An unpaved, usually outdoor surface is considered off-road to an RC vehicle. Off-road surfaces include loose or packed dirt, grass, unpaved or extremely rough roads, and rocky or uneven terrain.

RC vehicles such as 4x4s, dune-buggies, and monster trucks that can handle rough terrain and do not have to stay on a paved surface are off-road vehicles. They may also be called all terrain vehicles because they can drive both on-road and off-road. They typically sit higher off the ground than on-road vehicles, have knobbed or grooved off-road tires and are built with tougher suspensions and drivetrains so they can drive and race on dirt and grass, climb rocky hills, and jump over obstacles.

Outdoor tracks for off-road RC vehicles are usually dirt tracks with a variety of jumps (dirt ramps) and bumps or moguls.

Electric models

Electrically powered models utilize mechanical or electronic speed control units to adjust the amount of power delivered to the electric motor. The power delivered is proportional to the amount of throttle called for by the transmitter - the more you pull the trigger, the faster it goes. The voltage is "pulsed" using transistors to produce varying output with smooth transitions and greater efficiency. Electronic speed controllers use solid state components to regulate duty cycle, adjusting the power delivered to the electrical motor. In addition, most electronic speed controllers can use the electric motor as a magnetic brake, offering better control of the model than is possible with a mechanical speed control. Mechanical speed controllers use a network of resistors and switch between them by rotating a head with an electrode around a plate that has electrical contacts. Mechanical speed controllers are prone to being slow to react because they are actuated by servos, waste energy in the form of heat from the resistors, commonly become dirty and perform intermittently, and lack a dedicated braking ability. They are less expensive than high performance electronic speed controls and usually ship in older hobby-grade models. They are gradually being phased out. Most electric cars up to recently used brushed motors but now many people are turning to brushless motors for their much higher power and because they require much less maintenance. They are rated either in relative turns or Kv. The Kv number tells how many RPM the motor will turn per volt, assuming no load and maximum efficiency. However, the ability of the system to put out power is dependent on the quality of the batteries used, wires and connectors supplying power. A well wired brushed system can outperform a poorly wired brushless system in many cases. Due to their power, brushless motors are also used in bigger monster trucks and 1/8 nitro-powered buggies that have been converted to electric. Some 1/5 scale gas to electric conversions are in production but are uncommon due to high price.

 

Nitro-powered models

Nitromethane fuel powered models utilize a single servo for throttle and braking control; rotation of the servo in one direction will cause the throttle on the carburetor to open, providing more air and fuel mixture to the internal combustion engine. Rotation of the servo in the other direction causes torque to be applied to a linkage and cam which causes friction with the braking material. The brake is commonly located on the driveshaft or spur gear in some cases and applies stopping power only to the driven wheels. Some models will also use an additional servo to control a transmission box, enabling the vehicle to drive in reverse.

Fuel engine sizes most often range between .12-.35 cubic inches. Engine size is related to the class of car; 1/10 scale on and off road vehicles usually are equipped with .12-.18 cubic inch engines, with 1/8 scale vehicles using .21-.32 cubic inch engines. "Ready-to-run" cars can be purchased, which leave the factory in a pre-tuned condition that affords for good racing performance without prior adjustment. Alternatively, vehicles can be purchased that are either in kit form or are partially assembled, which are built and tuned by the owner prior to use, but most of the time, the owner will have to buy radio gear, and sometimes even an engine when they buy a kit.