Aero-Aware

LeMond1990

Bike racers have been aware of the advantages aerodynamics gave them for decades, perhaps from the very beginning of competitive cycling itself. Up until the 1989 Tour de France, nothing had made the differences more stark, than a colourful mix of imagery, marketing & race winning choices, to propel Greg LeMond to an 8 second advantage, turning around a 50 second deficit & winning the Tour de France on the final Paris time trial stage. Things have never been the same since, it set the scene for the public’s awareness of the importance of aerodynamics in cycling, which is still influencing professional racers, club riders, sportive riders & marketing departments to this day.

80’s to 90’s

Up until the 80’s, it was perhaps the UK time trialing scene that you could have looked to for some extreme examples of bicycle aerodynamics, Rouleur recently ran a story on Alf Engers & his realisation that drilling holes in everything actually made him slower (Rouleur issue 62: Drillium). Aerodynamics had been progressing right through the 1980’s, silk jerseys for time trials were replaced with full lycra skinsuits, we had carbon disc wheels, and we had Francesco Moser, pushing the limits with radical bike designs & wind tunnel testing (amongst some other stuff). Moser2These changes could all be considered ‘marginal’, the position was still relatively the same, just finer tuned with the help of technology. Once we got to the end of the 80’s, LeMond started working with Boone Lennon from Scott USA in developing a position using an innovation from triathlon (there’s also an argument it was first used in 1984 in the RAAM). The advantage this new arm, shoulder & body position, allowed by the use of tri-bars provided a ‘step-change’ in aerodynamics, almost overnight in cycling terms, this wasn’t a ‘marginal gain’, it was a Tour winning gain. The advantage of containing the arms within the frontal area of the body was so large that within a few months almost everybody was using the new position in the pro peloton, even Sean Kelly, still riding toe straps until the bitter end, took it up relatively quickly.

Wind Tunnels

The factor which multiplied the gains from the 80’s onwards was wind tunnel testing. Although the emerging aeronautical industry had been using these since the late 1800’s, their commercial availability & cost were out of reach for sports people, especially cycling, which had traditionally been poorly funded & relied on internal sponsors (i.e. bike manufacturers) to fund most of the top teams until a few decades ago.

As we now know, small changes can make all the difference, with the advent of wind tunnels cars completely changed shape & pro riders could now quantify every single change in equipment, components, position & clothing material, if they had sufficient funding. This introduced a new aspect to pro cycling, but wind tunnel time was expensive, so teams with bigger budgets could now use their cash to outperform their rivals, with very significant gains being made in this early period, compared to the current marginal gains we hear about in todays peloton. This was a game changer, 1989 shook the teams who hadn’t embraced the change, or hadn’t realised what could be achieved. We still saw riders with their jerseys flapping in the wind, you won’t see that now in your local race such is the level of knowledge available now.

Greg LeMond V Past & Present

1986-tdf-19-Lemond

A rider at the top of his game (for the 2nd time) during this transition period of aerodynamics was Greg LeMond, he was also the most prominent rider embracing it in the pro peloton, but he wasn’t the only one. If we look at how his position & the technology he used developed we can see the innovations that appeared in greater detail. The photo above is from 1986, differing from todays TT setup, note the shallow front rim profile, drop handlebars on standard road frame, no shoe covers, non protective aero shell helmet & more importantly, the lack of tri-bars. On the other hand, the skin suit looks as fitted as todays, but lacking the longer legs & sleeves we see in todays peloton.

Fignon-FrontLemond-Front

Embed from Getty ImagesLemond_89_TT

The contrast displayed in the 1989 photos above, of LeMond’s tucked position, his arms in line with his legs & an aero helmet (which we now know is much faster than a bare head), to Laurent Fignon’s more classic time trial style marks a turning point in position, a stark contrast between the old & the new. It also marks the beginning of pro riders not just looking for small advantages in equipment & clothing, it marks the realisation that technology could provide huge gains over your rivals, not just refinements. Also note that LeMond’s skin suit has grown longer sleeves ahead of its time, which is standard now, as we know lycra is more resistant to drag than skin. Fignon’s position looks very similar to Lemond in 1986, but he’s perhaps gone for a front disc in desperation rather than common sense, while it may work in a windless velodrome, it may have cost him energy outdoors fighting any crosswinds, as we saw him “bouncing of the barriers” in the final 200m.

For comparison, just look at the image below of Tom Dumoulin in his aero position on a modern time trial bike. His position is further refined, rotating his body around the bottom bracket while maintianing hip-torso angle & therefore power development. Dumoulin’s helmet seems profiled to be in line with his back, LeMond’s was a last-minute UCI approved shortened (hacksaw presumably) version of a Giro triathlon helmet. Unlike LeMond in ’89, Dumoulin has a deep section front wheel with carbon spokes & an aerodynamic frame (and forks) with every tube profiled to the limit of the UCI rules (LeMond’s was more or less round tubing, apart from some added fillets). We also have minimal brake levers & various other details that all shave off watts, the big similarity remains the use of tri-bars.

Embed from Getty Images

The Gist Of It

Stage 21 of the 1989 Tour was by no means the first time aerodynamics was considered of prime importance, but it was the event that caught the imagination & made ‘aero’ position & equipment just as important as training.

Just consider if the 1989 final stage had been a sprint into Paris rather than a time trial, if this event had not taken place in the spotlight of the world, how different would pro cycling look today? Would the UCI have rapidly banned ‘tri-bars’ without the drama & revenue generated from a thrilling end to the Tour to preserve the look of the machine to the Merckx era, as with their Hour Record rule changes. In UK cycling, would ‘that Lotus bike’ have existed, would Obree & Boardman have been able to use their innovations & skills on the world stage? Would the various people & technology that combined to create the advances that allowed British Cycling to rapidly ride to international track winners, and the subsequent influx of riders being provided a living while rising to the higher echelons or world road cycling, like Wiggins & Armitstead?

This defining event in 1989 opened all sorts of opportunities in cycling, ‘aero’ had been done many times before, but not displayed previously in such an establishment shocking manner. Development in cycling aerodynamics had been a slow boil most likely due to tradition, significant gains had been made, this blatant new position could not be ignored, it was the catalyst for others to look further & see what could be achieved. The results are now evident in your local bike shop.

(Note: All non-Getty images were identified as having a ‘Creative Commons’ licence on Google image search & Flickr.)

Giro Air Attack Data

I found some information regarding some of the daft helmets in my previous post HERE. Getting power outputs from this requires a small amount of schoolboy maths, so here it is for one of the silly looking helmets on the market.

The maths

Giro have published their drag in Newtons (N) on their website, you can get to it through the following link. Giro Air Attack, then looking at the COMPARE tab. this shows you the difference between the new Air Attack & the established vented Aeon helmets, which is reasonably aerodynamic looking in itself. But if this data is accurate it should give us a good estimate of the power saving that Giro sponsored teams get by using the Air Attack over a standard Giro vented helmet.

The figures are at 25mph or 40kmh, the Aeon has a drag of about 4.2N, the Air Attack approx 3.7N. The drag will increase significantly as speed increases, this isn’t linear, so going twice the speed produces much more drag than a multiple of two, here’s the figures.

25mph/40kmh

Aeon: Power requirement is Force X Velocity. 4.2 (N) X 11.176 (m/s) = 46.9 Watts

Air Attack: Power requirement is Force X Velocity. 3.7 (N) X 11.176 (m/s) = 41.4 Watts

So we see that at 40kmh, our pro riders are saving approx 5 Watts of power by wearing a silly hat. Now lets look at what happens when we consider sprint leadouts & other high speed situations at 80kmh.

50mph/80kmh

We are not given the drag forces at this speed, so we’ll have to do a calculation to determine CdA, which is the coefficient of drag X area, we just need the value so it can be approximated by using the 25mph figures as follows.

F = CdA X p X (v squared / 2)

F = Force i.e. our drag value in Newtons.

CdA = Drag coefficient X area

p = Air density in kg/m3

v = Velocity in m/s

At 25mph we have F, p (normally approx 1.225 at sea level) & v (25mph is 11.176m/s). So to save you a headache, I’ve calculated CdA as the following.

CdA Aeon = 0.0549

CdA Air Attack = 0.0484

So using the same formula we can alter the speed and we now find that the drag on each helmet is as follows:

Aeon:

Drag = 16.6 N

Wattage required = 16.6 (N) X 22.222 (m/s) = 369 Watts

Air Attack:

Drag = 14.6 N

Wattage required = 14.6 (N) X 22.222 (m/s) = 325 Watts

Conclusion

We can see from the above that power requirement is huge at 80kmh compared to half that speed, approximate savings at the lower speed are about 5 Watts, while at the higher speed we see about 44 Watts. We can assume that most sprinters & lead out men require over 1500 Watts. The above calculations are solely for the helmet, not the total power requirement, so we can see how a series of so-called ‘marginal gains’ will produce a few watts here, a few watts there and you see why the sprinters & lead out men are using any aero benefit they can to deliver their sprinter to the front at as high a speed as possible. Also bear in mind that these are all estimates, but likely not particularly far away from the actual wattage savings. As I said before, silly hats are here to stay, in fact they may get even sillier until the UCI steps in.

Breaking Wind

I’m often irritated by reading some very uninformed & aggressive forum trolls ideas on what makes riders fast in a time trial, the bit that bothers me most is the complete lack of understanding of aerodynamic theory. This isn’t too hard to grasp, at it’s most basic, something small creates less drag, while something big creates more. But it gets complicated when we start looking at cross-sectional area & body lengths, here’s some busted myths…

I don’t go fast enough to use any aero kit.

Aye you do, even if you’re ground speed is low, you most likely race in winds blowing faster than you can ride, so you’re combined air speed is at a significant level where small aero advantages will make a big difference. It’s all too often you see riders off their aero bars while riding into a headwind, this is the worst thing you can do, this is precisely the point that you need to be the most aerodynamic, regardless of your overall average speed.

Get aero in a headwind, think about air speed rather than road speed for aerodynamics.

Why are pro riders going faster in time trials when they lose weight?

It’s not hard to understand, a smaller object requires less power to travel through air at the same speed as a larger object. A larger object has more wind resistance. So if we take one ‘sample rider’ weighing 80kg, then reduce his weight to 75kg, will he be faster on the flat? The answer is undoubtably yes. But you’re now thinking that it only counts if a rider reduces that weight as fat content, incorrect. The rider can reduce the weight as a mixture of fat & muscle, making their limb & torso cross sections smaller, while not reducing their overall fat percentage, here’s how.

Lets say this ‘sample rider’ is pushing 400 watts during a time trial at 80kg, 400W isn’t too much in muscular terms, but it’s a lot in aerobic terms. Your average skinny youth rider is perfectly capable of producing a wattage much greater than this in a sprint, so that in itself displays the required muscular physique to produce over 400W. So if our ‘sample rider’ reduces their weight to 75kg (for example if they were already at a very low body fat percentage), then they have lost 5kg but still have plenty of muscular power left to produce the required wattage.

Aerobic power output does not require big muscles, smaller muscles have less drag, an endurance rider can lose muscle and still go just as fast aerobically. Similarly, if you’re a chubby cyclist, you could record some much better results from eating less cakes & drinking less lemonade.

If I go as low as possible, I’ll be quicker?

Also not true.  As the hip to torso angle decreases, so does power generated, so a rider who’s front end is crouched as low as possible is losing power in that position. This results in a play off between power & aerodynamics, something that is going to be very hard to replicate unless you have access to the measurement resources of a pro rider, so you’re going to have to estimate it yourself. There’s also going to be physical limitations here, Jonathan Vaughters has said that his pro rider, Dan Martin, has bad hip flexion, so will be unable to attain a very aerodynamic time trial position, potentially ruling him out of winning grand tours with a large amount of time trialling in the future. There’s also the physical limitations involved here, get too low and your thighs will start to hit your ribcage. It’s all about finding a ‘sweet spot’ that is correct for you as an individual, a compromise between aerodynamics & power generation.

Low isn’t always best, everybody is different, so it’ll take a bit of work for each person to find their optimum position, don’t try to copy somebody else exactly, but certainly take some tips from photo’s & videos of pro’s with a similar body type to yourself who have access to wind tunnels.

I can go just as fast as somebody else who weighs the same as me with the same power output.

Maybe you can & maybe you can’t, some things are just down to genetics. If you are the same weight & height as somebody else, but possess a longer back & shorter legs, you may have a lower aerodynamic drag. A simple rule is that longer objects along the direction of movement through air cause less turbulence, so a rider with a long body like Wiggins for example has a genetic aerodynamic advantage, he has short arms relative to his size and can also tuck those away easier as everybody has to conform to the UCI positional rules which advantage & disadvantage certain body types. So if you have access to a power meter, you may be able to find your optimum position by doing some field testing, but it has to be very closely controlled, likely impossible to do the estimates on different days, or even different conditions on the same day, a very subjective & complicated area to step into.

A time-trial bike is quicker than a road bike.

Again, this statement isn’t true in itself. The statement should be, ‘a correct position on a time trial bike is faster than a correct position on drop bars.’ I’ve been really shocked by the awful positions of some riders on tri-bars from early season Scottish race photos, some actually assuming worse positions on tri-bars than holding the tops of the bars, yet they assume they are ‘aero’ as they are using aero kit. What people forget is that aero kit in itself isn’t aerodynamic as such, it is used as a tool to get YOU more aerodynamic. You can spend all the money you like and bolt on all sorts of stuff, but without some thought & correct positioning, you could be better off without it.

Spend some time to get your position correct, don’t just bolt on kit & hope for the best.

A constant heart rate gives the fastest time.

As far as heart rate goes, it’s a historic measurement, it measures the effect on your body of what you did to it a few minutes ago, so in short time trials it is virtually useless for the first few minutes until you reach a plateau. At that point, if you encounter a headwind and you maintain the same speed, your heart rate monitor will tell you all about it, just a bit too late. Another effect is something called cardiac-drift, where your heart rate rises over time with a constant power output, so if you maintain a constant heart rate over a time trial, your will be producing less & less wattage as time goes on.

Heart rate isn’t an ideal guide to riding a time trial, but can be used wisely if you’re aware of its limitations.

A constant power output gives the fastest time.

You’ll not be happy about this if you’ve just bought a power meter & you think that if you find your FTP (Functional Threshold Power) and ride at exactly that then you’ll produce the fastest time possible, that’s not what will happen.

Every race will have slightly different gradients, slightly different wind conditions, different weather, traffic etc, there’s plenty of variables. It’s been shown that if there is a small hill with a subsequent small descent, then it’s best to power over that slightly and recover on the downhill (you’ll always find it much harder to maintain high wattage downhill, so it’s almost an enforced rest). It’s also been shown that the differences in power outputs when riding in a tailwind are much smaller relative to the difference in speed you gain, so shoving out a load of watts in a tailwind won’t necessarily gain you that much time. The opposite is true in a headwind, where large time gains can be gained through smaller changes in wattage.

So for those using power meters there are some very specific strategies you could use to achieve the fastest time possible by varying your wattage throughout your ride depending on gradient & wind conditions. An absolutely constant power output is never likely to give you the best result, it’s worth experimenting to see what works best for you.

Aerodynamics is irrelevant when climbing.

Take the Tour of the Campsies time trial as an example, the fastest riders can be seen climbing ‘The Crow’ on the tri-bars, Arthur Doyle is a prime example of this, look over some recent photo’s if you don’t believe me. If you require heavier aero kit for the rest of the ride, you may as well use it on the inclines. We can also see that pro riders like Richie Porte used tri-bars during Paris-Nice to win the Col d’Eze time trial. Porte opted for this setup over the lightest possible bike he could use, he did this because it proved faster, I trust Sky’s boffins to be able to calculate this kind of thing correctly.

Again, there’s more to this than meets the eye, pro riders are climbing significantly quicker than amateur riders, so there will be a larger effect the faster the climbing speed. Any rider will gain an advantage from using tri-bars & aero kit on anything but a straight out hill climb.

Conclusion

Hopefully I’ve given some riders something to think about, I really hope I don’t see those kinds of photos from early season again, with riders who look like they’ve not even spent 20 minutes setting up their TT bikes correctly. Put you bike on a turbo trainer, set up a mirror so you can see your position and aim to get ‘in the tube’, i.e. everything apart from your legs into an imaginary horizontal tube. The smaller the imaginary tube you can fit your body head & arms into, will generally prove to be the most aerodynamic, but remember not to go too extreme or you’ll reduce your power output too much. It will take some time to perfect, but it’s worth much more time to you than buying the next very expensive bit of aerodynamic kit and not using it optimally, or even worse, it slowing you down through poor setup.