Primal RC Dodge Challenger Gas RTR

The kind of vehicle the maker sells it as. It sets what the car is built to do and which cars it is fair to compare it with.

• Street covers on-road bashers: speed-run, muscle and drag cars built for straight-line speed rather than racing.

Only one axle is driven, the rear on almost every 2WD RC car.

• It is lighter and simpler, and it takes more throttle control on loose ground.

A two-stroke engine running gasoline mixed with oil, used on the largest cars.

• It has no motor KV or battery rating.

Ready to run: built at the factory with the electronics installed.

• Some come without a battery or charger; the maker's box contents say which.

The maker's nominal size compared with a full-size vehicle. It works more as a class label than a measurement.

• A 1/10 monster truck is far bigger than a 1/10 touring car, so compare length and weight for real size.
• This one is 1,003 mm long.

The maker's product number for this exact version.

• A V2, a new color, or a kit instead of an RTR usually has a different number, and parts can differ between them.
• Check it against your box or receipt before ordering parts.

On a nitro car the gear on the engine is the clutch bell.

• Its teeth work like a pinion's: more teeth gear the car taller, for more top speed and slower acceleration.

The large gear the pinion drives. A bigger spur with the same pinion gears the car shorter.

• Pinion and spur must have the same pitch, or tooth size, to mesh.
• On a nitro car the clutch bell drives it.

Every reduction after the spur, multiplied together: transmission, differentials and axle gears.

• It is fixed by the design; the gearing you change is the pinion and spur.

How many times the motor turns for one turn of the wheels. A higher number is shorter gearing: more acceleration and pulling power, less top speed.

The outside diameter of the mounted tire, tread to tread. A taller tire covers more ground each turn, which gears the car taller.

• At high speed tires can balloon and grow, so the real gearing gets taller as the car goes faster.

An engine has no KV rating.

• Nitro engines are sized by displacement in cubic inches, such as .21.

An engine car has no drive battery.

• A small receiver pack or a BEC powers the radio and servos.

An engine has no KV, so a theoretical top speed cannot be worked out from the gearing alone.

Overall length as the maker states it, usually with the body fitted.

• Useful for comparing real size, since scale labels are loose.

Overall width as the maker states it, usually with the body fitted.

• A wider car is more stable in corners and harder to roll over.

Overall height as the maker states it, usually with the body fitted.

• Useful when checking it fits a shelf, a bag or a car trunk.

The distance between the front and rear axle centers. A longer wheelbase is steadier at speed and over bumps; a shorter one turns more tightly.