An off-road vehicle speed control assembly that includes a speed control device, a speed sensor, tire pressure sensors and an electronic controller. The speed control device controls speed of a vehicle power plant. The electronic controller is in electronic communication with the speed control device, the speed sensor and the plurality of tire pressure sensors and is configured to operate the speed control device in at least two different modes of operation: a normal mode in which the plurality of tires are inflated to a high-speed tire pressure; and, a first off-road mode in which the plurality of tires are inflated to a first off-road tire pressure that is less than the high-speed tire pressure. In the normal mode, speeds of the vehicle are unrestricted by the electronic controller. In the first off-road mode, speed of the vehicle is restricted.