Axial SCX30 Jeep CJ-7 Renegade

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 brushed motor carries current through carbon brushes that rub on the commutator.

• It is cheaper and smooth at low speed.
• The brushes wear and the motor loses power over time.
• That low-speed smoothness is why so many crawlers use one.

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 141 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 9.1%.
• Crawlers run small pinions for slow, precise wheel speed on climbs; a bigger one is quicker on the trail but harder to control on rocks.

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.

The stated length of the complete shock assembly. Sources may use mounting-eye centers or a nominal assembly length.

• Compare fully extended mounting-eye spacing, compressed length and mounting hardware before ordering. A longer shock changes ride height and travel, and can bind at full droop or bottom out.

Front upper shock mount: A documented shock mounting interface at the named end and eye. A ball stud or standoff is distinct from a through-bolt. Match the mounting type, thread and eye dimensions when choosing a replacement shock.

Front lower shock mount: A documented shock mounting interface at the named end and eye. A ball stud or standoff is distinct from a through-bolt. Match the mounting type, thread and eye dimensions when choosing a replacement shock.

Rear upper shock mount: A documented shock mounting interface at the named end and eye. A ball stud or standoff is distinct from a through-bolt. Match the mounting type, thread and eye dimensions when choosing a replacement shock.

Rear lower shock mount: A documented shock mounting interface at the named end and eye. A ball stud or standoff is distinct from a through-bolt. Match the mounting type, thread and eye dimensions when choosing a replacement shock.

Brushed motors are commonly described by can size and turns. No motor KV is published for this vehicle; turns alone cannot supply an exact value.

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

• 2S is 7.4 V nominal and 8.4 V off the charger.
• Running more cells than this risks the ESC and motor.
• Many cars also run on fewer cells, only slower.

The motor fitted at the factory, as the maker names it.

• In a name like 3285, the digits usually give the can size: 32 mm across and 85 mm long. A bigger can makes more torque and sheds heat better.
• Brushed motors are often named by can size, such as 540 or 550, and by turns: fewer turns is faster.

The electronic speed control. It feeds power from the battery to the motor as you work the throttle, and usually powers the receiver and servo too.

• An amp figure in its name is normally the maker's continuous rating.
• A brushed ESC cannot run a brushless motor.
• Crawler ESCs usually have a strong drag brake, which holds the truck still on a slope when you let off the throttle.
• Set its low-voltage cutoff for LiPo, so a pack is not run flat.

The plug on the battery lead. Your battery needs the same plug.

• An adapter works, but it adds resistance and another joint that can work loose.

The published size of the battery compartment or the stated maximum pack dimensions.

• Read the dimension labels beside the value, then compare with the battery's case size rather than its capacity.
• Allow room for the leads and the battery restraint.

Theoretical top speed is unavailable because motor KV and stock tire outside diameter are missing.

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

The vehicle's weight as the maker states it.

• The maker does not say whether it includes a battery.
• On a crawler, where the weight sits matters as much as how much: weight low and in the axles helps it climb.

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.