In road bicycle races, advanced skills are needed to traverse downhill corners quickly and safely. A previous study revealed that in specific experimental corners, some beginners tend to lean their bikes more compared to experts. Therefore, in seeking to develop a support method for improving rider skill in controlling bike position, the authors aimed to design a system that indicates to users the positions of their bikes to lean it at the appropriate inclination when making turns. First, we determined the corner starting points using the RTK (Real Time Kinematic) positioning system. Then, we calculated the theoretical inclination and compared this to the inclination practiced by an expert. The experiment with this system showed that the expert started leaning the bike approximately 5 m short of a corner’s starting point with the speed maintained at approximately 25 km/h, with some correlation found between the theoretically ideal degree of inclination and the expert’s actual inclination.