
A 29er frameset can easily accommodate 29 inch wheels and 700C tires. This is the standard for road, touring and cyclocross frames because these larger wheels roll easier and faster although they are more difficult to get up to speed. This is why they are rarely used on mountain bikes.
A 29er frameset for a mountain bike is less common than for road bikes because of the difficulty in changing speeds but they are becoming more popular among larger riders and professional cross-country riders that have the extra skill and power to successfully maneuver the larger wheels. They retain their speed better and roll over larger obstacles.
A 29er frameset gives the rider a higher view of the trail or road and can be constructed with the same methods as other frames making them comparable in cost. They are typically heavier and more robustly built than smaller frames to accommodate larger riders and higher speeds.