
A 29er frame is designed to accommodate 29 inch wheels. These larger wheels are becoming more popular among cyclocross riders as well as single speed riders and larger cross country mountain bikers. The frames have to be slightly different than regular to accommodate the larger wheels which often add weight, but it allows the rider to roll over obstacles easier and faster.
A 29er frame is great for larger riders who can handle the larger wheel size. Although it is heavier, the wheels are often stronger making them last longer and they look like a regular size bike under really tall and large people. A regular sized wheel looks very funny on a bike designed for someone six and half or seven feet tall.
A 29er frame can be found fairly easily because of their increasing popularity. They are also known as 700mm set ups. Since the wheel is larger it is easier to roll over larger obstacles (known as the angle of attack) and there is more tire traction for all purposes but it is most significantly felt on climbs and when braking.