Traction Hobby RAM 1500 BRS Brushless

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.

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 7.1%.
• 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.
• The Gearing parts table below shows this car's pitch and part numbers.

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 nominal size of the hole that mates with the motor shaft.

• Match the pinion mounting method as well as its size. A press-fit hole cannot be inferred from motor shaft diameter.

The tooth spacing of the fitted gear, stated as metric module or diametral pitch.

• The meshing pinion and spur need matching pitch. A missing pitch can be inferred from the other fitted gear; module and diametral pitch are not silently converted.

The tooth spacing of the fitted gear, stated as metric module or diametral pitch.

• The meshing pinion and spur need matching pitch. A missing pitch can be inferred from the other fitted gear; module and diametral pitch are not silently converted.

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 size printed for this link in the exact-model maker parts list.

• The listed length describes the part, not necessarily the distance between the installed rod-end pivots. Measure the assembled link before ordering a different style of replacement.

The size printed for this link in the exact-model maker parts list.

• The listed length describes the part, not necessarily the distance between the installed rod-end pivots. Measure the assembled link before ordering a different style of replacement.

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.

• On 4S (14.8 V nominal) this motor spins about 26,640 rpm with no load.
• Under load the real RPM is lower.

A nominal motor-shaft fit inferred from the identified fitted pinion.

• This is an inferred mating size, not a measured shaft diameter. Check for adapters and confirm the mounting method before ordering.

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

• 4S is 14.8 V nominal and 16.8 V off the charger.
• Running more cells than this risks the ESC and motor.
• Many cars also run on fewer cells, only slower.

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.
• XT plugs are sold on packs from many makers.

The stock servo that steers the car.

• A digital servo holds its position more firmly and reacts sooner.

Theoretical top speed is unavailable because complete final drive ratio is missing.

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