View from the Saddle: Aero

View from the Saddle

is a semi-regular feature where we discuss industry trends, technological innovations, or other industry developments.

Aerodynamics isn't a new trend, but it does seem to be a growing buzz word in marketing circles, thus a prominent feature in the collective consciousness. It seems as though almost every performance cycling product announced these days has some mention of the products aero benefits. While some of these claims are sensationalized, there is no denying the benefits of aerodynamics. However, clever marketing and statistics can make some aero benefits seem to be much more significant than they actually are.

In this edition of View from the Saddle we take a look at aerodynamics and what it means for your average cyclist.

I feel that I should mention a bit of perspective on this article. We are not hard-core racers. The most important thing for us is getting out for a ride. So while it may seem like we scoff at a gain of a couple watts, we fully understand that the difference between a win and a loss can easily be those watts. The point of this article is to simply highlight the various strategies designed to reduce drag and increase speed. It is up to the reader to decide which ones apply to their riding goals.

Wind on the rider

The accepted (and scientifically supported) wisdom in cycling is that overcoming wind resistance accounts for 90% of the energy used in cycling (the other 10% is lost to various forms of friction). So it is clear that aerodynamics are extremely important when it comes to going fast. Additionally, the faster you go, the more important it becomes (more on that later).

Running mathematical models show that in almost all instances aero beats weight. (some examples

here

and

here

). So while it is fun to impress your friends in the parking lot by having them lift your light weight bike, the science tell us that if we want to be faster, we are better off being more aero.

If aerodynamic is so important, how can we call over-hyped?

It is not aero itself that is being over-hyped, but the best places to make aero gains. Companies highlight the aero features that come from products that they cans sell you, while failing to mention that the greatest gains are free (or at most a few hundred dollars). If you are to listen only to press releases, you would think that the new frame/wheels/helmets from Brand-X are what you need to take your riding to the next level. These campaigns can be remarkably persuasive and it is easy to get caught up in the wave.

Before you do, there are some important numbers to consider. As we mentioned above, 90% of your energy goes to overcoming wind (drag). However, approximately 80% of the total drag comes from the rider themselves, the remaining 20% comes from the bike, wheels, and components. This leads to disproportional effect size.

If a new bike is 20% more aerodynamic (which is a significant gain) than your old one, all things being constant, you have an actual effect of only 4% improvement to your overall drag. To achieve an effect of similar size, one would only need a 5% improvement of the wind's effect on the rider themselves (and you don't have to buy a new bike!)

What this example shows is that the largest gains are going to be made optimizing your position. Time and time again, in order to optimize your cycling experience, you need a good fit! In terms of being more aerodynamic, that means getting low and long, minimizing frontal area. If you sit upright, your body is a big, flat sail. If you are low, you body is still a sail, but a much smaller and sleeker one.

Research suggests that an excellent position can reduce drag by as much as 25%. An excellent position would consist of a flat back, narrow shoulders, and knees in close to the bike. Cervelo's research also found that, on average, lowering handlebars reduced drag.

If lower is better, obviously flexibility plays a major role in how low you can get comfortably, and going too low without the requisite flexibility can sap power that would wipe out any aero advantage. However, you would be surprised at the extent of gains you can with just 15 minutes a day of dedicated stretching.

The biggest takeaway from this is: before you go out an buy a new aero bike, take a good look at your position and see if there is an edge to be made there. Both your body and your bank account will thank you.

Aero Bikes

Say you are in the market for a new bike anyway, should you consider an 'aero' model? Absolutely, but know that there are a few other things to take into account with aero bikes.  The two most important of those are ride quality and serviceability.

The traditional aerofoil shapes make for a much less compliant ride. Often these bikes are designed for all out speed, with little consideration for comfort. A perfect example of this would be the Giant Propel. When we tested this bike, we found it to have one of the stiffest bottom brackets we have ridden, on par with some of the top super bikes out there, but it also had one of the stiffest rides of any modern bike that we have ridden. It was quite harsh actually, reminding me of my old aluminum Cervelo S1. There is no denying that the bike was very fast, but we felt that the trade-off was too high to ride it daily.

There are many bikes that are nearly as quick with significantly smoother rides, that make for a much better riding experience. As always, it is always best to ride a bike and see how it feels to you on your roads. One has to simple look at the pro peloton, where the stakes are the highest, to see the importance of ride quality. In this year's Giro d'Italia, many riders of the Garmin-Sharp team made an interesting change in bike selection. Rather than ride the company's top aero bike, the S5, riders are choosing the less aero but more compliant S3. Comfort over pure speed at racing's pinnacle, the horror! I can't imagine that this sits too well with the Cervelo brass, but if it gets them to the podium, they can't complain too much.

On the serviceability front, many manufactuers has starting to include integrated brakes in their forks and framesets. Some of the integrated brakes that we have tried have had quite good performance, some not so good, but none are really on par with a good set of calipers. Performance aside, servicing these brakes are more involved than caliper brakes as well. For example, some bikes (like our recently reviewed BMC TMR01) require the crank to be removed in order adjust the rear brake. Not exactly user friendly, especially if your training wheels and race wheels are different widths.

So those are the downsides, what are the benefits? Looking at various manufacturer data, there are definite gains being made when it comes to bike aero. Scott has the Foil being ~26% better than a 'round-tube bike'. Velo lists a 18 to 23% gain. Trek says its new Madone is 30% more aero than the last generation. These numbers equate to a difference of about 15 to 20 watts, or about 1:30 in a 40km TT. Significant no doubt, but the dollar for watt investment can be pretty steep.

Wheels

Even aero wheels, a popular upgrade, has relatively small gains. According to Easton, their new EC90 Aero 55 wheelset is the fastest in their class on the market (aren't they all, grin), and being the fastest will save you about 1 minute over a 40km time trial vs a standard 32 spoke wheel.

Other data sources give a range of 10 to 25 watt advantage, depending on testing protocol, baseline wheel used, etc. Again, very significant results, but with most wheelsets going north of $2k, not a cheap proposition.

There are other issues that come with aero wheels, such as stability in crosswinds (though modern wheels have come a long way in mitigating that to a none issue), added weight, or reduced ride quality. This article is focused on aero primarily, so those topics will have to wait  for another time.

Helmets

One of the cheapest ways to gain a few watts has long been the aero helmet. While the term 'free speed' is not exactly accurate, the cost of a few hundred dollars is quite minimal compared to some of the other interventions mentioned above.

Numerous sources have the advantage of these helmets at around 8 to 15 watts. The criticism of aero helmets is two-fold: heat dissipation, and looking like a fool. Luckily, they are getting better at both of those.

The biggest change comes from the introduction of the aero-road category of helmets. These have a much more blunted shape compared to their long-tailed siblings, making them a little easier to blend in with the rest of the road helmets, and in some instances safer. Cyclists are generally a conservative bunch, so looking 'different' is usually bad, but their adoption on the pro tour will ease their overall acceptance.

While these helmets do not offer the full benefit of a 'pure TT' helmet, they still provide a significant advantage while coming close to the same heat dissipation as their 'standard' siblings. A nice compromise, no doubt.

Marketing and Data

Cervelo offers many interesting articles on their site pertaining to both their bikes and the industry as a whole. Obviously, any information that comes form a manufacturer needs to be read with a critical eye. While we do not dispute the math or engineering that goes into their articles, we do think it is important to consider what they mean to you and your riding.

For example, in "Just One Meter" they calculate which of their models is faster in a pro sprint. The results tell you that the S5 beats the R5 by about a meter, so it is the better choice. Okay, but what does that mean for the rest of us. Looking at the figures, their test race begins while the riders are traveling 65km/h, averaging 1200watts, with a peak of 2000 watts. I don't know about you, but I don't often find myself in that type of situation. So while the S5 is technically faster based on this example, it doesn't necessarily mean that it is better for you.

In Cervelo's defense, they don't make any other claims other than those stated in their initial parameters, and we find their article to be generally well written and informative. When it comes to choosing a bike, even within the same company, much of it comes down to personal preference. For example, having ridden both the S5 and R5, and knowing that the S5 should be faster in most situations, I still prefer the ride of the R5. Also, with the new kamtail-like Squoval 3 tube shapes  (similar to those found on bikes like the Madone and Foil) add some aero benefit. Furthermore, having ridden both the R5 and R3, I feel that they are so similar that I would save some money and get the R3 (grin).

It is important to try to be honest with yourself as to the type of riding that you do (or intend to do) and what you want out of your bike. Our advice, ride them and pick the one that feels better. As anyone who has read our reviews knows, we value handling, braking, and comfort, over pure speed, so what 'feels' good to us may not be what you are looking for.

Conclusion

To sum up, there is much hype about all of the aero features that are coming to the market, and while the gains are real, their magnitude is small. Get the bike that is comfortable and fits you best, and if that bike happens to be aero, then consider it a bonus. If you are in need of a new part (not just replacing a perfectly-good-but-not-aero part), have the money to spend, or looking to get every last edge, then go ahead and pick up some new aero technology, but do it knowing what to expect for returns.

I think it is important to remember that the number one most important thing you need to go fast is a strong engine. All of the other technology is just to squeeze every last watt out of that engine. I am absolutely certain that you could put Tony Martin on a bike from the 70s and he would still crush 99.9% of the population in a TT.

Remember, fitness is far more important than finances, and don't let the pursuit of more speed get in the way of enjoying your ride.