This is the popular, fast rolling Surly Knard 29er Plus Folding Mountain Bike Tire. What’s 29" It’s a tire meant for rims with a bead seat diameter of 622mm (29"), but large volume and ideally shaped when used on a very wide rim. In this case Knard is a 3" tire designed for 50mm rims. The larger diameter smooth’s rolling over rough ground, the increased volume adds a bit of suspension and float, the width increases traction, and the sheer size holds speed well. The profile is round and tracks well cornering and off-camber, and will remain effective on rims as narrow as 35mm. The closely spaced low-block tread grips well on multiple surface types but is most at home on dry rock and packed dirt.