RC Glossary

RC glossary of the key terms related to RC cars whether off-road, on-road, or oval. Get ready for any RC car race!

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- # -

2.4 GHz

A long-range radio frequency used by the transmitter and receiver. Modern 2.4 GHz radio systems are programmed to a specific RC car and should not interfere with other RC cars in the vicinity.

- A -


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


The degree of difference in the steering angle between the inside and outside wheel when a vehicle is turning.

ATV / Adjustable Travel Volume

ATV allows you to preset the maximum travel of a servo to either side from its neutral position. Such settings help adjust control action to suit your driving style. Also known as ATV.

Adjustable trim rate

If you’ve ever wished you could set how much servo movement you get with each “click” of trim, this is the function you want. By adjusting the trim rate, you can set the percentage of travel each click of trim represents.

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

An extension of the front bumper that blocks, or diverts, air around the car instead of under i 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.


Amplitude Modulation. Most RTR or ready-to-run kits come with an AM radio system, which is suitable for most newcomers. More serious racers will opt for FM or PCM radios that are less prone to glitching.

Anti-lock brakes (ABS)

The ABS function is invaluable when racing on slippery surfaces or when running cars with rear-wheel braking only. When ABS is set, applying the brakes will cause the servo to pulsate or to quickly engage and disengage the brakes for smoother, more controlled braking. Most ABS systems allow you to set the delay (the time it takes for the ABS to engage), the depth (the total travel of the servo during pulsing) and the speed (the rate at which the servo pulses back and forth).

Anti-Roll Bar

Anti-Roll Bars link the left and right sides of the car together (attaching to the suspension arms). Their purpose is to help prevent body roll through the corners. A thin bar allows more body roll, a thick bar prevents body roll. This is a useful tuning tool for on-road cars on flat, high traction surfaces. Also known as an Anti-Sway Bar.


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 RC car from lifting under heavy acceleration and keeping the rear suspension from squatting (compressing) under acceleration.

Anti-Sway Bar

See Anti-Roll Bar

Auto display

Radios with this feature automatically display the setting for the trim lever you’re using, so you don’t have to scroll through menus.

Auto start

The exact operation of this feature varies with brand, but in general, it lets you program a throttle position that the radio will automatically transmit as soon as the trigger is moved out of neutral. You might set it for 1/2 throttle as a traction-control device or for full throttle for a drag-style launch—or anywhere in between. Once the trigger has returned to neutral or the brake has been applied, the throttle function returns to fully proportional control.

- B -

Back Marker

Any racer that is being lapped.

Ball Bearing

A ball bearing is a bearing assembly which uses captured balls as the rolling elements. Ball bearings are used in wheels and other rotating parts on RC cars or trucks, allowing the vehicle to roll more freely. This allows the nitro engine or electric Motor to power the RC vehicle to its fastest speeds.

Ball Cup

The small, plastic ‘cup’ shaped piece at the end of adjustable turnbuckles. Ball cups snap on to ball ends to provide a rigid, adjustable link.
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.
Moved around (to different locations in a given area), they aid in adjusting certain tuning options.


A type of wheel used in extreme off-road applications. A locking ring screws down onto the wheel to lock the “bead” of the tire in place. This differs from conventional wheels which use glue to mount the tire.


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, a battery elimination circuit reduces the voltage coming from the main battery to power certain electronics like servos oor the radio equipment, without the need for a separate receiver pack.

Most speed controllers feature built-in BECs to perform this task automatically.

Some power-hungry accessories like high-powered servos and lighting kits may require a separate, more powerful external BEC.


A bellcrank is a lever which transforms force from the steering servo to the front wheels of a RC car. Bellcranks provide precise steering response and maintain the correct geometry for responsive handling.

Used in most RC cars, it 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.


Binding or linking is the process of pairing one 2.4 GHz hand-held transmitter to a corresponding vehicle-mounted receiver. This is what allows the remote control to communicate with the vehicle. Once bound, they will stay paired, even when powered down.

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 bluish tint results from tire wear.

Body Roll

The changing of the chassis’ angle in relation to the ground when going through turns or corners. Body Roll is prevented using and Anti-Roll Bar.

Body Reamer

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


This is the diameter of the cylinder hole in the nitro engine block for the pistons.

Bottom End

The acceleration rate of a RC car from a dead stop.


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 small piece of conductive metal that makes contact with the commutator inside an electric motor.

Brushed (motor)

Brushed motors use fine copper “brushes” to transfer electricity to the central armature of the motor. When electricity is applied, it creates a magnetic force which spins the central shaft in the motor. Brushed motors are inexpensive and simple in their design, but the brushes will wear out over time.

Brushless (motor)

A brushless motor features a powerful magnet on its central shaft which is driven by a magnetic force created in the surrounding can. 


A fundamental structural part of any RC car. Typically, the bulkhead hosts a differential and several major components rely on the bulkhead to join them to the chassis: shock towers, upper chassis plates and suspension arms.

Bump steer

The changing of steering angles while the suspension is moved throughout its range of travel. Bump steer causes a vehicle to turn itself when one wheel hits a bump or falls down into a hole or rut. Excessive bump steer increases tire wear and makes the vehicle more difficult to handle on rough roads.


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 lubrica

- C -


This refers to the angle of the tires in relation to the ground, as seen from the front and rear of the RC car.

Zero camber (90 degrees) refers to tires that are exactly perpendicular to the ground.

Negative camber is when the top of the wheel is leaning towards the center of the vehicle.  Negative camber is commonly used to add stability in bumps. 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.

Positive camber is when the top of the wheel is leaning away from the center of the vehicle. Positive camber is not commonly used and should be avoided

Camber is adjustable via the turnbuckles. This allows suspension tuning for better handling in different conditions


A small electronic component used as a filter to reduce radio noise generated by an electric motor.

Carbon Fiber

An extremely strong thin fiber made by pyrolyzing synthetic fibers, such as rayon, until charred. Carbon fiber is used, in RC, to make strong, lightweight parts such as chassis, shock towers, top decks, etc.


Found on RC nitro cars, also referred to as a carb, the carburetor is a device that combines nitro fuel with air to create a combustible mixture in 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  RC kits and is fine for most applications. The slide carb provides a quicker response and is therefore more desirable to the more serious enthusiast.

The carburetor is adjustable and will require periodic tuning to keep the engine running in peak form.


The angular displacement of the steering axis from the vertical axis of the steered wheel, as seen from the side of the RC car. The steering axis in a car with dual ball joint suspension is an imaginary line that runs through the center of the upper ball joint to the center of the lower ball joint, or through the center of the kingpin for RC cars having a kingpin.

Caster angle of steering wheel seen from the side of the vehicle - RC Glossary - RCTracks.io

Caster causes a wheel to align with the direction of travel, and can be accomplished either by caster displacement or caster angle(the main pivot in the steering mechanism) in relation to the ground. 

Caster can have a great effect on how a RC car enters and exits turns and corners. Increasing caster (positive), so that the kingpin is angled back, will generally increase steering going into a corner and a slight decrease in steering coming out. 

Negative caster will decrease the amount of steering going into a corner, but will increase the amount of steering in the middle and while exiting that corner. 


Center of Gravity

The point on the chassis at which the vehicle balances with all components installed. Ideally, a vehicle’s center of gravity should be as low as possible.

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 RC car.


The main frame of a vehicle to which all the other components attach. Made from aluminum, plastic composites or carbon fiber, this is the main platform to which all other components attach.

Clutch Bell

The clutch bell houses the clutch shoes of an RC nitro engine which, under predetermined RPM’s, expand and come in contact with the clutch bell. The friction causes the clutch bell to spin which, in turn, rotates the spur gear and sends the RC car in motion.

The clutch bell performs the same function as a pinion gear on an electric motor. Changing the number of teeth on a clutch bell alters the way a RC car performs. Fewer teeth produce more low-end torque, whereas more teeth increase top-end speed.

Clutch Shoes

Clutch shoes are attached to the engine flywheel and expand under increasing RPM to engage the clutch bell. The clutch bell spinning makes the spur gear turn, and the RC car moves forward!

Cold Solder Joint

A solder joint with poor electrical integrity. It is not mechanically, or electrically solid, and has a rough or grainy look. Cold joints can cause radio interference.

Comm Lathe

An electric motor’s commutator will wear over time. This lathe is used to cut thin layers of material until the surface is like new.

Compound (Tire)

The type of rubber that a tire is made of. A softer compound will usually have more traction than a harder compound, but will often wear quicker.


The pressure that builds in a glow engine as the piston moves through the up-stroke.

Connecting Rod

The rod that connects the piston to the crankshaft in a glow engine.

Contact Patch

The “footprint” of a tire; the part of a tire which comes in contact with the road surface.

Crank Shaft

In a glow engine, 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.


A small interchangeable element in radio systems that determines what frequency that radio will operate on. You will find a crystal in the transmitter and in the receiver.

Current Limiter

An adjustment on an ESC to limit the current that the motor can draw during acceleration. This eliminates high, inefficient current spikes and reduces wheel spin.

CVD / Constant Velocity Drive

Similar to a dogbone, CVD is 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.

- D -

Damping (not Dampening)

The resistance caused by fluid in a shock body when the shock piston moves through it. Heavier oil, more damping.

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.


To prevent the trigger from being too “touchy,” all transmitters are designed to have a small area of trigger travel that will not transmit a forward or reverse command. This is known as “deadband.”

Differential (Diff)

A differential transfers power from the central driveshaft to the drive wheels and allows them to spin at different speeds. The RC differential, or “diff,” enables the outside wheel of a vehicle to spin faster and travel farther than the inside wheel during a turn. 

The RC differentials are often filled with thick silicone fluid which controls how much the wheels can spin independently of each other.

Differential (Diff) Balls

In a ball differential, the balls float within the diff gear and cause the opposite side to rotate in the opposite direction when the diff gear is held and one outdrive is turned.

Differential (Diff) Rings

The metal rings that the diff balls run against.


The process of draining a battery of its stored energy, either by running a vehicle or connecting the battery pack to discharge device.


Many battery chargers include a built-in discharging function. A better way to discharge your packs, however, is with a separate discharger that connects directly to the battery pack. One common style looks like a row of small light bulbs.

Direct servo control

A patch cord that is attached to the RC transmitter (TX) and the RC receiver (RX) allows you to adjust the servos or ESC (on an RC electric car) without your having to turn on the radio and emitting a signal that can cause interference with others on the same channel.

Display-only mode

This allows you to turn on the LCD screen without sending a radio frequency (RF) signal. This is very useful for making radio adjustments in the pits when other racers share the same channel.


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. Because of the roll pins found at each end, the finished product resembles a dogs bone.


The effect of air contacting the car body’s sloped surfaces. Downforce is created by the air dam, hood, windshield, roof, spoiler(s) and wing(s) of the car. More downforce increases drag and slows the car, but raises the tire temperature, making the car easier to drive. Less downforce raises the top speed by reducing drag. The car should be set up so that it can drive with minimal downforce.


Draft is the area directly behind a car where the air is disturbed and there is very little wind. Vehicles in a draft will be faster than the car creating the draft because the car in the draft does not have to use power to move the wind…it is merely using the power to propel the vehicle.


Resistance encountered that impedes motion or movement.

Drag Link

A bellcrank steering systems consists of 2 posts connected by a bar, the ‘link’. This bar is the drag link and allows the steering force applied to one wheel to be applied to the other. 

It is also referred to, by some, as Ackerman link.


A shaft that transfers rotational force from one component to another. Driveshafts are often formed from two telescoping halves to allow changes in length due to suspension compression.


Droop is the amount of down travel the tires have when lifting up on the chassis.

Droop schema by SoDialed.com - Caster angle of steering wheel seen from the side of the vehicle - SoDialed Illustration - RC Glossary - RCTracks.ioRCTracks.io

Dual Rate

An adjustment found on most transmitters which allows adjustment of the distance a servo arm will travel. This is a useful function for many beginners, who tend to over-control their vehicles.

This allows you to alter the servo travel on both sides of neutral simultaneously, and it’s most often used for the steering channel. Unlike endpoint adjustments, which are made independently for left and right throw, dual-rate adjustments affect servo throw in both directions.

- E -

Electronic Speed Control (ESC)

The ESC is the “brain” of the RC electric car. The ESC controls how much power flows from the battery to the motor to generate speed. It also sends power to the receiver to power servos, fans, and other accessories. The ESC is programmable with many safety and convenience features like Low-Voltage Detection and various drive modes. 

Electronic speed controls replace the mechanical speed control and servo, providing enhanced power efficiency and precision in an electric RC car, truck or boat. In addition, they are lighter which improves the performance of most electric models. Also known as an ESC.


Endpoint adjustments allow you to set left and right servo throw independently,   adjusting the length of servo travel in one direction. Adjustable endpoints are particularly useful for adjusting a RC nitro car’s throttle/brake servo because it may require significantly more travel to operate the throttle than the brake.  Also known as EPA.

Exponential Rate

This allows you to adjust the servo’s response around neutral. It 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%.

This allows you to adjust the servo’s response around neutral. For example, if the expo is set for a negative value, the servo will respond less quickly to steering wheel or trigger movement near neutral. Conversely, it will respond more quickly as the limits of travel are reached. A positive expo setting does the opposite: it’s faster near neutral and slower as the servo reaches its travel limit. The greater the expo value, the greater the difference in servo speed, from slowest to fastest.

- F -


This feature is only found on PCM radio systems. The fail-safe system returns the throttle servo or ESC and steering servo to neutral positions in the event of radio interference or loss of power to the model. This invaluable feature prevents your RC car from going out of control if you encounter a glitch.

Final Drive Ratio

The transmission ratio determined by combining the internal drive ratio to the pinion/spur combination using this formula: Spur Gear divided by Pinion Gear multiplied by the Internal Drive Ratio. Also known as Final Drive or FDR.

Fixed Link

Camber and steering links on many RTR (ready to run) RC 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.


A measure of how much a certain part will bend under varying degrees of pressure or force. Every part will bend or flex, some more than others.


Actually rosin, but often referred to as “flux”; helps the flow of solder.


The flywheel is the larger metal wheel that sits behind the clutch bell and aids the engine’s crankshaft with momentum and idlingFor more torque and smoother idle use a heavier flywheel; for improved top speed and throttle response use a lighter flywheel. Also used to start a RC nitro vehicle not equipped with a pull-start.

Foam Inserts

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

Frame rate

Frame rate is the speed at which the transmitter “fires” bundles of information to the receiver. Most pro-level radio systems allow a faster than usual frame rate to better exploit the superior processing speeds of digital servos.

Frequency modulation (FM)

Provides cleaner, more reliable reception than amplitude modulation (AM) systems and is preferred by racers because FM systems are less prone to glitching at the track. Also referred to as “PPM.”

Fuel Gun

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

- G -


A standard of measure used to determine the thickness of wire.


A general term that normally refers to either the spur gear and pinion gear.


Refers to the ratio of the spur gear and pinion gear when compared to the internal final drive ratio of your RC car.

Gear Mesh

The alignment of the teeth on the spur gear to the corresponding teeth on the pinion gear. If the teeth are meshed too tightly, premature wear and excess heat may result. If they are meshed too loosely, excess noise and stripped gear teeth may result. Consult your owner’s manual for tips on adjusting your vehicle’s gear mesh. 

Gear Ratio

A way of measuring the mechanical advantage of gears acting upon each other. To calculate the gear ratio, divide the number of teeth on the spur gear by the number of teeth on the pinion gear. The higher the numerical value, the greater the mechanical advantage (torque), but the lower the speed. A lower numerical value will generate more speed, but forces the motor to work harder. 

Glow Plug

A glow plug screws into the top of a cylinder head in a RC nitro-powered engine. It is used to ignite the air/fuel mixture and begin the combustion process. 

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 “explosions” in the engine’s cylinder.

Glow Plug Igniter

A powered device (usually 1.2V) which connects to a glow plug. Used to heat the filament in the glow plug in order to start the engine.


This is the fast way around the track. Also known as “the racing line”.

Ground Clearance

The distance between the ground and the lowest part of the chassis. A high ground clearance is advantageous for rock crawling and all-terrain driving.

- H -


A sharp, 180 degree turn on a track; when viewed from above, it resembles a hairpin.


Articles made of metal used to assemble a RC car, e.g., screws, nuts, washers, etc.


A bent piece of aluminum tubing (aluminum exhaust coupling) used on RC nitro cars that transfers exhaust gases from the engine case to the tuned pipe or muffler.

Heat Sink

Made of a heat conductive material (typically aluminum), a heat sink is used to dissipate heat over an increased surface area.

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.


A term used to describe the initial lead at the start of a race.


When the rear end of the RC car has a tendency to kick out when turning with the throttle on. Also known as oversteer.

Horizontal Load

When cornering, it is the force applied to an individual tire in the direction parallel with the road surface.

Hub Carrier

These are the parts of the suspension that hold the bearings and axles. Also called uprights.


A fluid slipper clutch, manufactured by Team Losi, that increases rear traction.

Hydraulic Lock

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

- I -

Idle up

This is used exclusively for RC nitro cars. When idle up is selected, the throttle servo moves to a position you set to speed up the idle for easier starting or warmup. When idle up is switched off, the throttle servo returns to the designated neutral position.

Internal Drive Ratio

A measure of the teeth of a car’s gears and pulleys.

- K -

Kick Up

The angle of the entire front suspension, from horizontal, in relationship to the rest of the chassis.


The hinge pin on which the steering knuckles rotate.

- L -


(Being Lapped) A term used when the lead cars are passing backmarkers, putting them one (or more) laps down.


Light Emitting Diodes are found almost everywhere. LEDs are renowned for their long life and low energy consumption.


Abbreviation for lithium polymer. Rechargeable LiPo battery packs are known for their special chemistry, which allows extremely high energy density and current handling in a compact size. These high-performance batteries require special care and handling and are recommended for advanced users only.


A term used to describe the way an engine is running when the needles on the carburetor are set such that the engine is not getting enough fuel. Running too lean may help fuel economy and appear to make the vehicle run better. However this will cause the engine to run hot and, if not corrected, can cause engine damage.


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.

Linkage (throttle, brake)

Heavy gauge wire is used to connect servo horns to throttle and break controls.


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.

- M -

MHz = Megahertz

Unit of radio frequency. Surface frequencies are 75 MHz and air frequencies of 72 MHz, 27 MHz, and 50 MHz can be used for either ground or air applications. However, a FCC license is required to operate on the 50 MHz (am radio) band.

mAh (Milliamp Hour)

A measure of a battery’s total capacity. The higher the number (ex. 2400 mAh, 3400 mAh) the more charge a battery can hold and usually, the longer a battery will last under a certain load. Typical rechargeable receiver battery packs are in the 800-1400 mAh range. Typical RC car batteries are in the 4200 – 5800 mAh range.

Main Event

The final race after qualifying. Also known as the Main.


This feature allows you to “mix” the transmitter’s channels so that the throttle will also influence steering or vice versa. This function is rarely used with RC cars, but it is popular with RC boats; a little rudder is often mixed with the throttle to prevent the boat from pulling to one side when it accelerates.

Model memory

Lets you store the data for multiple models and various setups for the same model in the transmitter’s memory. Each mode and setup is assigned a model number. Some radios also have model “naming” capability, so you can call up a model by name.


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 RC nitro cars use some type of muffler, device attached to the exhaust outlet of the engine, to reduce the noise output and provide pressure to the fuel tank which helps low speed performance

Muffler Baffle

A restrictor plate inside the muffler which reduces engine noise. This plate can be removed to increase power, but will increase the engine noise!

- N -

Needle Valve

A RC 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.)

Neutral Position

Referring to servos, this is the position the servo is at when it is idle.

NiCd (or NiCad)

Nickel-Cadmium battery. Rechargeable batteries most commonly used to power RC radio transmitters and receivers. Also used in stick packs in electric RC car.

NiMH (Nickel-Metal Hydride)

An abbreviation for nickel-metal hydride. These are battery cells that do not have “cell memory” with slightly less voltage than nickel-cadmium batteries. For the average enthusiast this means less maintenance.

Unlike LiPo batteries, NiMH batteries may be completely discharged without harming the battery. For this reason, NiMh batteries are a good choice for beginners.


Not to be confused with gasoline, nitro fuel combines nitromethane, alcohol, and lubricating oil for explosive power in nitro engines.  It increases a RC engine’s ability to idle low and improves high speed 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.

Refer to the engine manufacturer’s instructions for best results.  Also known as Nitromethane.


- O -

Off-road Car

RC Off-road buggies and trucks are the most popular land vehicles. These cars sport full-travel suspensions and high ground clearance. Their knobby rubber tires give them the ability to tackle any dirt terrain. These cars are available in nitro or electric, and in many different scales. On a dirt track or at the park, these offroad are great fun.


See Wheel Offset.


Unit and measure of electrical resistance.


The measure of electrical resistance, at full throttle, of an ESC at a given temperature. As the temperature increases, the on-resistance increases. A lower on-resistance will give you more power. A lower on-resistance also means the ESC will run cooler.

On-road Car

On-road RC cars don’t have the beefy suspension that the off-road RC cars have, but they are impressive in their authentic looks and all out speed. Built for racing on smooth, paved surfaces, they are available in nitro or electric, and in many different scales.


A donut-shaped circle of rubber or silicone that seals rotating or sliding shafts, used in areas like shock absorbers and differentials.


The outdrive refers to shafts that exit the differential on either side and transfer power out of the transmission to the drive wheels using an axle shaft or universal.


The condition where a final gear ratio is too low for the motor. This results in excessive motor heat and causes the motor to draw more amps from the ESC.


A situation in which the front tires have more traction than the rear tires. This causes the rear tires to lose traction in corners 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

- P -

Peak Charger

When the battery has peaked, meaning it will no longer accept a charge, considerably decreasing the chance of damage to the pack. This means longer run times for your RC car. 


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 cars use a pinion gear mounted onto the motor’s shaft to turn the spur gear. Many different sizes of pinion and spur gears are available to maximize the motor’s power for speed or torque


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.


Pitch refers to the size and spacing of the teeth on a gear. In metric terms, this is called “module.” The gear pitch number represents how many teeth per inch. For instance, a 32-pitch gear with 64 teeth would be 2 inches in diameter. You must always combine two gears of the same pitch.

Planetary Gear Differential

A type of differential that has small gears rotating around the center drive gear.

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 mechanism that allows the starting of a RC nitro car engine without the need for a separate engine starter box. It is attached to the back of the nitro engine.


RC racers’ term used to describe the amount of acceleration a car or truck possesses.

Push / Understeer

If your RC car’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.

- R -

Race Director

The person running and organizing the race. Responsible for calling the drivers to the stand, making sure each car is in the correct spot on the starting grid, calling traffic if necessary, etc.

Racing Line

This is the fast way around the track. Also known as the groove.

RTR (Ready to Run)

Some RC cars are available pre-built and will be indicated by the term RTR (Ready-To-Run). The RTR RC vehicles cost a little more but typically come with everything you need (except a battery and charger). 


An angled tool with a rough surface used to enlarge holes…to mount a body to the chassis for example.

Receiver (Rx)

An electronic device that receives the signal from the hand-held transmitter. The servo and ESC plug into this electronic unit in an RC vehicle. Receivers translate inputs from the transmitter into real-time reactions in the vehicle like steering and throttle control.


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 accidents.


When the needles on the carburetor are set such that the engine is getting too much fuel compared to the amount of air, 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).

Ride Height

The point at which the RC car naturally rides when fully loaded with the necessary equipment.

Rocker Arm

Pioneered on the Revo’s suspension, rocker arms transform the vertical movement of the suspension into horizontal shock movement. This provides longer suspension travel with a lower body profile and allows the shocks to lay flat for a lower center of gravity.


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

Run Time

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

- S -

Sand Bagger

Term used for a good racer running in to low of a main or class, usually resulting because they are to chicken to run with people of their same ability level (ie, sportsman racer running in the novice class).

Self Tapping

A screw that creates threads in the material it is penetrating.


All transmitters have this invaluable feature so you can reverse the servo’s operation by simply touching a button.


A small electronic device that incorporates an electric motor and gearing to provide turning motion. This is the unit that actually does the physical work inside your RC vehicle. 

A servo contains a small motor that, when activated by commands from the transmitter, moves the control linkages for steering, throttle and brakes (on RC nitro-powered cars). Some vehicles with 3-channel radios have a third servo to activate other functions, such as reverse or shifting of gears.

Servo Horn

Attaches to the servo and is the link between the servo and the steering linkage.

Servo Saver

A servo saver is a spring loaded device that fits between a servo and the steering mechanism. A servo saver will twist to absorb sudden shock or impact coming from the servo linkage that might otherwise damage the gears in the servo.

Servo speed

You can’t increase a servo’s speed with this function, but you can slow its transit time. If your new super-servo makes your car feel twitchy, or having a lightning-quick servo is a liability, e.g., in RC oval racing, try adjusting servo speed.

Servo Reversing

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.

When your installation is complete, turn on your transmitter and check each channel. If a channel operates opposite of its intended direction, a simple flick of a switch corrects the problem.


A shock absorber attaches to the suspension arms on a RC car to control their up and down movement for a smoother ride. Shocks are filled with silicone oil to slow the compression and rebound speed of the suspension for better control on rough surfaces. Shock oil is easily changed and comes in many different weights to allow for more precise adjustments.

Shock Oil

The silicon-based oil in a shock. Measured by viscosity, the lower the number, the lighter the damping.

Shock Piston

The small plastic (or nylon) disc that travels up and down inside an oil-filled shock body. It uses holes of different sizes to regulate the rate at which the shock compresses and rebounds.

Shock Tower

A reinforced piece, attached to the chassis, that allows the shocks to be mounted. Shock towers usually have multiple mounting locations (for tuning), and can come in plastic, carbon fiber, or metal (typically aluminum). It often double as mounting points for the body shell.


The side of the tire that extends from the wheel up to the top of the carcass.

Skid Plate

A plastic or metal (usually aluminum or titanium) plate that protects the underside of off road vehicles. Skid plates are considered sacrificial parts and may require replacement if they become damaged. Typically used in RC off-road cars.


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

Slipper Clutch

Found primarily in RC off-road cars, a slipper clutch sits between the motor and the transmission to absorb driveline shocks for improved longevity. It 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 (slippery surfaces). The clutch includes two metal discs separated by adjustable spring-loaded pads which control the amount of slippage


Excessive free movement in a control system. Often caused by a worn out ballcups. This unwanted condition allows the control surface to move without transmitter input


Often referred to as a wing, a spoiler disturbs the air flowing over the body to create downforce on the RC car.

Sportsman Class

Drivers that have won some races and are pretty quick around the track are considered Sportsman. Sportsman drivers typically do not (or should not) have any sponsorship help (if they do, they should be in the Expert/Pro class).

Spring Rate

The stiffness of the springs. Generally, softer springs add traction, harder springs lessen traction. Springs are ‘rated’ by a number value.

Spur Gear

The large gear that meshes with a pinion gear or clutch bell to provide power to a RC car’s drivetrain. It is attached to the differential or transmission.


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

Steering Block

Steering blocks hold the front wheels and provide a rigid mounting point for the steering linkage to turn them. These are commonly constructed of composite material with high-strength aluminum available as an option.

Steering Knuckle

The part of the RC car’s front that steers the wheels. The steering turnbuckles connect the bellcrank and steering knuckles.


How far the shock absorber can compress. It can be limited externally by a clips or a threaded nut on the outside of the shock body.


A very fine trim function—if one “click” of the trim is too much, the subtrim allows you to make a more precise, smaller adjustment.

Suspension Arm

See A-Arm.

Sway Bar

A heavy wire that attaches across either or both the front and rear of a RC car’s suspension arms. It provides tension to keep one wheel on a RC car from compressing higher than the opposite wheel 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 both wheels in contact with the ground for better traction during hard cornering and helps prevent the vehicle from rolling over..

See Anti-Roll Bar.

Synthesized Receiver

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

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Refers to the trigger on pistol-grip style transmitters, or the right stick on dual-stick transmitters.


The rod assembly used to connect the steering bellcranks to the steering knuckles. Also used for camber adjustments. Also known as a turnbuckle.


All RC cars run on some sort of tire. Tires come in different tread designs (for different surfaces) and different compounds (from hard to soft, again, for different surfaces). Purchased tires also include foam inserts. These help support the tire under loads.

Tire Truer

RC 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 is the angle of the wheels in relation to the center line of the RC car. If the wheels point straight ahead, parallel to the center line of the RC vehicle, the toe would be 0°. If the front of the wheels point inward, they would be “toed in.” A slight toe-in of 1°- 2° may aid in straight line stability 

Toe applies to the rear wheels as well. This provides some degree of stability. Too much toe angle will slow you down.


A condition when the front edge of both tires are closer together than the rear edge of both tires. Toe-in will make a car more stable under acceleration but decrease turn-in steering.


A condition when the front edge of both tires are farther apart than the rear edge of both tires. Toe-out increases turn-in steering, yet reduces stability under acceleration and through bumpy sections.

Top Dead Center

In RC nitro engines, the highest point of a piston’s stroke is called top dead center. As the piston moves higher inside the tapered sleeve of the cylinder, it becomes tighter and requires more force to move. On new engines the fit may be so tight that the piston becomes stuck at top dead center. If this happens, you may need to manually free the piston before using the electric starter again

Touring Car

A specific RC on-road car class. Touring Cars are fast and precise and can hit extremely high speeds in short distances. They are available in either nitro or electric powertrains.

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 RC 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.


When you adjust the neutral point of the steering or throttle servo positions, you are adjusting its “trim” or “trimming” the servo.

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 speed while others said off-the-line power.

Turn Marshal

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.


Turnbuckles connect a vehicle’s chassis to the suspension to control the angle and movement of the wheels. 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.

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A situation in which the rear tires have more traction than the front tires. This causes the vehicle to have inadequate steering.

Universal Dogbone

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


At some points on a race track, the inside wheels can lift up because of high cornering forces. This causes a normal ball differential or gear diff to transfer all the available power to the wheel that is in the air. This is because the differential will put any power at the wheel that is the easiest to turn.

User-assigned controls

The digital trim levers or buttons of some computer radios may be assigned different functions to suit your needs; for instance, the knob assigned at the factory to dual-rate adjustment may be reassigned to operate the brake trim.

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The distance between the centerline of the front and rear wheels on a vehicle. Wheelbase can be an important factor in determining which bodies will fit a vehicle.

Wheel Tension

A mechanical adjustment of the force required to operate the steering wheel

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