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This generally refers to the upper and lower suspension arm of a vehicle; the arm’s 2-point chassis hinge and single point mount at the hub resembles the letter “A”.

After-Run Oil
Just what it sounds like. After you’re done running your nitro engine, it’s recommended that you remove the glow plug and place a couple of drops of After-Run oil in the cylinder as well as in the carb throat.

Air Dam
To prevent a car from lifting off the track at high speeds, most touring car bodies have an extension or air dam in the front bumper that is designed to keep air from getting under the car.

This refers to the angle of caster on the rear wheels. Raising the front of the hinge pins of the rear arms gives a caster (anti-squat) angle and helps to transfer the power more evenly, keeping the front of the vehicle from lifting under heavy acceleration.

Ball Cup
This is a “cupped” plastic piece that snaps onto a ball end to provide a pivot point—usually for suspension movement. Using this type of assembly instead of a rigid system allows the cup to pop off in the event of a crash, instead of breaking. Using turnbuckles with ball cups allows for more tuning flexibility.

Ball End
The ball end is a metal ball with a hex and screw threads on one end. A ball cup attaches over the ball end to provide a pivot point.

This is essentially a metal “donut,” with tiny balls inside which permit rotating shafts to spin more efficiently. Bearings are widely considered to be the first upgrade necessary for any kit that includes bushings.

BEC (Battery Elimination Circuitry)
Built into an ESC, this circuit uses an electric vehicle’s main battery pack to provide power to the radio equipment, without the need for a separate receiver pack.

Steering mechanism used in most RC vehicles that consists of two posts joined a link. Each is connected to a left or right steering knuckle with a turnbuckle with one post connected to the steering servo.

Big Block
Refers to engines that are .21 size or larger and .15 size engines that use the engine case of a .21

When building or rebuilding shock absorbers, it is necessary to remove all of the air and any excess oil. This is known as bleeding the shocks.

Blue Groove
This term refers to dirt tracks that have been smoothed out and packed down along the optimum racing line over time. A blueish tint results from tire wear.

Body Reamer
The body reamer is a must-have tool for creating perfect body post holes in Lexan bodies and other semi-soft materials.

A new nitro engine has to go through a break-in procedure to mate the engine’s piston to the cylinder sleeve. This provides a longer life expectancy between rebuilds. Recommended procedures will vary by manufacturer and engine. Generally, an engine will need to be run rich and at no more than half throttle for the first 2-3 tanks of fuel. The entire procedure can consist of anywhere from 3-5 tanks of fuel, depending on the individual engine’s instructions.

A very fundamental part of your R/C vehicle. Several major components rely on the bulkhead to join them to the chassis. Shock towers, upper chassis plates and suspension arms. Differentials are sandwiched between the left and right bulkheads.

A metal, and sometimes nylon, “donut” that supports a rotating shaft (like an axle). Most metal bushings are made out of something like Bronze Oilite, a metal that is permanently lubricated.

This refers to the angle of the tires in relation to the ground, as seen from the front and rear of the vehicle. Zero camber (90 degrees) refers to tires that are exactly perpendicular to the ground. Tires leaning toward each other have negative camber, while tires leaning away from each other have positive camber. A general rule of thumb is to have a slight bit of negative camber and to be sure both tires maintain the same camber angle. For the most part you should always avoid positive camber.

This can also be referred to as a carb. This part of the engine controls the ratio of fuel and air entering the engine. There are two types of carbs: slide carbs, where the barrel slides along its axis instead of rotating; and rotary or barrel carbs that rotate. The rotary carb is most common among RTR kits and is fine for most applications. The slide carb provides a quicker response and is therefore more desirable to the more serious enthusiast.

Center of Gravity (CG)
The higher your chassis components sit above your wheel’s axles, the higher the CG of your vehicle. As a result, it may roll over more easily during tighter turns. Keeping your CG as low as possible will provide a more stable vehicle.

Made from aluminum, plastic composites or woven carbon fiber, this is the main platform to which all other components attach.

Clutch Bell
The clutch bell attaches to the crankshaft of a nitro engine and meshes with the spur gear, performing the same function as a pinion gear on an electric motor. Changing the number of teeth on a clutch bell alters the way a vehicle performs. Fewer teeth produce more low-end torque, whereas more teeth increase top-end speed.

Clutch Shoes
Clutch shoes are made from aluminum or a composite material and are attached to the engine flywheel. They expand under increasing RPM to engage the clutch bell that, in turn, engages the spur gear to make the vehicle move.

Crank Shaft
The shaft that the flywheel and clutch bell are mounted to. It is attached at the back to the piston by means of a connecting rod. The up and down motion of the piston causes the crank to rotate.

Abbreviation for Constant Velocity Drive. A type of drive shaft that uses a ball type set up that functions similarly to a universal drive shaft. Although “CVD” is a trademark of MIP (Moore’s Ideal Products, Inc.) it has become commonly used to describe any drive shaft of this type.

The rate at which a shock is compressed or rebounds. Most RC kits now contain shock absorbers that are filled with fluid/oil. Without this fluid, the shocks are bouncy and provide very little benefit where control is concerned. By changing the weight of the oil or the type of shock piston, or both, you can change the damping rate to tune your car to a specific track and/or driving style.

A differential is a unit that transfers power from the input to output shafts. The differential, or “diff,” enables the outside wheel of a vehicle to spin faster and travel farther than the inside wheel during a turn.

Many battery chargers include a built-in discharging function.

A metal driveshaft with a ball at each end that has a pin going through the center; the pin fits into a slot in the outdrive to transmit drive train power.

Drag Link
A bellcrank steering systems consists of 2 posts connected by a bar. This bar is the drag link and is also referred to, by some, as Ackerman link.

Dual Rates
This refers to a switch that regulates the sensitivity of transmitter control input. This is a useful function for many beginners, who tend to over-control their vehicles.

Short for dynomometer. A device used to rate and compare electric or nitro engines. It measures things like RPM, torque, HP, efficiency, power, amp draw and some will provide powerband graphs.

ESC. Electronic Speed Control
An electronic component that controls throttle input by regulating the current being sent through the motor.

Exponential Rate
This refers to servo travel that is not directly proportional to the degree of control input. A negative exponential rate makes the control response milder around the servo’s center point, but it becomes increasingly stronger as the input approaches 100%.

Fail Safe
If the transmitter’s signal is lost or interrupted a fail safe unit returns the servo to a predetermined position to avoid dangerous runaways. A battery failsafe is a safety feature which brings the throttle servo down to idle as a warning that the receiver battery’s voltage is getting dangerously low.

Fixed Link
Camber and steering links on many RTR (ready to run) vehicles use a non-adjustable link. These can usually be upgraded with turnbuckles as the driver’s skill improves, as he is looking for more adjustability.

The flywheel is the larger metal wheel that sits behind the clutch bell and aids the engine’s crankshaft with momentum and idling. For more torque and smoother idle use a heavier flywheel; for improved top speed and throttle response use a lighter flywheel. On non-pull start models it also represents how to start the engine with the use of a bump starter or starter box.

Foam Inserts
These inserts are used inside tires to help them retain their shape. Different densities are available for use on different track surfaces.

Fuel Gun
A rapid fuel delivery system used during nitro races. Generally speaking, they deliver 75ccs of fuel in just a second or two.

Otherwise known as radio interference, a glitch refers to a momentary lapse in signal transmission. There are external sources that cause glitches, (like overhead power lines,) but consistent glitching is most likely the result of something in the vehicle itself, such as metal-to-metal rubbing as you might find with control linkages.

Glow Plug
Resembles a miniature spark plug. A glow plug supplies the necessary heat for igniting the fuel/air mixture in an engine. A battery-powered unit sometimes called a glow starter is installed over the plug to heat the small wire filament inside the chamber. After the engine is running, the glow starter can be removed since the wire filament inside the plug is kept hot by the engine’s “explosions within the chamber.

This is the aluminum exhaust coupling that attaches to the engine’s exhaust port. A muffler or tuned pipe is usually attached to this bent piece of aluminum tubing.

Hinge Pin
This is a straight metal pin that connects the suspension arm to the bulkhead, and it allows the arms to pivot up and down.

Hub Carrier
This housing supports the drive axles of a vehicle, and uses bushing or bearings to keep the shaft turning smoothly.

Hydraulic Lock
Also know as hydra lock, the term refers to when the engine becomes flooded with fuel preventing the piston from compressing in the combustion chamber. Engine damage can result if the crankshaft is forced to rotate without relieving the pressure. If this happens remove the glow plug, turn the vehicle upside down and briefly crank the engine to drain the excess fuel


A car, truck, boat, airplane or heli that requires the modeler to do most/all of the building and finishing work. Modelers are likely required to add their own servos, power plant, and radio system.

When the needles on the carburetor are set such that the engine is not getting enough fuel, this is referred to as running lean. Running too lean may help fuel economy and appear to make the vehicle run better; however, it is also a sure way to shorten the life of the engine.

This is a clear, plastic-like material that is vacuum-formed over molds to create different body styles. These bodies are then painted on the inside so that the paint does not scratch off from less than perfect laps around the track.

 Linkage (throttle, brake)
Heavy gauge wire is used to connect servo horns to throttle and break controls.


Lithium Polymer Battery. Currently the most common type of ‘expertise upgrade’ battery, these are more powerful and efficient than the entry-level NiCd and NiMH batteries, but also more complicated and dangerous to run. They pack more power into a smaller space, thus making them more attractive but also more volatile. They are marginally safer and lighter than their LiFe predecessors, however, with a higher energy density.Must be used with a LiPo-compatible balancing charger.

A nut that uses a nylon insert in order to better grip the threads of a bolt or shaft and thereby preventing it from coming loose. It is used extensively for axles and other areas where nuts must stay secure, but it may need to be removed frequently for maintenance or repair.

Marshall (Turn Marshall)A racer who, after he has finished his race, stands at various spots around the track during the next race to turn over any vehicles that have flipped and to remove vehicles that are no longer operable, for whatever reason, from the race course.

(mAh) This is a rating for batteries. The higher the milliamp rating, the longer the cell can provide power. Currently, most RC batteries range from 1500 to 3300 milliamp hours.

 Module used to describe the tooth pitch of a metric pinion or spur gear
The most common modules are 1.0, .8, .6, and .4.

All nitro-powered cars use some type of muffler to reduce the noise output and provide pressure to the fuel tank.

Needle Valve
A nitro engine can have from one to three adjustment needles on the carburetor. They are used to adjust the air to fuel ratio. On most engines, the needle is turned clockwise to lean the mixture (allowing less fuel and more air to enter,) and counterclockwise to richen (permitting more fuel and less air to enter.)

NiCad (or NiCd)
Rechargeable Nickel Cadmium batteries, most commonly used to power radio transmitters and receivers. Also used in stick packs in electric vehicles.

Nickel-Metal Hydride (Ni-MH)
Battery cells that do not have “cell memory” with slightly less voltage than nickel-cadmium batteries. For the average enthusiast this means less maintenance.

This is a fuel additive that increases a model engine’s performance. The ideal nitro content (measured by percentage) varies from engine to engine, but you will typically find 10 to 30 percent on the hobby shop shelf.

One-Way Bearing
This is a bearing that allows a shaft to turn in one direction only.

The outdrive refers to shafts that exit the differential on either side and transmit driveline power to the drive wheels using an axle shaft or universal.

The condition that’s usually present when the rear wheels lose traction before the front wheels ending up with the rear of your vehicles swinging around through turns. Adjusting shocks, stickier tires or more rear down force are some possible solutions.

Peak Charger
When the battery has peaked, meaning it will no longer accept a charge, this type of charger reverts to a maintenance charge rate, considerably decreasing the chance of damage to the pack.

The point at which a battery no longer accepts a charge. Energy is then converted to heat that is potentially hazardous and can be damaging to the battery pack.

Pinion Gear
Electric RC vehicles use a pinion gear attached to the motor’s shaft to turn the spur gear which in turn spins the rest of the drive train.

The piston fits into an internal cylindrical part of an engine called a sleeve and slides up and down during the combustion cycle. The piston turns the engine’s crankshaft via a connecting rod, converting the energy of combustion into rotational torque. The piston and sleeve of an engine are replaceable but must both be replaced at the same time.

In its simplest terms, this refers to the size of a gear’s teeth. For instance, a 32-pitch pinion gear has larger teeth than a 48-pitch gear. The number represents how many teeth per inch.

Power Supply
A device that converts 110VAC to 12VDC. Generally used to power charging equipment. · Preload (shock). Adjusting preload on shock absorbers determines a vehicle’s ride height. It is adjusted either by clip-on spacers or by tension clamps. Threaded shock bodies use a metal ring that is rotated up or down to adjust preload.

A full-scale working model of an original new product or an updated version of an existing product.

If a vehicle’s front tires don’t provide enough grip through turns the car will not turn as sharp as it should. It will appear to go straight even though the wheels are turned.


Remote Control Gas and Electric Auto Racers Society

Receiver (Rx)
The servo and ESC plug into this electronic unit in an RC vehicle. The receiver converts the radio signals from the transmitter into servos and/or electronic speed controls commands.

The resistor is the ceramic unit on an electric vehicle’s mechanical speed control (MSC) that limits the amount of current transferred from battery to motor. It dissipates the energy as heat.

Reverse Lockout
This is an ESC function that prevents accidental engagement of reverse function on an ESC. Reverse is generally not permitted in organized racing, in order to prevent track mishaps.

When the needles on the carb are set such that the engine is getting too much fuel it is referred to as running rich. If you accelerate from a stop and the engine dies, you are probably running too rich and should lean out the engine’s low speed idle adjustment a little (by turning the needle valve or low-end adjustment slightly clockwise).


Abbreviation for “Remotely Operated Auto Racers”. Is a set of guidelines/rules for racing and is normally used as a stamp of approval for products.

Measurement of engine speed; the number of rotations/revolutions per minute.

RTR (Ready to Run)
Some cars and trucks are available pre-built and will be indicated by the term RTR (Ready-To-Run). The RTR vehicles cost a little more but typically come with everything you need (except a battery and charger). If you’re not interested in building your car, this is an option for you.

Total length of time a vehicle will run on a single battery pack or tank of fuel.

Sand Bagger

Term used for a racer running in too low of a main or class. Either because they broke in a qualifier or because they are to chicken to run with people of their same ability level.

Servo Reversing
This is just what it sounds like. Radios with this function allow the user to reverse the output of the servo. This is useful when you switch the radio system between vehicles that may use different servo placement or orientation.

This is the unit that actually does the physical work inside your vehicle. A servo contains a small motor that, when activated by commands from the transmitter, moves the control linkages for steering, throttle and brakes. Some vehicles with 3-channel radios have a third servo to activate other functions, such as reverse or shifting of gears.

Servo Saver
A device that protects the servo from excessive force that could damage its gears. It can be integrated into the control horn or the steering bellcrank.

Shock Piston
A small plastic, brass or nylon disk that travels up and down inside an oil-filled shock body. It uses a hole or holes to regulate the rate at which the shock compresses and rebounds.

Skid Plate
A plastic or metal (usually aluminum or titanium) plate that protects the underside of off road vehicles.

The internal cylindrical part that houses the piston in a nitro engine.

Slipper Clutch
This refers to a device found primarily in off-road vehicles that allows the spur gear to slip under excessive load. This feature protects the driveline from excessive wear and, when set properly, makes it easier to drive in loose conditions.

Spur Gear
The large gear that meshes with a pinion gear or clutch bell to provide power to a vehicle’s drivetrain.

the difference between the circumferences on the left and right side tires. In oval racing, a positive stagger means the outside tires are larger than the inside.

The small tubular tip on the side of a tuned pipe where exhaust is expelled.

Sway Bar
A heavy wire that attaches across either or both the front and rear of a vehicle’s suspension arms. It is designed to keep equal down pressure on the left and right through turns. When the outside edge of the vehicle is pushed up through a turn the sway bar pushes down on the inside edge to keep the tires on the ground.

Synthesized Receiver
A Receiver, utilizing crystal-free technology, that can be set to any desired frequency.

Tamiya/JST Connectors
These electrical connectors are widely used within the hobby. The shape of the female end on the battery and the male counterpart on the electrical component prevent accidental reversing of the polarity, which would create a short circuit.

Tire Truer
On-road racers running foam tires are likely to have a truer in their pit boxes. When the foam donuts become worn or damaged, the surface can be renewed with a tire truer, a machine that operates in the same manner as a lathe.

Toe Angle
When seen from above, a car’s front wheels will point inward when the steering trim is set to neutral. Applies to the rear wheels as well. This provides some degree of stability. Too much toe angle will slow you down.

TQ. Top Qualifier
The driver who turns the most laps in the shortest amount of time. In full scale racing this is known as the pole setter.

Traction Compound
A liquid substance applied to tires to enhance traction.

The part of a radio system that is used by the driver to control a vehicle. The transmitter sends signals based on a drivers input to a receiver that is mounted in a vehicle.

This is a small electronic device mounted in a race vehicle. It transmits a signal to a receiver located at the start/finish line. The receiver records a vehicle’s position and lap times during a race for scoring purposes.

Tuned Pipe
This is an upgrade for any vehicle equipped with a muffler. It is designed to increase an engine’s power output. Different tuned pipes are available for different applications. Some provide increased top end speed while others provide bottom end power.

This is an adjustable link that has conventional threads on one end and reverse threads on the opposite end. This enables you to make vehicle adjustments without having to remove the link from a vehicle completely.

Universal Dogbone
A universal dogbone is a driveshaft that combines a conventional dogbone and axle into a single, more efficient unit.


Wide open throttle. Applies to both nitro and electric models, although on electric models it is somewhat figurative. It just means that the throttle is at full.

Zip Tie
A term commonly used for plastic cable wraps because of the zipping sound it makes when tightened. A good pit box will always have several sizes buried among the hex wrenches and dead glow plugs.

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