AASQ #103: Why would you want a wheel size larger than 29″?

It wasn’t so long ago that the idea of 29″ wheels seemed far-fetched at best and completely unnecessary at worst. Now, in 2021, the most frequently raced mountain bike wheel size will be 29″, across XC, Enduro and Downhill disciplines.

Why? Because, just as 27.5″ wheels proved to be faster than 26″ wheels, 29ers are faster for most (not all) riders. For racing, it is a no-brainer.

But, will it top out at 29″? Can advances in bike geometry, suspension linkages, axle standards, rim technology, and tire casings come together to make wheel sizes larger than 29″ a viable alternative? Of course, for small riders, 29″ wheels are already pushing it…

While many get on with it very successfully, some short pro-riders who were asked to race 29″ bikes have pushed for a mullet option as they feel it gives them better control over the bike, especially when it comes to cornering. For very tall riders, however, it could be another story entirely.

What does the future hold for bicycle wheel size options? Will we see 30″, 32″ or 36″ in any considerable volume? We touched base with the industry to find out where things are headed. We asked the experts at brands who are already producing bikes with wheel sizes larger than 29″, and R&D teams at brands who have yet to send anything to production.

Thank you to DirtySixer, Marin Bikes, HUNT Wheels, TrueBike, Vittoria and Cube for sharing with us some insight on the topic.

There is a rumor of a slightly larger wheel for gravel-type experiences, but it’s yet to be seen if the benefits of this wheel standard change can outperform new tubeless tire technology with larger tire volumes and lighter casings. – Marin Bikes

Q&A: Why would you want a wheel size larger than 29″?

Does a wheel size larger than 29” have merit across road, gravel and MTB disciplines?

True Bike: First, we should mention the well-known comparison between wheel sizes and the impact on the quality of the ride. We can see that a bigger diameter brings better traction and a smoother ride over obstacles, an obvious advantage of big wheels. The problem is the static weight, of course, which is huge. It is said that it is associated with reduced acceleration speeds.

However, this is questionable. I would argue the opposite. If we use the same power for pedaling the angular acceleration of the big wheel is smaller. But, because one pedal revolution covers a longer distance for the whole bicycle, the question is which wheel size has the higher final speed in the same amount of time?

It would be interesting to measure the difference between how much power (and how many pedal revolutions) are needed to travel the same distance over the same time with different wheel sizes. My personal riding experience indicates that the 36” wheel wins every time.

Also, the maximum speed a 29er is able to reach with the same gearing is higher. And, last but not least, it is a more comfortable ride. The higher volume of air in the tires makes the ride more comfortable with reduced need for suspension. And, thanks to the higher rotational inertia of the wheels the angular momentum is huge, so the bike keeps tracking a line and can be ridden hands up anytime even at low speeds.

But, back to the question at hand. I think larger wheels have merit in MTB and gravel but the weight needs to be cut dramatically. We tried it with our MTB model with carbon rims (Alchemist/Braus), lightweight tires (Vee Rubber off-road) and an alloy frame. The final solution would be a carbon frame and fork, instead of the suspension one we used (MRP).

I don’t think the larger wheels will be ever used for racing. But, remember what people said when 29er appeared on the scene. Anyway, to use it for a fun, relaxing ride, commuting or for long distance trips as a bike-packing bike, I can only recommend.

And the road bike? I haven’t seen a road bike with larger diameter wheels than 28” yet but that will change. We are working on something.

HUNT: Thanks for the questions, there are definitely pros and cons to any wheel size. In theory, a wheel bigger than 29” carries the same advantages as 29” did over smaller wheels such as better rollover and a bigger contact patch.

However, just like a 29er can create fitment issues in smaller frames, so too would an even bigger wheel. To accommodate a large wheel such as a 36”, you’d need to lengthen the wheelbase considerably, splitting the extra length across both the front- and rear-centers. Otherwise, you’d encounter tire clearance and toe overlap issues.

Structurally, to handle such increases in leverage and maintain ride performance, tubing sizes and junctions would need to be reconsidered, almost certainly leading to heavier frames. Likewise, current proportions within the wheel system (i.e. Hub flange diameter and width, axle OLD, spoke thickness etc.) would need to be revisited to ensure wheel performance remains consistent.

In addition, just as some riders prefer the maneuverability and acceleration of smaller wheels, wheel sizes larger than 29” would exaggerate this difference. However, once up to speed a larger diameter wheel could hold a faster average rolling speed, ideal for Marathon or Ultra races. Equally, the better rollover could be advantageous on more chunky off-road trails.

Proportionally, a wheel bigger than 29” would likely cause issues for average height riders, however for those 190cm and taller it is possible it could create a more balanced bike.

DirtySixer: Short answer: YES.

Long answer: For DirtySixer, the 36″ wheels were never meant for someone 5’5″ to hit the trails, but for anyone over 6’6″ to feel normal on a bike and ride with an unprecedented level of safety. I created DirtySixer from the simple need for a bigger and safer bicycle for myself, as I’m 6’6” with some change.

It all started after I broke my ankle in a crash riding a regular and unstable 700c wheeled frame in 68cm size. I worked for 2 years on the initial R&D of my 36” (787 ISO) wheel bike, with the design help from WaltWorks, James and Todd at BlackSheep and other bike engineers like Bryan Keener and Sherwood Gibson of Ventana.

We were using existing rims and tires but thanks to WaltWorks, Vee Rubber created the first real 2.25” MTB tire. I launched the DirtySixer brand in 2013 hoping to bring the best, proportional solution to tall cyclists with Road, All-Road and MTB models.

Little did I know it would convince Shaquille O’Neal (7’1”), Rudy Gobert (7’1”) along with many other Utah Jazz players like Jonas Jerebko, Joe Ingles, Kyle Korver, Donovan Mitchell, Kevin Durant (6’11”), Lebron James (6’8”), Mark Eaton (7’4”) or Rik Smits (7’3”) and hundreds of other tall cyclists.

Their enthusiasm as early adopters and now ambassadors, has been uplifting. Now a lighter gravel tire is available and even a carbon fiber rim. Tall people have all the advantages of riding the big 36” wheel size, but soon more riders will be able to enjoy this wheel size, as the new line of DirtySixer bikes will come in smaller frame sizes.

This will allow big wheels enthusiasts from 5’9” to ride our size XL on the new All-Road line, that will even come with an electric assist version.

-36” wheels are fun! They bring a huge smile to everyone (riders and onlookers), not only because they are the biggest wheels available, but also because it makes you feel like a kid again. That’s what Mark Eaton (7’4″), among others, said. Advantages over 29er for Road: 5*, Gravel: 5*, MTB: 5*.

-36” wheels have a lower angle of attack, allowing the tire to literally float over rocks, roots, cobblestones or potholes, where a comparable width 29” tire would hit harder. Think of the “Magic Carpet” feeling. Advantage over 29er for Road: 3*, Gravel: 4*, MTB:5*.

-36” wheels allow for larger tire air volumes, when directly compared with 2.25” tires on 29” wheels, adding pneumatic comfort. Advantage over 29er for Road: 3*, Gravel: 4*, MTB :5*.

-36” wheels have a bigger contact patch and therefore allow for more traction. You will get more cornering speed and, when losing traction, it will happen later than on a similar 29” tire. Drifting will also be more predictable and easier to control. Advantage over 29er for Road: 2*, Gravel: 4*, MTB: 5*.

-36” wheels carry more momentum with their higher gyroscopic effect. It means you can stay up to speed with less effort. Some will point out the weight. It is inherently heavier compared to a 29” wheel since there is indeed more material at the rims, tires and inner tube. But in real life, this weight doesn’t penalize you as much as you’d think from a dead start and again it helps you carry momentum when up to speed. If you’re not racing, it’s a no brainer. Advantage over 29er for Road: 3*, Gravel: 4*, MTB:5*.

-36” wheels dictate a longer wheelbase and better weight distribution. For us tall riders it means saying goodbye to the usual 80% of riders’ weight hanging over the rear axle. It means you won’t be wheelie-ing your way up the hill. And, going downhill you will enjoy safe, stable and predictable handling even at high speeds. No more shimmy or front wheel wobble. Advantage over 29er for Road: 4*, Gravel: 5*, MTB: 5*.

-36” wheels mean a slightly higher BB, allowing us to use longer cranks, for us with long legs, without fearing pedal strikes or toe overlap. Advantage over 29er for Road: 5*, Gravel: 4*, MTB: 4*.

-36” makes a very distinctive bike, being both very visible to pedestrians and cars, providing a better view of your surroundings. This is a useful aspect for urban riding, in traffic, as you dominate over most non-SUV cars. Advantage over 29er for Road: 5*, Gravel: 4*, MTB: 3*.

-36” wheels are the best for tall riders over 6’6”, no doubt. A 3XL DirtySixer 36er bike will be a better bike than any custom made 29er/700c, due to all of the for all the advantages that come with 36” wheels. But, also for the DirtySixer tall rider-specific ergonomics and the quality of the oversized fabrication of the frame/fork. Advantage over 29er for Road: 5*, Gravel: 5*, MTB: 5*.

On the topic of other big wheel sizes, DirtySixer was the first to introduce a prototype with 32” wheels bike (686 ISO), when the same rim/tire as the 36″ became available from Unicycle (the 32” wheels were first seen at Walmart on a cheap cruiser).

I welded that first one (in titanium). See it here in its Klunker form on February 2016 at UBI, Ashland, OR. I made another 32er prototype in aluminum as a gravel and all-road version too.

NB: Last note, let’s keep in mind it is still far-fetched to compare today’s 29er and 36er rim and tire technology. The 29er has a little more than 20 years of dedicated R&D from the entire bike industry, across all brands. Now, compare that to what was allocated to 36er development in terms of R&D by basically two tire makers, and you’ll get why we are still working on getting better/lighter rims and tires. Tire molds are a huge investment! 

Marin: While we’d be foolish to say specifically “no” to this question, through our testing on wheels larger than 622/700C, we have not found any major performance increases that outweigh the detractors. The balance between wheel size, rotational mass, and weight are all very important to bike handling and ride quality, as well as playing in with bike fit to the rider size.

Through the trend of increased tire size and volume on all major bike categories, we have essentially grown wheel sizes recently and are experiencing the benefits of larger tires for a lot of reasons. Some of those benefits are purely based on the fact that a higher volume tire gives a larger diameter wheel.

Seemingly small changes in tire volume have been revolutionary in everything from pro road racing to trail mountain biking, but it has also meant changing standards and spending time finding the sweet spots of bike geometry, proportions, and clearances for the bigger “meats”. 

With all of that said, we definitely believe in wheel and tire size being a big part of the ride experience, and if there is a new and/or better experience to be had on a bicycle we are always open to checking it out!

Vittoria: Here are my thoughts on this topic:

As we’ve experienced within all disciplines, a larger wheel can provide benefits when rolling through rough terrain, as well as in grip due to the increased size of the contact patch. For these reasons, 29”/700c has established itself as a balance point, where benefits are greatest, and drawbacks are minimized.

So, in theory, bigger would be better, right? Well, again, it’s about balancing the traits.

When compared to a smaller wheel size (26” or 27.5”), the benefits of 29” come at the slight expense of rotating weight, un-suspended weight, fitment (especially on suspension bikes and smaller frame sizes), and in handling. While I’ll never say never, moving beyond 29” wheels may only offer a small percentage advantage, but create disproportional drawbacks in the negative points mentioned above.

In this industry, evolution is a constant, which is what makes it so fun. However, as with all new products, the merit must stand alone, and be separate from chasing a trend. When (or if) the time comes where Vittoria feels a new wheel size standard is justified, we will evaluate the benefits, and approach it with an open mind.

As we are in constant communication with our OEM partners, we have the advantage of seeing trends before they happen, and building products around the needs of riders. So far, only a very few select brands have gone beyond the 29”/700c size, and none are selling in volume.

A few notable brands have experimented with 32” and 36”, but as mentioned earlier, rotational weight and fitment are high hurdles to overcome. Only time will tell if these challenges can be designed around.

Are any major bike brands and/or wheel manufacturers (granted, you can’t have one without the other) considering the introduction of wheels larger than 29”? If so, what sizes are under development? 30.5”? 36er? 39er?

HUNT: Whilst I cannot speak for other brands, right now we’re not actively looking to introduce another wheel size into this heated area of debate.

Our product and engineering teams always keep an eye out for upcoming changes or for areas where improvements can be made, but at least in the short term our focus is on optimizing current wheel sizes.

Marin: At this time, we know of a couple of small rumblings of bigger wheels. 36” has been seen in funky cruisers and on custom MTBs for a long time, but seems to have a lot of drawbacks that mean the benefits, if any, are going to have a very hard time overcome hurdles.

There is a rumor of a slightly larger wheel for gravel-type experiences, but it’s yet to be seen if the benefits of this wheel standard change can outperform new tubeless tire technology with larger tire volumes and lighter casings.

In general, we’ve seen a lot of “standards” of wheel and tire sizes change in the last 10-15 years, and the feeling from the market tended to be that settling down on all that disruption of tire/wheel/axle dimensions changing so rapidly was a good thing.

A little bit of disruption is always fun and interesting, but it’s our belief that changing the cross-compatibility of components and gear should not be taken lightly, and should be done for true performance and/or experience gains. Let’s see what the 2020s bring!

Cube: We do not plan anything regarding 29‘‘. Just as an example:

• The front would inevitably come higher and the stack value would increase, which is not desired

• At the rear, there would definitely be space problems with a lot of travel and frames for small riders
• You would have to raise the bottom bracket, which also increases the protrusion height and makes the wheel unrideable for small people

Thank you very much to David Folch of Dirty Sixer, Sam Meegan of Hunt, Robert Dilik of TrueBike, Aaron Abrams of Marin Bikes, Ken Avery of Vittoria and Marie Korzen from Cube for contributing to this week’s Ask A Stupid Question.

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