Arrma Granite Gearing Guide — FDR, Pinion & Spur Chart

Arrma Granite 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 Granite 4X4 3S BLX (Monster 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 1/10 basher monster truck platform with a 2.92 internal transmission ratio, even a single-tooth pinion change shifts your final drive ratio by 3-5%.

The Arrma Granite 4X4 3S BLX is the entry point into the Arrma basher lineup — a 1/10 scale monster truck with a taller internal ratio than most racing platforms because it runs 2.8-inch dBoots Copperhead tires. Its mod-0.8 metric gearing means pinion changes have a larger per-tooth effect than 48-pitch systems.

Basher & Monster Truck Durability Notes for the Arrma Granite

Heavy landing impacts on a platform like the Arrma Granite 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 Granite 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 Granite, this trade-off is amplified by the fixed 2.92 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 50T 48-pitch spur. FDR is calculated as (spur ÷ pinion) × 2.92 internal ratio.

Pinion	Spur	FDR	Typical Use
11T	50T	13.27	High-bite carpet / tight indoor
13T	50T	11.23	High-bite carpet / tight indoor
15T	50T	9.73	Tight outdoor clay / technical
17T	50T	8.59	Balanced club racing
19T	50T	7.68	Open outdoor / high-speed

Understanding Pinion & Spur Gears

Stock Granite uses a 15T mod-0.8 pinion / 50T spur. Bashers converting to 4S packs should drop to a 13T pinion to protect the BLX 100 ESC from over-current shutdowns.

Rollout Targets

Rollout on the Granite lands around 2.9 to 3.2 inches per motor revolution. Because dBoots tires balloon aggressively at 3S voltages, actual on-track rollout is often 10% higher than the bench number.

Motor Temperature Management

The Granite's smaller BLX motor runs hotter than the 6S trucks; target under 170F (77C) after a pack. If you hit 190F, drop a pinion tooth before your next run.

⚠️ 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 Granite 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 Granite

The link below opens the calculator with Custom / Other Chassis pre-selected, the Arrma Granite's internal ratio of 2.92 and its recommended battery of 3S LiPo (11.1V) 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 2.92 ratio + 3S LiPo (11.1V) preset →

Arrma Granite 4X4 3S BLX (Monster Truck) Gearing Guide