Category: Essays

With riders publishing their stats to Strava and Garmin Connect, among other places, it’s becoming easier than ever to understand the gains available to cyclists. And more importantly to this post, it affords us the ability to compare real world aerodynamic performance with the claims made via wind tunnel testing.

According to data released by FastFitness (who compile the publicly available stats) the following image is a breakdown of factors that cause aerodynamic drag and frictional resistance on the bike. Let’s take a look a the top four.

Body mass drag accounts for 18.8% of overall losses and Specialized claims it is 80% of the total drag. Which makes sense. Next up, the handlebars and stem accounts for a whopping 14% of cycling losses. Did you expect that? Finally, third runner up is clothing friction at 8.5% followed closely by frame drag at 8%.

So what is all this talk of drag?

Drag, or resistance, is created when an object “breaks” the wind or has voids that create turbulence. This is why aerodynamic designs are so sleek looking. Recent improvements in cycling technology have largely been about reducing the amount of drag created by the bicycle.

So, the single biggest culprit of bicycle drag isn’t the wheels or the frame. No it’s the handlebars and stem. Any aerodynamic improvements made to ones handlebars and stem setup will therefore have the greatest proportional impact. Which brings us to todays post.

How many watts can you save with an aero Handlebar/stem setup?

In part 1, we looked at the watt savings of loose fitting versus form fitting cycling apparel.

In part 2, we reviewed cycling body positions and the results of real world tests released by BikeRadar and GCN.

Today we’ll take a look at the Handlebar and Stem. And there are two options given to modern road cyclists to improve their aerodynamic performance.

1. Slamming their stem.
2. Aero drop bars

As it’s probably the most considered option, let’s begin with number 1.

To slam or not to slam?

Riders everywhere are slamming their front ends. It’s gone global and it started with the pros switching to more aggressive frame setups. But is it the best option for you (or the pros)?

When comparing rider speed in different body positions at the same watts, BikeRadar uncovered something very interesting. While slamming a stem does make your bike more aerodynamic. It pulls your body down and forward, reducing the exposure of your chest to the wind. However, a more aero position may not be the fastest position.

The reason, is that it makes a rider uncomfortable. You may not notice it over a 5 minute test, but as the ride progresses so does ones fatigues. And there turns out to be perfectly simple explanation for this. We make micro movements to adjust our body when riding in an aggressively aero position. This movement creates drag. The results show it makes a surprisingly lot of it. And as we become increasingly fatigued in a position the number of adjustments we make also increases.

These minor movements are so inefficient that they do more to slow us down than the aero dynamic position would otherwise give. From my own testing, riding a slammed stem for more than a year, I’ve learned that the body does adjust. But there is a point where the reward is less than the effort given. And I have noticed the effect of fatigue that BikeRadar highlighted in their test. So I’ve relaxed my position slightly.

You will need to play around with the position of your stem to find what works best for you. Also, to increase your flexibility (and the position you can ride) try to hold a lower-than-normal position for 10 minutes. Simon, from GCN, was recommended to do this as well by a pro cyclist.

Conclusion: unless you are comfortable riding with a slammed stem, slamming it may actually slow you down. Instead marginally reduce the height of your stem until it’s just still comfortable.

Next up: Should I invest in drop handlebars or should I save my pennies for aero wheels instead?

I don’t know how it is for you, but a lot of the shop talk at my local club rides revolve around aero wheels. “Ron’s pulling strong. It’s gotta be those wheels.”

Is it possible to save more watts with an aero bar setup? Let’s be clear, I’m referring to aero drop bars, not the skinny aero bars used by triathletes or time-trialists.

Interestingly, I’ve never once spoken to anyone about aero drop bars. It just hasn’t come up. But this winter while bike shopping I’ve become increasingly convinced by the data that aero bars may be the key to unlocking the greatest aero improvements we’re seeing. And best of all… aero drop handlebars are available to every cyclist on every bike.

The world’s leading aero bikes such as the S-Works Venge, S-Works Tarmac, Cervelo S5, or Pinerallo Dogma F10 all come with aero drop bars (stock). In fact you can’t order any other kind of bar for the S-Works. They also all claim incredible watt saving statistics. Yet their frames haven’t changed that much in the past 3 years. So where are they getting their extra savings? Maybe it’s the wheels and bars.

In 2014 Bike Rumour published that the Cervelo aero bar saved 4.4watts over the rounded bar. Since then Zipp have released even better bars that report 7.5 watt savings at 40km/hr. Their research showed that a traditional round bar creates 0.74 Newtons of drag, whereas their SL-70 aero bar creates just 0.11 Newtons of drag.

If one were to combine an aero bar with an aero stem, similar to the canyon Aeroad in the picture below, the aerodynamic improvements would likely increase further.

“For reference, a bike [creates] 70–100w [of resistance] at 45kph using the same weighted yaw sweep. And, of course, you, the rider, contribute about 75 percent of the total drag.” [BikeRadar] Therefore, a savings of 7.5 watts is a significant amount. Also, unlike aero wheels where the amount of drag created by the wheel can increase depending on the direction of the wind, aero bars are more uni-directional as they are the first part of the bike to cut directly into the wind and do not create the “sail effect” as wheels do.

Given mild wind conditions, however, wheels will save you more watts. In comparison, Elite Custom did a test comparing Enve aero wheels with standard Mavic “training” wheels. They found that Enve SES 4.5 aero wheels saved 14.4 watts compared with standard Mavic Ksyrium Elite wheels at 40km/hr [Elite Custom].

Conclusion

So should you go for an aerodynamic wheel that could save you 14+ watts or an aerodynamic handlebar/stem combo that could also save you 7+ watts?

The handlebar and stem may be the next aerodynamic frontier. It creates the most drag on the bicycle, so clearly there is a big opportunity to improve it. That said, wheel designs are further ahead than aero drop bars.

A new set of aero wheels start at around $2000 and go up from there. Whereas a new handlebar may only cost a few hundred dollars. If you’re in the market for aero components consider starting with the bar. You may be pleasantly surprised at the outcome.

P.S. Have you done any watt testing of your own? I would love to hear about it and publish it here. Please let me know in the comments.

Welcome to part 2 of how cycling aerodynamics effects the real world. This article will look at body position, training and most importantly how these translate into real results for you.

Introduction – Why I’m posting on this.

Part 1 – Aero gains for clothing

Let’s begin. The Perfect Body Position for Aero Savings

Aerodynamic savings on bicycles can cost a small fortune. What I love about getting gains from body position is that it is 100% free.

It seems pretty intuitive that lowering your body will reduce drag as you are making yourself a smaller object. But, which position is really the most efficient? And does fatigue impact aerodynamics? And when does vascular restriction outweigh the benefits from an aero position?

It turns out these all play important factors, and it’s not as simple as slamming a stem or using the drop bars to get gains. (I’ve tried both of these options).

What does David Miller have to say?

David Millar is a Scottish former professional road racing cyclist. He’s no saint, having admitted to using EPO, but he was the first British rider to have won the leaders jersey in all three Grand Tours. He was also the British Time Trial and Nation champion and has worn of all Tour de France Jerseys.

And, most importantly, he’s the most winningest time trialist that I know of who has shared his training techniques.

A1 coaching did a series of videos with David Miller. And he’s surprising forthright of his experiences with aero testing. He shared that he’s learned, that, “You can acquire as much data as you would like, be it from a home trainer or a wind tunnel, but when it comes down to it, it’s that course on a road where you will be able to gauge [the benefits of position] most consistently.”

He tells a story of working on his aero position with coach Peter Keen who did a lot of research and testing using wind tunnels and science. David thought that he also needed to do a lot of science to get his position right. But Keen said, “You look fast David, pretty much that’s what we’ve learnt. If you look fast, generally you are fast, and you can’t do much more about it.”

BikeRadar’s testing confirmed this line of reasoning. They showed that even though Ben Delaney could ride for a short time in a more aero position, he was actually losing aero performance (from lateral movement and constant adjustments) because his body wasn’t relaxed in that position.

So before we get into which position is most efficient. Here’s what David says are the five things he focused on to improve his position and performance.

Number 1: Get a course, so that tests are repeatable outdoors.

Number 2: Focus on your current position on your current equipment to get a benchmark.

Number 3: Apply training around the course you are trying to improve your time on.

Number 4: Make sure you have all the equipment that suites the course and temperature you are riding in.

Number 5: Race strategy. Your pre-race should be the same for every race.

Using David’s system in the real world

As a result of David’s interview I focused my training around my position. I dropped my stem to a position where I was just comfortable and began adding drop-position sessions into my weekly training.

Here’s what I learned. It’s hard to sustain the same effort in a more compact position. The reason was that my heart rate was higher at the same effort/pace with my body in a more compact aero position. With training I was able to increase high effort segments from 1 minute to 8 minutes on the handle bar drops. 12 minutes short of my 20 minute goal at my desired effort.

Was the training worth it?

Yes … and no.

Yes it was worth it for position training. One year on and I am much more comfortable in that new position. However, the performance gains I did experience from this kind of training did not translate into performance gains for century type rides. My original goal was to improve my functional threshold power FTP as well as my aero position. Instead I improved my anaerobic lactate threshold and my aero position.

As you will see below, it may have made more sense to focus on a less aggressive position.

Both GCN and BikeRadar have posted interesting studies on which body position on the bike is the most aero. However they took different approaches.

GCN did a test where they held the same watts over time and then tested for time savings. Whereas BikeRadar tested various positions and tested for watt savings. I think they are both equally interesting.

GCN’s Body Position Test & Results

GCN tested riding with straight arms on the tops of the bars (non-aero position) versus riding with bent arms with hands on the drops. They saw a significant savings between the two.

Non-Aero Position:

• 200W – 30.2KPH
• 300W – 36.1KPH
• 400W – 39.9KPH

Aero Position

• 200W – 33.4KPH
• 300W – 40.1KPH
• 400W – 43.6KPH

Clearly, riding with your hands on the drops is much faster than riding with your hands on the top bars. But is it the most efficient position? BikeRadar helps answer that question below.

BikeRadar did another test in which they tested 4 positions.

Position 1: Straight arms with hands on the tops.

Baseline

Position 2: Bent arms with hands on the tops.

It lowered his back angle significantly and took his arm angle out of the wind.

Saved an average of 94 Watts which translates to 362 seconds over 40KM at 250 Watt average.

Position 3: Straight arms with hands on drops.

Saved an average of 67 Watts which translates to 214.85 seconds over 40KM at 250 Watt average.

Position 4: Bent arms with hands on the drops.

Saved an average of 112 Watts which translates to 442 seconds over 40KM at 250 Watt average.

However, even though it saved him wattage, he was moving around a lot and it was clear he wasn’t going to be able to stay in that position over 40KMs.

The overall winner?

It turns out that the most efficient position for Ben was Position 2. It saved him slightly less time than position 4, but because it was more sustainable and comfortable, overall his body would be significantly less fatigued holding it over the course of 40 km’s and would give him the greatest gain.

 

Here’s both BikeRadar and GCN’s videos:

BikeRadar – Finding the perfect cycling position

GCN – Aero challenge. How much time can you save?