followed by Winnats Pass and the Cat and Fiddle. Plenty of 35+mph descents where there was no point pedalling as you can save your legs for the climbs!

Ummm, I did include conserving/saving energy as one of the caveats.cool

Avatar
tritecommentbot | 6 years ago
2 likes

Right got it.

Nobody should ever coast unless they're Froome or Sagan. 

Only on the internet crying

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dottigirl replied to tritecommentbot | 6 years ago
0 likes
unconstituted wrote:

Right got it.

Nobody should ever coast unless they're Froome or Sagan. 

Only on the internet crying

Or have run out of gears.

Or are desperate to save energy.

Or are simply not in a rush to get anywhere.

enlightened

They should definitely not get into a ludicrous descending position.

Unless they're testing out said position at slower, less risky speeds in training. (I'm thinking you really don't want to try a new position when going at the fastest speed possible.)

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surly_by_name | 6 years ago
0 likes

My experience is the Sagan feels a lot less sketchy than the Froome as latter leaves a lot of weight over front wheel (which leaves me in fear of being catapulted over bars). I don't have courage to stick to the full Sagan when it's gets a bit twisty, which sees me having to manouevre out from underneath nose of saddle back onto saddle to adopt the Back Down or Back Horizontal position. I suspect this maneouvring causes a signficant aero loss to the point where I don't imagine there's a net benefit to me of getting down into the Sagan. 

I wouldn't recommend the position Pantani on a twisty descent, unweighting the front wheel like that will have a major effect on handling.

Also, in the back down/back horizontal, I think the pro look is to put your hands on the tops and pull your elbows in rather than holding on to the drops. Obviously not so good for braking.

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tritecommentbot | 6 years ago
3 likes

I'm reading this as you being triggered by some dude with better looking legs who was outskilling you on the downhill, so you had to put power down to get past him when he was coasting.

 

crying

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SingleSpeed replied to tritecommentbot | 6 years ago
0 likes
unconstituted wrote:

I'm reading this as you being triggered by some dude with better looking legs who was outskilling you on the downhill, so you had to put power down to get past him when he was coasting.

 

crying

 

Then you're reading it wrong  1

Avatar
dottigirl replied to tritecommentbot | 6 years ago
0 likes
unconstituted wrote:

I'm reading this as you being triggered by some dude with better looking legs who was outskilling you on the downhill, so you had to put power down to get past him when he was coasting.

crying 

coolIf you can still pedal and you're not spun out, you have no business coasting, never mind getting into an extreme descending position.

Unless you're Sagan/Froome/etc. Or so desperate to conserve energy that you'd sacrifice speed.

(Of course, there is also the possibility that Surly EDIT: SingleSpeed had more gearing than the other guy, who may have spun out.)

EDIT2: oops, forgot that my post would drop down and now it doesn't make sense...

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SingleSpeed replied to dottigirl | 6 years ago
1 like
dottigirl wrote:

 

coolIf you can still pedal and you're not spun out, you have no business coasting, never mind getting into an extreme descending position.

 

 

 

My Point exactly, hence taking the piss by overtaking him sat on the hoods.

 

 

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SingleSpeed | 6 years ago
0 likes

I was doing a sportive in Spain chilling out descending somewhere near the pyrenees and some Euro tanned-shaven legged type comes past sat on the top-tube.

I couldn't resist but start pedalling and over take him sat bolt upright on the hoods, he muttered something but I didn't get it as it was in some foreign tongue.

 

...I normally descend in the "12% Position" not being on the saddle feels sketchy as hell to me. 

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RobD | 6 years ago
0 likes

I love that so much effort has gone into studying it (not just this study but all of the others) if he used it on every descent then it might have been more of an issue, but I think the fact he only broke it out for that stage (and still won) makes it a little bit of a moot point. Also, does the rider's body size make a difference? Froome is a lot more gangly than Sagan, not sure if the positions would be more suitable for different rider types. 

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BehindTheBikesheds | 6 years ago
0 likes

The Pantani position gives more control IMHO through tighter bends/corners than the 'Froome' or the top tube safe, I use the Pantani position for when I need to really slam on the anchors as this improves weight distribution (as oft used in MTB) so back wheel braking is improved a smidge.

For going down descents I'm deffo a back down guy, it works for me even on the shopping bike down the local 1/4 mile long 6%er to tesco (37-38mph cos it's facking bumpy as near the bottom), not sure I could or even want to do the top tube safe (sic) position.

Froome could likely have adopted a slightly better position to allow him to put more power down when pedalling and sacrifice a little aero but ATEOTD it was the unexpectedness and commitment of it that did the job.

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Sven Van Anders | 6 years ago
1 like

Pantani's descending was a joy to behold.

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joules1975 | 6 years ago
1 like

The position may not be the most aero, but I guess it's make pedalling easier compared with 'Top Tube Safe' or 'Pantani', and not as neck agony inducing as 'Back Down'.

The result is that he can probably go faster than the other option when in his position because he can keep pedalling and he can stay in the position for longer because he's not straining his neck as much.

I still don't want to try it though!

Avatar
Mat Brett replied to joules1975 | 6 years ago
7 likes

joules1975 wrote:

The position may not be the most aero, but I guess it's make pedalling easier compared with 'Top Tube Safe' or 'Pantani', and not as neck agony inducing as 'Back Down'.

The result is that he can probably go faster than the other option when in his position because he can keep pedalling and he can stay in the position for longer because he's not straining his neck as much.

I still don't want to try it though!

Agree with all of that, but if he ever wants to win BBC Sports Personality of the Year he needs to go full Superman coming down Galibier and he'll be a shoe in.

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Rapha Nadal | 6 years ago
0 likes

I'm sure he'll get over it.

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DaveE128 | 6 years ago
2 likes

I suspect that part of the value of Froome's descending position was psychological - it was a bonkers move that no-one expected, worked very well, and took away any notion of predictability.

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