Recently, there have been many reports about developing control systems that actuate engines and brakes based on friction circle. We are researching the control system for motorcycles, which adds the return torque of throttle grip based on it for informing the limit of tire grip on the driving wheel. This throttle grip is a haptic display, offers haptic signals by controlling the motor connected to the throttle grip as a HMI. From the results of riding tests, the system was found helpful for riders to control the throttle grip as well as feeling easy about knowing the limit of tire grip. But it is known that the friction circle of a driving wheel depends on the normal force which changes by the gradient of road, acceleration and so on. The compensated control for changing the normal force by gradient was made to improve the throttle grip control system. The results of riding tests with the compensated system, we found that this system is important for the controls based on friction circle and it makes the haptic signals come close to the timing that riders want.