Arrma Outcast Gearing Guide — FDR, Pinion & Spur Chart

Arrma Outcast RC Gearing & Optimization Guide

Optimizing your gear ratio is one of the most effective ways to balance speed, torque, and electronics longevity in your Arrma Outcast 6S / 8S BLX (Stunt Truck). The relationship between your pinion gear (attached to the motor) and your spur gear (attached to the transmission) dictates how hard your motor has to work — and on a 1/8 basher stunt truck platform with a 2.6 internal transmission ratio, even a single-tooth pinion change shifts your final drive ratio by 3-5%.

The Arrma Outcast is a stunt-truck variant of the Kraton platform designed for wheelies, backflips, and freestyle bashing. Its taller stance and lighter body shell change how gearing translates to real-world runtime — because the truck spends significant time on two wheels, sustained motor load is lower than a Kraton but instantaneous current spikes on landings are higher.

Basher & Monster Truck Durability Notes for the Arrma Outcast

Heavy landing impacts on a platform like the Arrma Outcast routinely bend motor mounts out of parallel with the spur, which is the single fastest way to strip a 48-pitch spur gear mid-session. After every big air session, sight down the pinion-to-spur mesh and confirm the motor plate has not shifted — a mount that has moved even half a millimeter will chew teeth within a pack. Just as importantly, check your center differential fluid thickness on a regular schedule; on high-power basher drivetrains the center diff is what manages extreme power distribution between the front and rear axles, and thin or contaminated fluid lets the light end spin up under throttle punch, spiking motor amp draw and cooking spur teeth from the inside out.

🛠️ Essential Tools Required for Gearing Changes

Hex drivers (1.5mm, 2.0mm, or 2.5mm depending on the Arrma Outcast variant)
Paper strip (for setting precise gear mesh)
Infrared temperature gun (crucial for monitoring motor heat after each run)
Threadlock (for the pinion gear grub screw)
Pinion gear puller (recommended when swapping gears on a hot motor shaft)

📋 Comprehensive Gearing & Temperature Guide

1. Understanding Pinion vs. Spur Gear Adjustment

Changing your gears alters your final drive ratio. Installing a larger pinion gear or a smaller spur gear increases top-end speed but increases the load on the motor, causing it to run hotter. Conversely, a smaller pinion or larger spur increases torque and acceleration while lowering top speeds and keeping your motor cool. On the Arrma Outcast, this trade-off is amplified by the fixed 2.6 internal ratio — small external changes have a direct thermal consequence.

2. How to Set a Perfect Gear Mesh

Improper gear mesh will quickly strip your spur gear or bind your drivetrain.

Loosen the motor mount screws slightly.
Place a small strip of standard notebook paper between the pinion and spur gear teeth.
Press the gears tightly together and tighten the motor mount screws.
Roll the paper out. The paper should have clean, crisp crinkles without ripping.

Recommended Pinion & Spur Chart

All combinations use a 46T 48-pitch spur. FDR is calculated as (spur ÷ pinion) × 2.6 internal ratio.

Pinion	Spur	FDR	Typical Use
12T	46T	9.97	Tight outdoor clay / technical
13T	46T	9.2	Balanced club racing
14T	46T	8.54	Balanced club racing
15T	46T	7.97	Open outdoor / high-speed
16T	46T	7.48	Open outdoor / high-speed
17T	46T	7.04	Open outdoor / high-speed

Understanding Pinion & Spur Gears

Stock 6S Outcast setups use a 16T mod-1 pinion / 46T spur. For stunt-focused driving a 14T pinion trades top speed for cleaner backflip rotation and lower ESC temps during hard landings.

Rollout Targets

Outcast rollout with stock tires lands near 5 inches per motor revolution. Freestyle bashers who prioritize wheelie response typically gear one tooth shorter than the stock Kraton pinion to shift power delivery lower in the RPM band.

Motor Temperature Management

Because Outcast drivers idle at higher throttle percentages during stunts, motor temps trend 10F higher than a Kraton driven at speed. Keep the BLX motor under 180F (82C) and check the ESC fan is clear of dirt after every session.

⚠️ Critical Safety & Temperature Warning

Always use an infrared thermometer to check your motor and ESC temperatures during a run. RC electric brushless motors should never exceed 160°F (71°C). Exceeding 180°F (82°C) risks permanently demagnetizing your motor rotor and frying your Electronic Speed Controller. If your Arrma Outcast is running above these thresholds, you must "gear down" by installing a smaller pinion gear immediately, improve airflow with a larger motor fan, and inspect the drivetrain for binding.

Calculate a custom FDR for your Arrma Outcast

The link below opens the calculator with Custom / Other Chassis pre-selected, the Arrma Outcast's internal ratio of 2.6 and its recommended battery of 6S LiPo (22.2V) already set — just plug in your pinion, spur, motor, and tire to see top speed, runtime, and FDR for your exact setup.

Open calculator with 2.6 ratio + 6S LiPo (22.2V) preset →

Arrma Outcast 6S / 8S BLX (Stunt Truck) Gearing Guide