Lightweight vs. aero road bike wheels: What's best for climbing?

For years, I’ve been telling other riders (and myself) that bike weight doesn’t matter. Sure a bike that you can lift with your pinky finger is pretty cool. And an ultra-light bike definitely has a unique feel when you ride it. But you could give me the lightest bike on the planet, and I’m still not going to beat my grizzled old neighbor riding a porky steel frame up the hill. That’s just the facts.

I even wrote a blog post titled: “Does bike weight really matter?” In it, I made the argument that most cyclists really don’t need to stress about how light their bikes are. For an extremely average rider like myself, a few grams isn’t going to make a difference. Even a full pound of added frame weight probably won't matter. 

But there’s one important caveat: wheels.

If you’re going to shave weight off your bike, the best place to do it is your wheels. Reducing rotating weight makes pedaling, accelerating, and climbing a little bit easier. That’s great for me because climbing is my weakness. Also, pro racers like to swap to ultra-light wheels for big climbing stages in the Tour de France. So obviously, if I want to spend money to climb better, then I should spend it on lighter wheels… Or should I?

Some smart-sounding people commented in my bike weight post and suggested that maybe, just maybe, wheel weight doesn’t matter as much as we think. Depending on how fast you’re going and the terrain, heavier aero wheels might actually be the faster option.

Now, I’ve seen other people test this, but I’m not interested in their results. What I want to find out is whether lightweight or aero wheels will be faster for me, on my bike, riding my local terrain. Fortunately, I just built up a brand new road bike over the winter, a Specialized Allez Sprint, and I need to decide what wheels I want to run. So let’s do some testing to find out if light wheels are actually faster on one of my regular climbs, and if so, by how much.

Lightweight vs. aero wheels

The two wheelsets I’m going to test are the Mavic Ksyrium Carbon Pro SL and the ENVE Foundation 65. The Mavics have 25mm deep carbon rims and weigh 1,445 grams. They are the lightest tubeless Ksyrium wheel in Mavic’s line-up. The ENVEs have 65mm deep rims that provide great aerodynamics and weigh 1,641 grams. The ENVEs are obviously the more aero option, and the difference between the two wheelsets is 196 grams, which is nearly half a pound.

I picked these two wheelsets because they are somewhat close in price — the Mavics are just over $1,700 and the ENVEs are $1,600, both fit my disc road bike, and they were both available at The Pro’s Closet. They’re also both tubeless, which I am a big believer in. To try and keep things consistent, I have both wheelsets set up tubeless with the same, brand new, 25mm IRC Formula Pro tubeless tires. I ran 80psi all around and made sure each wheel had 30ml of sealant. They had the same brake rotors, but I did have to put a slightly heavier cassette (SRAM Red XG-1190 vs. SRAM PG-1170) on the ENVEs, though I doubt that made a significant difference.

The climbing test

The climb I chose is a local one I’m pretty familiar with called Olde Stage. I’m doing the backside of the climb which is fairly representative of the type of climbing I do on a regular basis.

Olde Stage is perfect because it’s straight and only 1.4 miles long. Each climb should take only 9-10 minutes. The grade averages 5.7% but kicks up to 14-15% at the end, so there’s a good mix of gradual and steep pitches. Because the road is so straight, factors like cornering and wind should have very little effect on the final results.

The plan for this test is to do the climb six times, three for each wheel, and then calculate the average time for each wheel. To keep things as consistent as possible, I’ll watch my power meter and attempt to maintain an average power of 250 watts. 250 is an easy repeatable number below my threshold, but still hard enough to replicate what I would do on a normal ride. I’ll also try to keep my body position, cadence, and shifting as similar as possible for each climb.

Obviously, this isn’t hard science, and there’s going to be plenty of details for the nerds to nitpick. Mostly, this is all for fun. And just as important as the times, will be how the wheels actually feel to ride. I’m really interested in how different a light wheel will feel compared to an aero wheel on this climb, especially since I’ll be able to ride them back to back. So let’s get riding and find out!

Results

At the top of the climb.

Mavic Ksyrium Carbon Pro SL

Average time: 9:44.7

ENVE Foundation 65

Average time: 9:53.3

The results might not be that surprising — the lighter wheels were, in fact, faster on this climb. What did surprise me, however, was how much faster they were. The Mavic Ksyrium Carbon Pro SL were nearly 10 seconds faster than the ENVE Foundation 65. On a 10-minute climb, that’s pretty significant.

I think about it this way. Many of my big local climbs are in the 30-45 minute range. If I choose lightweight wheels, I can reach the top, catch my breath for 30 seconds, and then gloat as a version of me who chose aero wheels finally comes into view. An extra 30 seconds could also mean some new Strava PRs that will greatly inflate my sense of self-worth.

Interestingly, without the times in front of me, I never would have guessed that the lightweight wheels were that much faster. I actually thought it’d be closer, within a couple of seconds, and really wanted an empirical excuse to run my aero wheels all the time. Unfortunately that’s not the case.

The ENVEs don’t feel particularly heavy just riding them day-to-day. And when riding them back to back with the Mavics, the extra weight is really only noticeable when starting from a stop and when the road pitches above 7-8%. On those steeper grades, it feels slightly easier to stay on top of a harder gear with lighter wheels. The longer the climb, the more that sort of feeling will be appreciated.

Final thoughts

It's definitely worth swapping to lighter wheels for big climbing days.

I plan to do a lot of high mountain climbing this year. Because the Mavics were definitively faster on my little test climb, they’re the wheels I’ll choose for the majority of my riding. But I’m not getting rid of the ENVEs. Aero wheels definitely have their place, and I’ll use the ENVE’s for flat and rolling road rides where the aerodynamic advantage will benefit me more. Also, they just look better. Deep aero wheels look good on any bike, especially an aero bike like the Allez Sprint. The ENVEs will be the clear choice for Instagram photoshoots.

Overall, I’m happy with how my test went. It was very simple to perform, and it provided very clear results that were easy to interpret. I do wonder how the results would change at higher speeds and power outputs. Perhaps I could do every climb at 275 watts, or 300 watts (though I might lose consistency if I go that hard!).

If I'm moving faster, would the aerodynamics of the deeper wheel have more of an effect? Also, how much time will the aero wheels save if I do a similar test on a flat road segment? I’m going to have to save those questions for a future test. For now, when the road tilts up, lighter wheels are the way to go.