Jans Expert Jeff Walker mountain biking in Deer Valley, UT.

Shifting Trends V: What’s Up With Wheel Sizes?

If you’ve been around bikes much in the last decade, you’ve probably heard a lot of hubbub about wheel and tire sizes changing. For years, the 26” wheel was the only choice for mountain bikers, and the standard 700C hoop was the sole size for road bikes. But bike companies have done a lot of experimenting in the last few years, both in terms of wheel diameter, and rim and tire width.

This has resulted in some confusion and frustration among riders⁠—especially those who purchased a bike only to find the wheel size became obsolete within a season or two. But if you understand the pros and cons of these new wheel sizes, you’ll have an easier time finding out what kind of wheel is right for you. Let’s take a look at some of the recent developments in wheel and tire technology, and find out what makes them worth riding.

29ers

The 29-inch mountain bike wheel was the first major innovation in mountain biking wheel size. In 1999, WTB became the first company to introduce 29” tires to the mountain bike market. People were interested but also skeptical. A common belief was that it was going to be too hard to accelerate or maneuver tight corners. So, riders everywhere set about debunking that myth.

First, 29ers began to profoundly impact cross country racing, even provoking certain racing associations to create a whole new 29er class, thus avoiding an “unfair advantage.” But still, the bike industry thought, surely 29ers won’t work well on dual suspension trail bikes. And then when they did, everyone thought the same of downhill bikes. Now, almost every DH bike on a UCI podium is a 29er.

So what caused 29ers to sweep through the industry? Well, for starters, the larger wheels make it much easier to get over obstacles. Imagine running over a big crack in the sidewalk on a skateboard. Now imagine running over the same crack on a bike. The larger wheels have a much easier time crossing smoothly over the obstacle. Likewise, the bigger wheels carry more momentum through rough sections.

The original fear that 29ers would be hard to accelerate has been pretty firmly debunked, especially with the recent innovations of 1×12 drivetrains and significantly lighter building materials. They may be slightly less nimble, though, as the larger wheels do increase the turning radius. Nevertheless, the modern 29er feels exceedingly maneuverable and capable. If you are a taller rider, or someone who doesn’t often encounter very tight turns, you’ll probably feel right at home on a 29er.

27.5” Wheels

The 27.5” mountain bike wheel is a more recent innovation. These were conceived to be a practical midpoint between the old 26” wheels and the newer 29” wheels. With the maneuverability of a slightly smaller wheel, and the rolling resistance of a slightly larger wheel, the 27.5” wheel seems ideal for those who ride a bit of everything. The smaller turning radius gives these a nimbler feel than a 29”, but the 27.5” wheel still has an easy time getting over roots and through rock gardens.

The slightly lower center of gravity and smaller radius of the 27.5” wheel gives it a more playful, agile feel. For this reason, riders who like to shred bike parks and dirt jumps typically favor 27.5” wheels. If you’re a shorter rider, or you like a bike that is more maneuverable and easier to get off the ground, you’ll enjoy the poppy, nimble characteristics of a 27.5” bike.

Plus Wheels

Plus wheels offer yet another variation on wheel size. Rather than changing the diameter of the wheels, plus sizes provide increased width. Plus wheels are available in both 27.5” and 29” options, and some plus frames are capable of accommodating either size. The width of a plus tire ranges from 2.6 to just under 3 inches. Because the girth of a plus tire is so large, it also increases the circumference of the wheel. This causes a 27.5+ wheel to have a similar circumference to a regular 29” tire.

Plus tires also feature a larger footprint than regular tires. This means that at any given time, a plus tire is making more contact with the ground than a standard tire. By increasing the surface area, the tire has an easier chance of gripping the terrain. Plus tires also have more float, especially on soft, sandy trails. This makes it easier to maintain momentum on loose, washy terrain, like dry lake beds.

However, riders who gravitate towards fast, steep, and aggressive terrain aren’t the best candidates for plus. This is due to the fact that plus tires run at a low psi. The low psi lets plus tires conform to the shape of the terrain adeptly at lower speeds, but they can feel too squishy and unmanageable at high speeds. If your riding often takes you into the desert, where you encounter sandy washes, or if you desire a more supple, stable grip, plus tires may be a great choice for you.

Fat Bikes

Fat bikes take the concept of increasing traction with wider tires, and push it to the max. Perfect for riding on a sandy beach or along a snow-covered trail, fat bikes are like two-wheeled monster trucks. Fat bike tires range from 3.5 to 5 inches in width. Because of their large size, fat bike wheels and tires are at risk of running on the heavy side. For this reason, many fat bike rims have holes drilled in them to save weight. As building materials have gotten lighter throughout the years, fat bikes have seen a swell in popularity.

The latest generation of fat bikes weigh in at around 30 lbs, making them very manageable. They can accelerate and climb without exhausting the rider, and their more streamlined design improves handling as well. If you’re a rider who wants to pedal around in the snow or on the beach, you’ll probably love riding a fat bike.

Mullet Bikes

A mullet bike is the name given to a pioneering new concept which features a 29” front wheel and a 27.5” rear wheel. This Idea was partially inspired by motocross bikes, which commonly have a larger diameter wheel in the front than the back of the bike.

The essential idea behind a mullet bike is to give the rider a large wheel up front, which will bound up and over rocks and roots with ease, and a smaller wheel in the back, which will lower the bottom bracket height, shorten the chainstay, and ultimately make the bike more responsive and nimble. While it may look funny, early reports of the performance of mullet bikes indicate that they may actually work.

While it will probably take some getting used to, the mullet design seems to blend the playful maneuverability of a 27.5” bike with the fast-rolling steadiness of a 29er. If you want to compete in downhilll races or favor the steepest, ruttiest terrain you can find, a mullet might be the bike for you.

By Jeff Walker, Content Writer, jans.com.

Shifting Trends is our latest blog series covering recent changes and developments in the bicycle industry. This is the last in the five-part series. Click here to read our previous post.

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