WLtoys 104006 Pro

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.

• Crawlers are built for slow, controlled climbing over rocks: very low gearing, flexible suspension and locked axles.

All four wheels are driven. That gives more grip under power, especially on loose ground.

• The cost is more parts to maintain.
• A crawler needs every wheel pulling to climb.

A brushless motor has no brushes to wear, so it makes more power and runs more efficiently than a brushed one.

• It needs a brushless ESC.
• Crawler brushless systems are usually sensored, so the motor turns smoothly from a standstill.

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 568 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.

The small gear on the motor shaft. Fewer teeth gear the car shorter: quicker acceleration, lower top speed and a cooler motor. More teeth do the opposite.

• It depends on the motor you fit, so the maker does not list one.

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.

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

• That chain is why a crawler's figure is much higher than other classes'.
• 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.

• Crawlers run far higher ratios than other classes, so the truck can creep and hold on a climb.

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

• Crawler wheels are named by rim size, such as 1.9 or 2.2 inches; that is the wheel, not this tire diameter.

Motor KV is the RPM a motor turns per volt with no load.

• The maker does not publish it.

The highest LiPo cell count the maker rates the electronics for. Each cell is 3.7 V nominal and 4.2 V fully charged.

• 3S is 11.1 V nominal and 12.6 V off the charger.
• Running more cells than this risks the ESC and motor.
• Many cars also run on fewer cells, only slower.

The size of the stock motor's can, as the maker names it.

• In a name like 3544, the digits give the can's diameter and length in millimetres. A bigger can makes more torque and sheds heat better.

The current the stock speed control is rated to carry, as the maker states it.

• It is the continuous figure: what it can carry all run.
• A motor or pack that pulls more than this risks the ESC.

Theoretical top speed is unavailable because motor KV, stock tire outside diameter and complete final drive ratio are missing.

• Enter the missing inputs in the calculator to work out a theoretical speed.

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.

• On a crawler it also decides how well the truck clears a ledge without the chassis catching.