Each Challenge Tyre is a hand made work of art, with the company producing some of the lightest wide profile tyres available. The Gravel Grinder tyre is designed to withstand the constant assault of a gravel road for hours on end. Created to inspire off road confidence, the knobs of tread on the edges of the tyre hold tight to the ground where other tyres have long slid out, and the low profile centre decreases rolling resistance for efficient pedalling.