Over the years, mountain bikes have evolved from a non-suspension pedal-powered vehicle with large tires to a sophisticated trail-riding machine. During this evolution, front forks with suspension absorbed bumps, giving you greater control over rough terrain. Then the frame was split, given a pivot point and a shock absorber to further increase your control. The 29-inch tires, also known as the "29er," is the next step in mountain bike evolution.
The larger diameter of a 29er allows for a wide contact area with the ground, when you encounter air-down situations like loose dirt, sand or mud. This is due to the larger sidewall of the 29-inch tire compared to its smaller counterparts. Even when inflated to its recommended PSI, the larger contact area of the 29er increases your traction when cornering or climbing uphill in any condition.
Path of Least Resistance
A larger diameter tire requires less resistance when rolling than a small wheel. This translates into an easier ride over both a trail or on the way to the trail. An easier ride conserves your energy; that is a valuable advantage to have when planning on heading out for an all-day adventure with your mountain bike.
When you look ahead and see a steep hill climb approaching, don't despair -- the 29-inch tires on a 29er will help keep your forward momentum as you reach the incline. This increased momentum requires less preparation before you hit the hill and results in less speed lost as you climb longer inclines. This helps conserve energy during your ride.
Trail Riding Rewards
During your ride you’ll encounter bumps, ruts, tree roots and a host of other obstacles that have the ability to catch your front wheel. Catching a wheel often results in flipping your bike or at least losing control and sending you off the trail. The larger diameter of a 29-inch wheel allows it to cross most obstacles -- that would normally catch a 26-inch wheel -- without causing you to lose control. This is due to the higher attack angle of the larger tire, meaning the obstacle hits the tire at a higher point than a smaller wheel. Fewer wrecks, of course, make for a more enjoyable day on your bike.
A 29-inch tire has 1 1/2-inch more height than a 26-inch tire. This makes the larger frame required for the larger tire a better fit for taller riders who would otherwise feel awkward and clumsy on a smaller 26-inch mountain bike frame.