HPI Racing Savage XS Flux Chevrolet El Camino SS

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.

• Monster trucks have tall tires and long suspension travel, built for jumping and rough ground rather than a race track.

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

• The cost is more parts to maintain.

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.

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 360 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.

• On this car one tooth changes the gearing by about 3.6%.
• A bigger pinion loads the motor and ESC harder, so check the maker's gearing chart and feel the motor temperature after a run.

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, differentials and axle gears.

• It is fixed by the design; the gearing you change is the pinion and spur.
• This one is worked out from the tooth counts the maker publishes.

Spur teeth divided by pinion teeth: the part of the gearing that a pinion or spur swap changes.

• Here it is 2.000:1.

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.

• Among 1/10 monster trucks in the catalog, the middle half run between 11.3:1 and 15.1:1 on stock gearing; this one is 9.4:1, taller than most.

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

• This approximate diameter comes from a replacement advertised for the identified OEM tire. Calculated speed and rollout use this working size; measure your fitted tires for a closer comparison.
• At high speed tires can balloon and grow, so the real gearing gets taller as the car goes faster.

How far the car moves for one turn of the motor: tire circumference divided by final drive.

• It lets you compare gearing across different tire sizes; more rollout is taller gearing.
• Here it is 36.3 mm.

The hex on the axle that the wheel locks onto and is driven by. A wheel must match the hex size to fit.

• 12 mm is the common size on 1/10 cars, so most 1/10 wheels fit; offset and width still vary.
• The wheel nut is a separate size, so check its thread too before buying nuts.

Stock tire width: A documented stock wheel, tire, or axle measurement. Stock dimensions alone do not establish the largest size that will clear the body and suspension.

What the shocks are and how they are built, as the maker describes them.

• Oil-filled shocks damp with silicone oil; friction shocks, found on some entry-level cars, damp with a sprung plunger and cannot be tuned with oil.
• Threaded bodies set ride height with a collar you turn, rather than clips.
• The shaft size matters when buying seals, ends and rebuild kits.

RPM per volt with no load on the motor. Higher KV spins faster on the same pack; lower KV on more cells can reach the same RPM with less current.

• Under load the real RPM is lower.

The diameter of the motor's output shaft. A pinion's bore, the hole in its middle, must match it.

The highest LiPo cell count the maker rates the electronics for.

• The maker does not publish it.

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

• The continuous figure is what it can carry all run; the burst figure only for moments, such as a launch.
• A motor or pack that pulls more than this risks the ESC.

The stock servo that steers the car.

• Plastic gears are light and cheap but strip more easily from hard knocks to the front wheels.

How hard the servo can turn, at the voltage the maker rates it.

• More torque steers heavier cars and bigger tires more precisely and holds the wheels straight over rough ground.
• Kilogram-centimetres and ounce-inches measure the same thing; the other unit is converted for comparison.

How long the servo takes to turn 60 degrees, at the voltage the maker rates it.

• A smaller number is a quicker servo, which feels sharper when changing direction.

Stock servo spline: A documented servo or steering interface for this model. Matching torque alone does not establish mounting or horn fit.

• This working size comes from a replacement advertised for the identified OEM part. Confirm the fitted part before ordering; a replacement's size may differ.

Stock servo dimensions: A documented servo or steering interface for this model. Matching torque alone does not establish mounting or horn fit.

• This working size comes from a replacement advertised for the identified OEM part. Confirm the fitted part before ordering; a replacement's size may differ.

Servo mount pattern: A documented servo or steering interface for this model. Matching torque alone does not establish mounting or horn fit.

• This working size comes from a replacement advertised for the identified OEM part. Confirm the fitted part before ordering; a replacement's size may differ.

Theoretical top speed is unavailable because rated battery cell count is 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.

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.