New sizes of the K28 Because of the very good experiences with the 4.00-18 K28, which is OEM-fitted on the Ural Retro, we made the decision to manufacture size 4.00-19 K28 for motorcycles with sidecar as well. The big footprint allows an optimized distribution of the driving force and a reduced abrasion. Further on, the new tire structure is designed to transfer the steering thrusts of the sidecar to the road surface and to ensure a good handling and braking behavior. As of spring 2015, the tire can be obtained from the market.