Do You Need A 29er Mountain Bike?

29er mountain bikes have 29-inch wheels.
29er mountain bikes have 29-inch wheels. Jordan Siemens/The Image Bank/Getty Images

If you've been in touch with mountain bike industry trends over the years, you've probably noticed that the 29-inch-wheeled bikes that came out a few years back haven't really gone away. In fact, they've multiplied. These days, you'd be hard-pressed not to see one on your local trails. So, what caused the 29er trend to stick around? Who benefits from these bikes? Should you switch to bigger wheels yourself? All good questions. The answer really depends on you and the type of riding you want to do.

The Origin of 26-Inch Wheels

Interestingly enough, the 26-inch wheel standard has somewhat arbitrary beginnings. The size of the wheels and tires used in the early days were used simply because 26 inches was a convenient size found on adult and cruiser bikes of the time (the earliest mountain bikers blazed down mountainsides in California on slightly modified cruisers). Even so, one may argue that those 26-inch wheels of the day were that size for good reasons.

Big-Wheeled Benefits of 29ers

There are certainly benefits to 29-inch wheels over the standard 26 inchers. First, they have less rolling friction. This means that once they are up to speed, they roll more efficiently and maintain momentum better than smaller wheels. Second, larger wheels -- and their larger tires -- have more ground contact. As mountain bikers know, more tire on the ground means better traction. Also, larger tires allow for slightly lower air pressure (when that's desirable), which further increases ground contact.

Perhaps the biggest benefit of 29ers is that they offer better obstacle rollover. When met with the same size of obstacle, the obstacle hits a larger wheel at a lower point than a smaller wheel, making it easier for the larger wheel to roll over the obstacle. In other words, the obstacle is literally smaller relative to the wheel size. If you spend a lot of time flying over boulders and monster logs and roots, this benefit might be a deal-clincher.

Finally, 29er mountain bikes are taller than standard bikes. If you're tall, this is a clear benefit. Of course, if you're a shorter rider, this might be more of a drawback.

Big-Wheeled Drawbacks

The big wheels on 29ers have greater rotating mass -- more of the wheel's weight is farther away from the hub -- resulting in slower acceleration, particularly from a standstill. The flip-side of this is that once you get up to speed on a 29er, the larger wheels roll more efficiently. You can think of it this way: small wheels are faster off the line; big wheels are faster at cruising speed.

Larger wheels weigh more. How much is hard to say, but some bike retailers suggest that the weight penalty can be up to 2 pounds for the larger-wheeled bikes. A tiny portion of the penalty may be incurred by the larger frame components, which leads us to the next potential drawback...

...29er mountain bikes have a longer wheel base, making them feel less maneuverable than 26ers. If you like a really, tight, responsive bike with super-quick steering, you might not be crazy about the handling of a 29er.

And finally, back to the height issue. Larger-wheeled bikes usually have a higher standover height. For shorter riders (say, 5' 6" or shorter), it can be harder to find a really good fit in a 29er.

Nothing Like a Mountain Bike Test-Drive

You can read about the differences between 29-inch and 26-inch mountain bikes all day, but the only way to really know the difference is to demo some bikes of both sizes. Good bike shops host demo days throughout the year, and many have demo programs that let you "rent" bikes for one or more days anytime. This allows you to demo bikes on your favorite local rides so you can see how they perform under the conditions you ride most often. Demo programs can be pricey, but the cost usually can be applied to any new bike at the store. So if you like the shop it's a pretty safe bet.