A Tale of Two Rides.
With apologies to Dickens, this morning I’d like to do something I’ve not done in a while: geek out on some cycling data from a couple of very similar rides. This morning’s nerdy indulgence actually has a point, and that is to attempt to gain some insight into the performance advantage provided by aero bars. Secondarily, I’d like to demonstrate that power alone doesn’t tell the story: watts/kg is where it’s at.
In yesterday’s blog, I wrote about the aero bars that I recently added to my main road bike. In that blog I posted some photos, along with my initial thoughts after a couple of rides. While those two rides, which totaled about 75 miles, gave me a good idea of what to expect from my aero bars, I was itching to do a long solo ride that was conducive to a Time Trial effort…
Lucky for me there’s a place fairly close by that is nearly perfect for Time Trial training: The Van Fleet Trail! This trail, ridden out and back (including the 6.6 mile trail extension), is a little over 71 miles (115 kilometers), very flat (only about 250 feet of elevation over the entire 71 miles), straight, remote, closed to vehicles, lightly trafficked by others and there are only a handful of road crossings.
While the Van Fleet Trail is flat as a pancake and straight as a bowling alley, it runs through some extremely beautiful areas. You’ll ride through moody cypress swamps, wide open farm land and more. Wildlife sightings–everything from gators to deer, bald eagles to snakes–are extremely common. Some people hate the trail for what it’s not; I love it for what it is.
Yesterday I rode the entire trail out and back, which is something I’ve done quite a few times before. As I was looking at my past rides at Van Fleet, another ride struck me as very similar to yesterday’s ride. This ride was done just a few months ago, December 18, 2014.
There are two significant differences between the December 18th Van Fleet ride and yesterday’s Van Fleet ride: my weight and the aero bars. On December 18th my weight was around 178 pounds (80.74 kg), while yesterday my weight was 165 pounds (74.84 kg).
First, let’s get a broad overview by looking at the major stats (click to enlarge):
This is pretty interesting data. Let’s dive right in. 🙂
First let’s talk about wattage. My average wattage output was a little higher back on December 18th (221 watts vs 213 watts yesterday). In fact, the 221 watts on December 18th was a new 3 hour wattage personal record, but that was at a higher weight than I am now. My 3 hour watts/kg on December 18th was 2.74 watts/kg, while yesterday my 3 hour watts/kg was 2.85 watts/kg. Just looking at the power numbers doesn’t tell the whole story. Yesterday’s ride was the stronger of the two. Why? Let’s see!
Power alone is fairly meaningless. A 300 pound (136 kg) athlete putting out 400 watts (2.94 watts/kg) for 20 minutes is not nearly as impressive as a 150 pound (68.04 kg) athlete doing the same thing (5.88 watts/kg). In cycling, if two riders put out the exact same amount of power, the lighter cyclist will always be faster. It’s really that simple. Power is important, but power-to-weight is what really matters. This is especially true when there is elevation involved.
Now, let’s take a look at my heart rate. My average heart rate on December 18th was 169 BPM, while yesterday it was 166 BPM. It was actually considerably warmer yesterday than it was on my December ride (75°F vs 57°F average), so the lower heart rate is a little surprising. The temperature on the second half of yesterday’s ride peaked out at about 86°F, and my average heart rate during the second half of yesterday’s ride was 176 BPM. My effort level was fairly constant yesterday, although I did ride the second half a little harder than the first half (217 watts coming back vs 209 watts going out). The increased effort level during the second half of yesterday’s ride certainly affected my heart rate, but the higher heart rate as compared to the first half of the ride was mostly due to cardiac drift, brought on by the heat and fatigue.
My average cadence was nearly the same on both rides: 91 RPM on yesterday’s ride vs 93 RPM on the December 18th ride.
At this point I need to note wind speed and direction. On my December 18th ride I had about a 5 MPH tailwind heading south (outbound), and roughly the same speed headwind coming back. Yesterday I had a 5-7 MPH headwind (increased as the ride went on) heading south (outbound), and a 7 MPH tailwind for about 10 miles heading north, which then (very annoyingly) shifted to a mostly cross-wind for the remainder of the ride.
Okay, with that out of the way, it’s time to look at average speed (note that I was riding solo on both rides). My average speed on December 18th was 21.1 mi/h (33.96 km/h), and yesterday my average speed was 22.1 mi/h (35.57 km/h). I would say wind conditions were actually slightly more favorable on the slower ride (December 18th) compared to yesterday’s ride. So that’s a full mile per hour improvement, under slightly worse wind conditions. While my watts/kg, as discussed above, was higher on yesterday’s ride than it was on my December 18th ride, that is somewhat mitigated by the very flat course.
As an aside, I set 17 new personal records for time on various Strava segments on yesterday’s ride.
All of this brings me to this: the aero bars really help. In particular, I noticed the advantage when riding into a headwind. The entire outbound leg on yesterday’s ride was straight into a headwind; while I definitely was aware of that fact, it felt a little easier than usual. Yesterday’s ride left no doubt in my mind that aero bars provide a speed advantage, especially when riding into a headwind.
Here’s another interesting sidebar to this story. On my December 18th ride I had my Zipp 404 wheels, while on yesterday’s ride I only had the front Zipp (my rear Zipp is at the factory due to a cracked hub flange). Yesterday I was rolling on a cheap 50 dollar rear wheel: heavy, non-aero, and a really crappy hub. I’m sure if I had my rear Zipp on yesterday’s ride I would have been even quicker, perhaps 22.4 mi/h or so.
On a more humorous note (and I’m sure others who ride on aero bars can appreciate this), when I’d move back to the hoods or even the drops for a change of position, I felt like I was absolutely towering over the bike! I felt like a giant–gangly, awkward and definitely not aero! 🙂
If that’s not enough data for your inner-nerd, feel free to check out the rides on Strava: here’s the December 18th ride, Van Fleet + Extension – Solo Sufferfest, and here’s yesterday’s ride, Van Fleet + Extension: Shut Up Legs Edition.