# Comparison of Achieved Rolling Resistance Values of Two Selected Tires on a Solid Surface
## 1 Introduction  
The main component of the loss resistance of vehicles and mobile work machines with wheeled chassis in forestry is rolling resistance. A significant part of their movement is often carried out on public roads or on paved surfaces of forest roads. The flexibility of these surfaces is very small and therefore the deformation of the tires is mainly applied at these places. This significantly affects their final value of rolling resistance and the overall driving energy efficiency on a paved rigid surface. It is well-known that lower tire inflation pressures can be used on forest soil in the stand to improve throughput and reduce compaction of the stand soil. This is partially an advantage over crawler vehicles, where the resulting contact pressure on the soil depends on the used construction of the vehicle mechanism [1]. The correct choice and use of suitable tire inflation pressures is important not only from an environmental point of view, but also from an economic one. The correct choice of tire inflation pressure significantly affects the passability of the terrain and affects the overall life of the tire. This work is focused on measuring rolling resistance on a solid surface, which is not possible to demonstrate in forest conditions; however, in this paper, it is indicated that the right choice of tire inflation pressure on the surfaces forming a part of the road surface in forestry is essential and it cannot be underestimated. At present, there are technical means by which it is possible to achieve a change in the inflation pressures of the wheels relatively quickly and without a great physical load on the mobile mechanization means. These systems are called Central Tire Inflation System CTIS. The significant issue in this direction is also the choice of the right fitting of mechanization means, especially a suitable choice and selection of the type, construction, size and load capacity of tires for individual wheels. According to [PERSON] [2], with this choice and application of the CTISsystem, it is possible to pass up to 10% of terrains that were previously unavailable for mechanized vehicles with wheeled chassis. Rolling resistance can be defined as the energy loss caused by the rolling of a tire and its imperfectly elastic deformation, as well as the springing of the tire [3]. As reported by [PERSON] et al. [4], of the total CO\({}_{2}\) emissions produced annually in the USA, up to 29% is accounted for by the transport and relocation sector of mobile work machines, which takes place on solid surfaces. This percentage is not negligible, so reducing the rolling resistance of the tires used in these vehicles is an important task. The tire deforms by the action of vertical (radial), circumferential and lateral forces during driving [5]. When the tire is loaded with a vertical force (the weight of the vehicle), the part of the curve of the running surface of the tire (tread) which meets the road surface must be compressed to a certain length. After turning the tire, a part of the running surface is lightened, so that the part of the rubber which was previously compressed expands. In a similar way, the running surface deforms in the transverse direction. After unloading, the rubber particles expand. In this way, the tire particles are alternately compressed and expanded in a circumferential and transverse direction by a certain frequency depending on the speed of the wheel, and thus also on the speed of the vehicle or machine [6]. The deformation work caused by the action of the mentioned vertical, circumferential and lateral forces does not return completely after the tire is relieved. Part of the work is focused on overcoming the hysteresis losses of the tire. According to [PERSON] and [PERSON] [7], the cause is the imperfect flexibility of the tire, which does not completely return to its initial state due to its own damping after unloading. The rolling friction resistance is related to the work for overcoming tire losses.