29 vs. 27.5: What Mountain Bike Is Best For You

by Wagner Skis / Aug 15, 2017

29-inch Mountain Bike Wheels Versus 27.5-inch Mountain Bike Wheels

Skiers love mountain biking and at Wagner, we love getting technical with gear. The big question in mountain biking today is how to choose between a 29-inch wheel and a 27.5-inch wheel. It’s a lot like choosing between a big stable ski and a more agile mid-fat ski. The choice is personal and depends a lot on your strength, style and favorite terrain.

We reached out to Scott Turner, who is in charge of all things media and communications at Santa Cruz Bicycles, to help us wrap our heads around what mountain bike wheel size is right for you.

Perhaps you remember when 29ers first came on the scene. People were skeptical, which seems fair looking back, because at the time the 29 inch wheel was being compared to the traditional 26 inch wheel, and that seemed like a big step up. Alas, people who converted to the 29 inch wheels were hooked – they loved the smooth way the bigger wheel seemed to float over rocks and roots, and the steering stability. For some perspective, Santa Cruz came out with their first 29 inch mountain bike in July of 2009 after a few years of R&D to dial in their Tallboy geometry. It took a little over a year for the Tallboy to become their most popular model.

Fast forward a few years. In April of 2013, Santa Cruz launched their first 27.5 inch wheel option, the Bronson, and a few years later the 27.5+ wheel made its debut (the plus size tire is about 20% wider). Now bike enthusiasts have a plethora of choices, especially when wheel size is combined with suspension-travel options, changes in gear-shifting and steering geometry. Today, the company’s sales split 45%/45%/10% between 29 inch, 27.5 inch, and 27.5+ wheel sizes. So, how do you pick between a 29, 27.5 or 27.5+? Let’s start with the basics.

29 Inch Wheels

These larger wheels might be a bit less agile (that is, slower to steer), but they roll faster going along the trail. Their large diameter allows them to easily roll over features along the trail (quite like fat skis). Bikes with 29 inch wheels are often referred to as trail or cross country bikes and are ideal for longer rides covering a lot of miles and hours. They are faster in less aggressive terrain and are the preferred choice for endurance riders.

The main advantage of the 29 inch wheel is that there is more contact between the tire and the ground. This allows for more grip when cornering, braking, and climbing. The increased diameter also helps the ride feel smooth over rocks and roots.

bike tire

27.5 Inch Wheels

The smaller 27.5 wheel size allows for quicker turning, making the bike more nimble (quite like shorter, more playful skis). On the 27.5 models, you need more suspension travel to soak up the bumps, and properly designed frames have it. These bikes are ideal for more audacious riders who bike on aggressive terrain and need agility to better handle, for instance, switchback turns.

The main advantage is that the bike is designed to turn on a tighter radius. This increased responsive feel is perfect for aggressive descenders.

27.5+ Inch Wheels

These wheels are best known for their large volume. Though the wheel-rim diameter is the same as the 27.5 inch wheel, the tire is wider and deeper with more air volume inside. This gives the tire tread almost the same diameter as a 29er. These bikes offer good traction in crud-like conditions – think sand, mud and other soft slippery surfaces. Running a lower air pressure in the tires helps the tread spread out for traction and absorb bumps for a smooth ride. These bikes are designed to be playful and offer more comfort, traction, and stability without requiring increased suspension travel.

Decision Time

Turner suggests that while most people come into bike purchasing with some idea of what wheel size they want, it’s really all about fit. Santa Cruz believes in fit so much that they have a demo center back home, and a demo team that travels the country (learn more about that here). “The only cutoff for fit,” says Turner, “is that people shorter than 5’ 4” should opt out of the 29er,” which will probably be too tall.

So how does Santa Cruz ensure there is a bike that will fit your ergonomics and riding style? They are constantly coming up with ideas and looking for gaps in their lineup. Over time, most models are improved for better versatility. For example, the Tallboy began life as a cross country bike. Now, the improved bike can handle more aggressive terrain. The process starts by playing around with a design on the computer. They modify each piece of the bike, play with the variables, geometry, and placement until the bike systematically reaches a high level of handling and pedaling performance. They then head to the factory to weld the pieces together. Once the prototype is constructed, they ride it anywhere from a few days to a few weeks. Typically, it takes a few tries to get it right. They narrow down the best models and make changes until they know exactly how the bike will perform. Then, it’s off to the test lab where the bike endures destructive and fatigue testing. Once it passes the test, it heads to production.

If you still can’t decide what mountain bike option is best for you, consider doing a demo at your local retailer to dial in your best fit. Now is the perfect time to try out a handful of bike models and wheel sizes.

Want more tech on mountain bikes? Check out this article about mountain bike customization.

See you on the trail!