Myths Debunked: Bigger Wheels DON’T Roll Faster

Myths Debunked: Bigger Wheels DON’T Roll Faster

As part of our series on myths in cycling, let’s look at wheel size and how it affects speed. Even though all-road tires have grown wider in recent years, many bike makers have stuck with 700C wheels. It’s a size that is familiar to road cyclists, and there is also a fear that smaller wheels won’t roll as fast.

When we developed our Rene Herse tires, we tested all aspects of how tires perform – especially on rough roads. As part of that testing, we examined the performance of the common wheel sizes – 26″, 650B and 700C – on smooth and rough surfaces. We found that all wheel sizes roll at the same speed on road surfaces. This contrasts with mountain bikes, where a similar study has found small, but significant, speed benefits for larger wheels.

At first sight, it seems to make sense that a larger wheel might roll better over obstacles and road irregularities: With a larger wheel, the bump becomes comparatively smaller, effectively smoothing out the road. And we all know that a wheel rolls faster on a smoother road…
However, the difference between common wheel sizes is relatively small: Only about 10% between a 700C and a 26″ wheel (above). The approach angle – the angle at which the wheel is hitting an obstacle – is almost the same for both wheel sizes. Even when hitting a rock that is 4″ (100 mm) tall at its corners, the difference in approach angle is less than 2°. For smaller obstacles, the difference is even smaller.

We tested three common wheel sizes in our famous ‘rumble strip’ testing. On a bike, rumble strips feel like the roughest cobblestones in Europe, or like very rough gravel. The goal of our study was to simulate the cobbles of Paris-Roubaix or the roughest parts of a gravel event like Unbound Gravel at race speeds.

We chose the rumble strips of a brand-new highway as our test course, because they provide a uniform ‘rough surface,’ allowing us to test different setups in a carefully controlled setting. The smooth asphalt next to the rumble strip provides a comparison to judge how much energy is lost due to the vibrations of bike and rider.

We tested on a day with no wind and with constant temperatures. (Warmer temperatures make tires softer, which reduces their rolling resistance.) We did three test runs with each setup. The wheel sizes were tested in random order.

We tested otherwise identical 38 mm-wide tires (Schwalbe Marathon HS) in three wheel sizes: 700C, 650B and 26″. We measured the power required to pedal the bike at 32.2 km/h (20 mph) using an SRM crank.

The columns above show the averages for the three runs with each tire size. Every scientific study must perform a statistical analysis to ensure that the conclusions are based on real differences, and not just ‘noise’ in the data. (All measurements have some variability from one measurement to the next.) The dark part of each column is the ‘confidence interval.’

Looking at the first three columns, there are very small differences between wheel sizes. They fall within the dark bars – they are not statistically significant. This means they are too small to tell whether they were real performance differences or caused by ‘noise’ – variability between test runs. (And in real life, they are also too small to matter.)

The fourth column shows what happens when you reduce the air pressure slightly. We did that to check whether small variations in tire pressure might affect the results – it’s impossible to inflate tires repeatedly to exactly the same pressure. The differences were small – not enough to affect our results. (This is one reason why we tested with stiff tires. With supple tires, lower pressures roll significantly faster on rough terrain.)

We also tested each setup on the smooth pavement next to the rumble strips. We found – not surprisingly – that larger wheels also don’t roll faster on smooth roads. More importantly, this test allowed us to confirm that our tires were identical in their construction, and only differed in their wheel size. We wanted to make sure that the tires in the three wheel sizes were not slightly different in some way that made them roll slower or faster. There was a little variability – the inevitable ‘noise’ – but the differences were not statistically significant. On the smooth pavement, the three wheel sizes required the same power, too.

The conclusion: On ‘road’ surfaces ranging from very smooth to very rough, the three common wheel sizes (700C, 650B, 26″) offer the same performance. For road or gravel riding, a 10% difference in wheel size is too small to affect the bike’s speed in meaningful ways.

What about mountain bikes? Many riders report that 29ers with large 622 mm wheels roll much faster over really rough courses than traditional 26″ mountain bikes with 559 mm wheels. Even Nino Schurter (above), long a protagonist of the ‘in-between’ 650B wheels, now races on 29ers – and continues to dominate the sport.

In 2015, researchers at the Swiss Federal Institute of Sport performed an experiment similar to ours, using mountain bikes and a real off-road course. They wanted to find out whether the Swiss national team should ride 29ers or 26″ mountain bikes at the 2016 Olympic Games. The study’s use of real-world conditions is a plus, but it also introduces much more noise. The study used ten riders from the Swiss national team, each doing three test runs over the same course on their 29er and their 26″ mountain bike. Using many riders helps reduce the noise, which averages out the more data you collect.

The Swiss researchers measured heart rate, power output, and speed. Standard scientific procedures were followed: They made sure temperature was constant, they calibrated their PowerTap hubs (there are significant variations from one hub to the next), etc. All ten athletes were faster on the 29ers, on average by 2.4%. The statistical analysis showed that there was more noise in the data than in our rumble strip experiment, but the results were statistically significant.

What the test couldn’t show is why the 29ers were faster, since it did not isolate any of the factors. The bikes were top-of-the-line mountain bikes from the riders’ sponsors, and the 29ers may have differed from the 26″ bikes in other ways, not just in the wheel size. Back in 2015, 29ers were brand-new on the market, whereas the 26″ bikes may have been older models. The purpose of the Swiss study was to determine which bikes the riders should use for the Olympic Games, and the result was clear: Among 2015 mountain bikes, the 29ers were faster – for all riders, no matter their height and weight.

If the study had included 650B bikes as well, the results would have been more informative. If performance had improved across three wheel sizes, then the conclusion that larger wheels roll faster would be easier to make. Including more wheel sizes might also address whether mountain bike speed goes up linearly with wheel size. If that is the case, why stop at 29″? Even larger wheels should improve the performance of mountain bikes further.

Summarizing the two studies, the rumble strip tests showed that on smooth and rough roads, larger wheels don’t roll significantly faster. The Swiss study suggests that, for mountain bikes, larger wheels may be what makes 29ers faster than smaller-wheeled mountain bikes. It’s one more example where mountain and (all-)road bikes really are different.

Back to road bikes: If larger wheels do not offer better performance – whether on road, gravel or cobbles – then we should select the wheels size of our bikes based on other considerations. Leaving aside issues of fit – smaller wheels make wide tires easier to fit on a bike, especially on smaller frames – it comes down to the handling we want from our bikes.

The best road bikes offer nimble handling that makes them easy to place on the road. Wider tires introduce more stability through a variety of factors (pneumatic trail; gyroscopic forces). The result: The bike becomes more stable – too stable for many riders’ tastes.

To keep the nimble handling of a racing bike, you need to keep the rotational inertia of the wheels the same – by reducing the rim diameter to make up for the taller (and heavier) tire. That is why 650B wheels are popular for all-road bikes. With ultra-wide tires, 26″ wheels make sense, too.

Rotational inertia affects not only the handling, but also how the bike feels when you rise out of the saddle and rock the bike from side to side: If your wheels have too much inertia, the bike becomes harder to rock – and that may actually slow you down.

Conversely, racing bikes have stuck with large 700C wheels even though smaller wheels would be lighter and – in theory – ‘spin up’ faster. I suspect that you need some inertia to push against when you rise out of the saddle. You probably want just the right amount of rotational inertia from your wheels for sprinting.

What does this mean in the real world of high-performance all-road bikes? We’ve already shown in the first part of this series that wider tires don’t roll slower than narrow ones. So there is no need to get a second, ‘go-fast’ wheelset with narrow tires for your all-road bike.

However, you do want to go to smaller wheels if you want to keep the nimble handling that makes a road bike so enjoyable. And avoid heavy tires: Wide tires have more rubber, and the effects of a lightweight tire are much more pronounced than they are on a narrow tires for racing bikes.
In practical terms, here are the wheel sizes that I like best:

  • 700C x 28 mm
  • 650B x 42 mm (with aluminum rims)
  • 650B x 48 mm (with carbon rims)
  • 26″ x 55 mm (with aluminum rims)

When you calculate the rotational inertia for all these wheels, you’ll find that they come out the same. That is why bikes with these wheels feel very similar.

How you want your bike to handle also depends on personal preference and on your terrain. If a road bike doesn’t feel stable enough for you, choose a larger wheel to gain stability. If you want even more nimble handling, you can go down a wheel size (or use narrower tires).

Update 11/17/2020: We’ve just published our new book ‘The All-Road Bike Revolution’ with all the research that has changed cycling in recent years. Find out why wide tires can be fast, how to find a frame that optimizes your power output, and how to get a bike that handles like an extension of your body. More information is here.

Share this post

Comments (18)

  • Harald

    To save readers the searching, here’s the Swiss study:
    Always nice to read well-done research.

    April 29, 2019 at 4:30 am
    • Jan Heine

      The study is also linked in the ‘More Information’ column at the bottom of the post.

      April 29, 2019 at 8:02 am
      • Harald

        Apologies, I hadn’t noticed that. And, even better, your link actually provides a non-paywalled version of the paper.

        April 29, 2019 at 8:56 am
  • Simone Baffelli

    A small detail: Nino Shurter should be spelled “Nino Schurter”, in the German way (I’m sure Jan knows better than me ;).
    Although the (non-racing)cycling world gained a lot from your entering the industry, I feel your honesty and integrity are sorely missing in academic research, where one seldom sees such open admission of mistakes.

    April 29, 2019 at 6:11 am
    • Jan Heine

      As cyclists, our goal is to advance our understanding how bikes work to improve our cycling experience, not to be right or wrong.
      Thank you for the correction of Nino Schurter’s name. It’s fixed in the post.

      April 29, 2019 at 7:33 am
  • Grant

    In the early 2000s I worked in the industry and hardly ever touched my road bike. I was all about mountain biking in those days. When the first 29ers were debuting, even with rim brakes and 3 inches of travel it was apparent then that they were better over the bumps. It’s subtle, but noticeable. I think the key to understanding why is to realize that the tire strikes *earlier* since it sticks out further in front of the bike. This means the vertical impulse happens slower since there is more time spent traversing up and over the bump. All that said, it’s a trade-off, and I personally do not think the trade-off is worth it for all-road riding (and non-technical trail riding, as well). Larger wheels are significantly heavier and also more delicate for a given hub width due to the spoke angle. Also, with drop bars all that tire clearance can do weird things to the frame geometry since bikes with flat bars have a much longer top tube for a given reach.

    April 29, 2019 at 6:16 am
    • Grant

      I think the real key to understanding this is in Jan’s philosophy about suspension losses… The ones that occur in the rider’s body. The rumble strip test uses bumps that are small enough that a lot of the impulse will be absorbed by the tire. Once you start hitting bigger bumps, your tissues are going to start bottoming out against themselves more.

      April 29, 2019 at 6:23 am
      • Jan Heine

        Suspension losses don’t just occur on big bumps. They mostly occur when the bike vibrates, even on smooth roads. The rumble strips caused intense vibrations that the tires could not absorb. That is why the power output at the same speed was 70 Watts higher on the rumble strips, even with 38 mm tires. Most of that energy was absorbed in the rider’s body. (The tires didn’t get hot!)
        After riding 25 kilometers (15 miles) on the rumble strips during the course of a single morning to test various setups, my whole body tingled. Even muscles that I don’t use for cycling were sore.

        April 29, 2019 at 7:47 am
      • Grant

        maybe this will be the next big workout craze, vibrating your whole body to get at all the little muscles normal gym equipment can’t touch

        April 30, 2019 at 7:02 am
  • Jan Koegel

    If you have a closer look related to MTB you will find different reasons.
    For example, you mentioned CC races. To win a WC race it is important to be able to set apart especially in the downhills from your chaser before the finish line. One step is to slackened the head angle from 71 to 69,5 to get a more stable, confident and faster bike. With the bigger wheels you will have a better center of gravity related to the wheel axle with similar results. Bottom line, you can go a little bit faster through rough terrain.

    April 29, 2019 at 7:43 am
    • Conrad

      This is kind of what I was thinking. Mountain biking today is not like it was 20 years ago. The winning moves in mountain bike races are usually on the downhills on a course built for bikes. Bombing down purpose built mountain bike trails, I think that the new wheel size and geometry really are dialed for that style of riding. For the more traditional style of mountain biking: say you are going a long distance on a trail not purpose built for bikes and spending as much time going uphill as downhill, and say you rode to the trailhead instead of driving there….I think 26 inch wheels are still the best for this application. To put it another way, if I wanted the best possible bike for an XC or downhill mountain bike race, I would absolutely go with a modern mountain bike. For the high cascades 100, I’m bringing my old Bontrager hard tail and I dont think I will be at a disadvantage on it. Sure wish I had some knobby Rene Herse tires for it though 🙂

      April 30, 2019 at 9:29 am
  • Mark Hillman

    Thank you again for honest scientific information. Having owned and toured on a Bike Friday NWT with its small wheels, it was only a short time before i realized the comfort and safety issues related to the rolling and center of gravity problems associated with small wheels, particularly for “rough stuff” touring.

    April 29, 2019 at 8:13 am
  • mtbvfr

    Hi Jan,
    If the Rat Trap Pass has the optimal width for a 26″ wheel, under what circumstances would you recommend using the other Rene Herse tyres in the 26″ range?
    Thanks, MTB.

    April 29, 2019 at 5:36 pm
    • Jan Heine

      The narrower 26″ tires are great options if you have a 26″ bike that doesn’t fit the really big tires, or you prefer the ride of a narrower tires. They also are great for bikes with smaller frames, where larger wheels cause fit and toe overlap issues.

      April 29, 2019 at 7:07 pm
  • Tommy p

    Jan, it might be nice to note that more professional downhill racers are riding 29″ bikes these days. It’s becoming less common to see 26″ and 27.5″ DH race bikes in the world cup series. Their entire goal is to get down a mountain as fast as possible, so these bigger wheels definitely roll faster in this environment.

    April 30, 2019 at 6:47 am
  • mackenzy

    I’ve been looking for a 26″ x2.1-2.3 XC tire with hard pack tread to put on my Mavic 717 wheel set for my all road camping bike. It’s disappointing to see how fast the industry dropped most of the high quality/lightweight tires of this sort in 26″. I’ve even had a few bike shops laugh when I phone them to check on their 26″ stock.
    I’m really hoping that something like that RTP with knobs comes out soooooon. 🙂

    April 30, 2019 at 11:03 am
  • Charlie

    Jan, thank you so much for your blogs. I just found them and I’ve been really interested in your thoughts. I guess this question is a bit off topic, but it’s been bugging me for a while now. If wider tires have so many advantages over narrow tires, why are so many road racers riding on 700c rims and 25mm tires? Is it the nimbleness? Surely it can’t be about the speed.
    Thanks again!

    May 1, 2019 at 10:51 pm
    • Jan Heine

      Our testing has shown that on smooth roads, 25 mm tires are as fast as wider ones. So for a smooth-road race, 25 mm is a logical choice: You get the lightest tire that rolls fast. A wider tire would get you more cornering grip, but races aren’t won by outcornering the other racers, but by outclimbing them. And when a 5-second difference on a 10-mile climb can make the difference between staying with a group or getting dropped, weight actually can matter.
      Wider tires do offer greater speed and puncture resistance on rough roads, and many pros ride 30 mm-wide tires tires on the cobblestones of the Spring Classics. The science suggests that wider tires would be even faster, but the pros are limited by what the bikes of their sponsors can run – and by the age-old belief that wide tires are slower. Witness one favorite in this year’s Paris-Roubaix running 25 mm tires, hoping that mounting them tubeless would give him the necessary puncture resistance. After multiple flats, he switched to a spare bike with wider tires, but it was too late…
      For the rest of us, 5 seconds on a 10-mile climb is meaningless, and the roads we enjoy aren’t as smooth as the roads of the Great Tours in Europe. So for us, 25 mm tires limit the enjoyment and the speed of our rides, even if we stay on paved roads. And once we venture on the wonderful gravel roads that offer almost no traffic and a unique cycling experience, we need at least 42 mm tires for comfort and speed.

      May 3, 2019 at 1:13 am

Comments are closed.

Are you on our list?

Every week, we bring you stories of great rides, new products, and fascinating tech. Sign up and enjoy the ride!

* indicates required