When choosing a new bike in today’s mountain bike world, riders are presented with 3 distinct wheel sizes to choose from. Our wheel experts compare the positive and negative points for each:
When a wheel contacts a bump, it takes a certain amount of effort to get the wheel to roll over the bump. The smaller the diameter of the wheel, the harder it is to get the wheel up and over the bump. The difference between a 26-inch wheel and a 29-inch wheel is only about 5 percent, but the cumulative effect of a repeated 5-percent increase in effort multiplied by every bump encountered (thousands of times in a mile) adds up quickly. As a result of this, the larger-diameter 29-inch wheel has noticeably less rolling resistance than its 26 inch counterpart.
Another benefit of a larger-diameter wheel is the relationship between the bottom bracket center and the wheel axles. A lower bottom bracket lowers the center of gravity and gives the bike a more stable feel while cornering. The bottom bracket heights of 26, 27.5, and 29-inch designs are about the same, but the center of the hub axles on larger wheels is proportionally higher. Weighting the pedals of a 27.5 or 29er puts much of the rider's weight below the wheel/hub axle height, which has a profound stabilizing effect.
Pros vs. Cons
26 INCH WHEELS
Excels on steep and technical climbs. Best acceleration. Braking is strongest, especially at the bottom of steep descents. By far the most responsive to pumping the trail. The lightest setup when all other factors are equal. Best strength to weight ratio, resulting in better durability.
Descending not as confidence inspiring, especially after spending time on the other two wheel sizes. This bike requires more rider input and a bigger commitment. While 27.5s and 29ers can “roll” a technical section with their larger wheels, the 26 inch bike needs to maintain enough speed to stay on top of the ruts, rocks and roots. The rider has to work harder to descend as well.
Most common/popular usage: Downhill Racing, Freeride, Dirtjump, Slope Style, Dual Slolam
The bikes tend to have a “flickable” feel that is closer to the 26 inch models than the 29ers. Your body position always feels neutral. You can pump the 27.5er along the trail almost a easily as a 26 inch bike and when the trail heads downward it allows the rider to remain relaxed. These wheels do a good job of staying on top of the rough stuff and the front end goes where you want it to go.
27.5s don’t steer as fast as a 26er. They don’t roll over the rough sections as smoothly as a 29er. Component selection is currently somewhat limited but more tires, wheels and forks are becoming available as this size gains popularity.
Most common/popular usage: All Mountain, Enduro, Trail
The big wheels are great for descending. They smooth out rugged trails that would be a chore on a 26 inch wheel model. The added confidence inspires you to remain more relaxed as the wheels float over rough terrain. With the largest contact patch, 29ers have the best traction of the bunch, both in corners and on long gradual climbs. Although 29ers have the slowest acceleration of the 3, once up to speed, the bike holds momentum well.
29ers don’t steer as fast as a 26er. Accelerating up to speed takes longer than 26 or 27.5. Steep climbs are more difficult. The large wheels don’t respond as well to pumping the trail. In some cases, 29ers may require larger brake rotors to maintain adequate stopping power. Wheel strength and stiffness are not on par with the smaller wheels at similar weights. Smaller riders may have difficulty finding a good fit on a 29er.
Most common/popular: Trail, Cross Country