Is Aero that important?

When cycling is becoming increasingly technical, and we are being bombarded with more and more jargon and marketing, it is hard to know where you still stand. So today I will address the hot topic of aerodynamics and its relevance to the sport.

Although the concept may seem a bit foreign as we usually classify fluids as liquids, but air is a fluid too. Under the laws of fluid dynamics, it must behave a specific way, and this is the faster you go in this fluid, the energy invested to change the velocity goes up exponentially. So this is the reason why you find it harder to open up a sprint and do 65 kph than it is tootling at 30 kph. This exponential relationship between velocity and the force of drag can be explained through the equation: Force of drag = ⅟2  x Density of fluid x Velocity 2 x Drag coefficient x Area. When we actually have a look at this we notice what is slowing us down and what we can do about it. If the '⅟2'  is constant, the density of air cannot be changed (Unless you mount a giant heat gun onto the front of your bike) and we want velocity to be as great as possible, then all we are left with is the drag coefficient and the area. The area is quite simple, it is just how much of your body and bike is exposed to the wind; not much and you'll be keeping up with Bradley Wiggins, lots and you'll be spat out the back door. Think of it like a parachute, hence the trend of paper thin bikes that are so popular currently. Drag coefficient however is not as simple and is a numerical value that takes into account pressure drag and skin friction. So in our 'ideal bike, we want a narrow, smooth (relatively so, refer to "The Dimple Effect") bike with nice tear drop shapes to slice through the wind and reduce the low pressure wake behind you that is keeping you within mortals ability.

I have been saving up this fact because I believe it is the punch line of the aerodynamics argument: between 80 and 90 percent  of the power you are putting is just going to pushing air out of the way. Which confirms that aerodynamics is immensely important in the sport of cycling. And small changes really can have a big difference, because as I said before, there is an exponential relationship between velocity and drag, so the faster you are moving, the bigger effect that little change will make. And considering that you plus your bike wouldn't amount to more than 4000g of drag (I know, sounds small doesn't it?). So removing 20g of aerodynamic drag is going to be more perceptible than taking off your saddle bag, pump and bottle cages to lose half a kg of weight. And if you do perceive a difference, it is probably due to less pressure drag around the rear of your bike after removing your saddle bag. An example of 20g of drag loss is changing from those old shifters by Shimano which had the gear cables routed out of the side and going to more conventional routing through the handlebars. And to all you haters out there aero wheels do make a palpable difference. This is because round spokes generate so much turbulence and switching to a smooth plane surface for the air to flow over is going to make a huge difference.

Unfortunately, this discussion is going to end in a testimonial, sorry. I went from old Trek with standard round tubes and cables flapping in the breeze to a Felt AR, with its beautiful aero shapes, scalloping for the rear wheel to hide in and internally routed cables. Now I do not know if this is because I notice everything on my bike, but the effect of all that was mind blowing, and I'm at the stage now where I would not go back to a bike with none of this clever aero trickery, it really is that noticable. My advice is, if you are in the market for a new bike, go down to your local bike store and have a ride one of their aero frames. Seriously, you'll love it.




Going to overcoming aerodynamic drag.

No one likes a Wheelsucker

By the way, far from a comment on either rider shown in this picture,
because in my opinion they are both legendary.

Wheelsuckers are cruel and heartless riders that lack the confidence to do their own work. Hey look, one just popped into your head didn't they? They are the foul dust that floats in the wake of your bike, in the paraphrased words of F Scott Fitzgerald. If he did cycle. Which I don't think he did. Nonetheless, misquoting aside, we don't like them.

They think they are being smart sitting there as you push air out of the way for them, which sadly is true. They are saving up to a third of their energy which they didn't work for in the first place, while you sweat it out on the front. But in reality, they are only doing themselves a disservice as they are only training at two thirds of the level that you are, and as they unlock themselves from your wheel and pull out from behind you to contest the sprint every one is eyeing up, you know you did all the work to get them to that invisible line that carries much weight in bragging rights. And instead of feeling down and angry, you should be saluting, like Julian Dean (New Zealand rider considered by Thor Hushovd as the greatest lead out man in the peloton) delivering Tyler Farrar over the line in first place. You did all the work through the hard stuff when your heart rate is touching over 200 beats per minute and you are elbow to elbow with a man who has calves the size of ancient Egyptian obelisks.

But really, we all wheel suck. And we are not as bad as I just made you out to be if you are a wheel sucker. Well most of you anyway. It is as irresistible in cycling as EPO to cyclists during the late 90's. I also am a wheelsucker but I hope my cycling friends would testify to the fact that I do my fair share of work too. And really we should be thankful to the occasional wheelsucker, because as they sit there, they are actually putting themselves in the low pressure wake behind us, which in turn lowers your drag coefficient and you end up going faster. That in itself is nicer than pulling some Tom Boonen move where you are left with over 50 km to go and no one to fill your low pressure wake. (In reference to his 2012 Paris-Roubaix attack). And I find it is good motivation you have someone behind you, it gives a marked psychological advantage relative to just rolling alone.

But in conclusion to my extended rant on the common and loathsome wheelsucker, I provide a method of ridding of a serial offender. Patiently wait, and churn out the watts on the front, when an appropriate long climb approaches, thrash it up there in the big 'ring until the delinquent drops off your wheel and suddenly experiences the foreign effects of aerodynamic drag. When they are a suitable distance behind, throw it into the small chain ring and regret all the lactic acid you have forced into your legs. You may then proceed to soft pedal to the top at 8 kph. Trust me, its satisfying.

The Dimple Effect

Zipp's rim dimpling

The tiny detailing that can be seen on a couple of bikes and accessories has so much more science in it than you could possibly imagine, I'm getting excited at the prospect of enlightening you.

Lets start of with why they are there. These dimples are put specifically there to make the surface less aerodynamic. Confused already? Well by making it less aerodynamic, they make it more aerodynamic. I'm making this worse aren't I? Righto, there are two types of drag, pressure drag, and skin friction. Pressure drag accounts for most of the resistance while you are cycling, whereas the skin friction, which is just the friction generated as air passes over the surface, is only a minimal force, so aerodynamicists don't mind sacrificing a little of skin friction to improve the overall performance of the product in the pressure drag sector.

Now to look to a sport that is far less interesting than our own for a few more cues on why the dimples are there. Golf seems like a good place to start. The dimples on golf balls are using a similar principle. And when you have ever tried to explain why they are there, you give a vague description saying that they are there to make the ball fly straight. But it is so much more than that. The dimples are designed to generate a small amount of turbulence which in turn creates a 'boundary layer' which allows the next layer of air to pass smoother around the body, and ultimately stick to the surface for longer. This 'sticking' allows much cleaner airflow and reduces pressure drag considerably and reduces the pressure tail behind the trailing edge. This attribute also makes wheels with this surface treatment to handle better in cross winds because this boundary layer is smoothing the airflow, reducing the pressure drag and from greater yaw angles minimizes the effect of crosswinds on the wheel. All in all, extremely clever.

As well as seeing this in Zipp's line of wheels, Ridley has started employing this on their new road bike the 'FAST' by using a paint job that does this. This utilises stratigically placed strips of 'rough surfaces' that generate this turbulent airflow and creates a boundary layer which makes the air stick to the airfoil for longer and makes the air rejoin clearly which is a huge cause of turbulent airflow and hence pressure drag. These strips are placed where the air starts to detach from the frame, making it the ideal  airflow over the foil.
Also we are starting to see skinsuits with a certain dimpling on their surface. And considering that the body on a bike is two thirds of the drag produced, this dimpling is set to make a huge difference as it is making a difference where it counts.

So now you see the monumental effect of the humble dimple.

The Allure of Tubulars: The end of an era?

The first tubular I mounted was a Vittoria onto an old Wolber rim. There is something immensely special about this process that borders on sacred. We all remember the first time we glued a single but the same nostalgia is not held for its more humble clincher cousin. It is the simple beauty of anxiously waiting while your tyre is sitting inflated dry on a rim before you can even think about applying the first layer of glue.

There used to be a 'Tubular Voodoo' subculture where you would hear of people buying tyres months in advance and stashing them in some unsuspecting nook and crannies under the pretence of allowing them to 'cure'. Now I do not doubt for a second that such a subculture still exists but cycling has moved on from an age of superstitions and has been replaced with cool, hard Science. People trying to extract that extra tenth of a second per kilometer to gain an edge on the competition has flooded the market. In recent times the clincher tyre has been trying to stage a revolution, with arguably more practicality, and new sophisticated supercomputer analysis, it is poised to saturate the traditionally tubular orientated world of professional racing. Manufacturers are now claiming that their new generation of clinchers are actually faster than the sew-ups we so love. Boasting a more aerodynamic profile and lower rolling resistance, it seems the tubular might have finally met its match.

A certain German individual time trial specialist who shall remain nameless due to the unforgivable sin of taking the rainbow stripes in the Individual time trial off the legendary Fabian Cancellara, began using clinchers in his TT stages and has since claimed several high profile wins against the clock. As the technology invested into the research making the clincher a tyre one that can outperform a tubular has increased, it has become the nameless German's tyre of choice for bouts in his favoured discipline. Yet, with flats in both the prologue and the first TT in the 2012 Tour De France, it reminds us that they are still in early development and it seems like it will be a long while before we see the reign of tubulars to be surpassed and become the tyre of choice in the pro peleton.

So do these recent revelations signal the end of an era? I think not, there will always be that nostalgia held in cyclists hearts for the tubular tyre and for the childlike excitement we get when we mount a tyre on a rim that no science can take away. When we are all looking for incremental enhancements, we fail to see the bigger picture, we seem to forget that this is a sport steeped in history and in our quest for ultimate glory, we need to remember the likes of Eddy Merckx who contested most of his races on a set of box style aluminium rims mated to a set of singles. This wheel-tyre combination may well have been 4 seconds per kilometer slower than another set out there that his closest rivals may have posessed. But he still annihilated the competition regardless. Races are won by sheer class. But for me, I know the set of tubulars I keep in my wardrobe when they are not in use to protect them against the harsh ultraviolet radiation, will be my wheel of choice, because that's what they do, exude pure class that cannot possibly be matched by clinchers.