How much free speed does an aero bike give? The definitive guide!

Still hammering around on your round-tubed road bike with shallow rims? Thinking of splashing some cash and wondering if a fast bike will make you faster? Will it even make ANY difference at all? Well read on my friends, because here is my 100% definitive* guide to aero road bike gains!

For your reading pleasure, I put two of my bikes through their paces around a local test/training loop. To keep it as consistent as possible I rode on two consecutive days, around the same time of day, where the weather was almost identical. Sunny, 15 degrees C and a noticeably annoying headwind on the outward leg. I wore the same kit both days (I washed it in between I promise) and there was no drafting involved.

My local tester is the “Dodges Bakery Loop” a 7.75km / 4.8 mile undulating loop starting and finishing from the bakery. There are only two intersections and you very rarely need to stop. It’s a good mix of rollers, flat, a downhill chicane and one longer “drag” that can really sap your speed. Often I’ll rack up multiple loops over a solid training ride. According to Strava, I’ve ridden this loop over 260 times and am 3rd on the leader board. I know it well.

Test Day 1 For the first outing, I rode my completely un-aero Trek 5200. This bike has lightweight shallow wheels, standard tube shapes and no real aerodynamic parts. It’s still an awesome bike and I can still get into a fast-ish riding position, but it just wasn’t designed with aero in mind. Even so, it’s no slouch and I love it.

Test Day 2 For comparison on day two I took my Canyon Aeroad for a crack! This machine is about as aero as it gets. Okay, so it’s one generation behind the current crop of pro frames, but it feels damn fast. Aero shaped tubes, aero cockpit, deep 62mm carbon wheels, hidden cabling, rim brakes because slowing down is for losers. Sexy AF and puts me in a powerful yet aggressive riding position. This thing was built for SPEED!

I tried to ride the course as consistently as possible, pacing it the same each time (push a little harder on the climbs, ease on the descents). I wasn’t going full gas, but I still put in a decent effort that had me breathing hard. That’s around 3.0w/kg for me. Power was recorded using Assioma Duo two-sided powermeter pedals that I switched between bikes and calibrated before each ride. For “street science” this is as good as it gets. So onto the results!

What can we conclude from the data? Over the loop I averaged 182 watts on the Trek and 186 on the Canyon, a difference of only 4 watts. You’ll notice the max wattage number was higher on the Canyon loop, this is because I had to slow at a junction for a car, then crank it to get back up to speed. It definitely cost me time. That said…

With almost identical power output I was 55 seconds faster on the Canyon Aeroad. I recorded a 1.9 km/hr higher average speed (that’s 1.2 mile an hour quicker). Winner, winner, chicken dinner! The aero bike kills it without a doubt! For the UK club riders out there, that’s about a 2 minute saving on your evening club 10-mile time trial!

But is it all about the bike? Well, no. Not all the speed is down to the bike itself. Part of that increase comes from a more aerodynamic riding position. The Canyon’s drop bars are narrower at 38cm which reduces frontal area and it also has more saddle to bar drop. If I could get lower and narrower on the Trek, that would close the speed gap considerably.

Still, there’s no arguing that the aero bike was faster. Using my back-of-a-napkin quick maths to extrapolate that out to a metric century and you’re shaving about 15 minutes off your ride time. If speed matters to you, get your credit card out and get yourself in the saddle of an aero road bike!

#aeroiseverything

A few final interesting things to note…

  • Rolling resistance; the Canyon has new Conti GP5000 tyres and the Trek rolls on Specialized S-WORKS Turbo tyres. Both super fast rubber.
  • The back straight is the fastest section of the course. On the Canyon I was 4km/hr faster for the same power over the 2km segment (35.9km/hr vs 39.9km/hr). The faster you go, the more aerodynamics matter.
  • The Trek and Canyon are almost identical in weight! There’s a short 6% out of the saddle power climb on the way home which I hit at 301 watts both days. The Trek felt much faster, but both bikes did it within 1 second of each other!
  • YOU are the biggest source of wind resistance on a bike! If your body is *ahem* not a very aero shaped, losing some excess weight can drastically reduce your aerodynamic drag. A good bike fit can also work wonders.

* Totally not definitive, unscientific, non peer reviewed amateur case study.

8 Comments Add yours

  1. 2bikesborg says:

    This is very interesting, and carefully carried out. However, a single trial isn’t enough. A doctor described a similar study that was published in the British Medical Journal about 10 years ago (a Christmas edition, so not entirely a serious article). Here’s the link: 10.1136/bmj.c6801 He bought a new £1000 pound bike (so far below your starting point) and compared it with his old bike, but the principle is the same. Over a year, he flipped a coin and rode one or the other to work, timing each ride. Now, you’ve ridden your course 260+ times, so you could do the same for a month perhaps. Your results are really interesting, and the difference is striking, but you need to run it a few times more!

    Liked by 1 person

    1. Thanks for dropping by! That’s an interesting trial. I could definitely run a long we trial, but one thing I’ve learned is that a change in weather conditions can have a far greater impact on speed than a change in bike. Controlling external factors is the toughest part of an “outdoor study” like this. Having ridden aero and no aero bikes over tens of thousands of km though, I can tell you without a doubt that aero bikes are faster! 😎

      Liked by 2 people

  2. bgddyjim says:

    I agree with your assessment. It’s an assessment I can attest to as well. I also know multiple tests aren’t necessary. #aeroreallyiseverything

    Liked by 1 person

  3. ericritter65 says:

    I have found the same when riding my Trek 1200 triple vs. my new (now three year old) Kestrel. I have found the aero-bike to make me 1-mph faster on most any regular rides. And since I am definitely the least aero bit on either bike, it has to come down the frame, wheels and set-up!
    PS- love the rim brakes, rotors are for sissies!

    Like

  4. The Omil says:

    Just from riding different bikes with different wheels I agree that aero is king. I don’t expect you to devote a sizeable portion of the next year to testing the variables, but I’d guess that a decent chunk of the benefit gained by the Canyon comes from the wheels alone(?).

    Like

  5. Nice read, this makes me miss my Felt AR5. I will soon belong to the Canyon family though. As soon as they get their bikes in stock. haha

    Liked by 1 person

    1. I hear their stocks are pretty low at the moment! Possibly waiting on the all-new 2021 models? I think I bought mine just before Canyon were depleted by increased COVID sales and supply chain issues.

      Like

      1. I am trying to be as patient as I can. haha. I have my eye on the Ultimate CF SL 8.0 Di2. If I can grab this years or next years model I will be happy. Because for now its mountain biking for me.

        Liked by 1 person

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