45NRTH Kahva Tire - 27.5 x 2.1 Tubeless Folding BLK 60 TPI 240 Concave Carbide Studs45NRTH Kahva Tire 27. 5 x 2. 1 Tubeless Folding Black 60tpi 240 Concave Carbide Studs. From light winter trail riding to commuting the Kahva allows you to carve your way through winter with concave carbide studs as well as single double and triple siped lugs. Siping on center and side lugs lets the Kahva conform to terrain for increased grip in any riding conditions Concave carbide studs provide traction in the iciest conditions Directional lugs