Dunlop 45170002 Geomax AT81 Front Tire - 90/90-21 Newly formulated high-wear-resistant rear tire compound offers enhanced chipping, tearing and wear appearance. Geomax AT81 rear tire carcass features two nylon plies. Lateral grooves on the shoulder knobs provide additional biting edges and also allow the knobs to be more flexible. Rear center blocks are arranged in-line to provide a larger contact patch for maximum traction. Dunlops plush pad recess design between tread blocks enhances compliance for bump absorption and ride comfort.