Axial Capra Gearing Guide — FDR, Pinion & Spur Chart

Axial Capra RC Gearing & Optimization Guide

Optimizing your gear ratio is one of the most effective ways to balance speed, torque, and electronics longevity in your Axial Capra 1.9 UTB (Precision Rock Crawler). 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 precision rock crawler & ultra trail buggy platform with a 44.2 internal transmission ratio, even a single-tooth pinion change shifts your final drive ratio by 3-5%.

The Axial Capra 1.9 UTB is a purpose-built Ultra Trail Buggy focused on precision rock crawling rather than scale trail cruising. Its portal-free straight axles with high-clearance links and low-slung skid plate produce a very tall effective final drive — roughly 44:1 — which is why the stock 35T brushed motor feels perfectly matched to slow technical lines.

Rock Crawler & Trail Truck Drivetrain Notes for the Axial Capra

Ultra-low speed crawling on a Axial Capra demands heavy grease packed into the portal or straight axles to damp shock loading and keep the ring-and-pinion quiet under sustained torque. Whether you are running a precisely tuned slipper clutch or a fully locked differential, the goal is to make the drivetrain deliver torque smoothly instead of shock-loading it into a rock face. High-torque binds against a ledge can spike amp draw well past continuous ratings and overheat the motor even at walking pace, so a small in-line wattmeter or an ESC with current logging is worth more than another temperature reading — heat shows up long after the damage is already done.

🛠️ Essential Tools Required for Gearing Changes

Hex drivers (1.5mm, 2.0mm, or 2.5mm depending on the Axial Capra 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 Axial Capra, this trade-off is amplified by the fixed 44.2 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 56T 48-pitch spur. FDR is calculated as (spur ÷ pinion) × 44.2 internal ratio.

Pinion	Spur	FDR	Typical Use
11T	56T	225.02	High-bite carpet / tight indoor
13T	56T	190.4	High-bite carpet / tight indoor
15T	56T	165.01	High-bite carpet / tight indoor
17T	56T	145.6	High-bite carpet / tight indoor
19T	56T	130.27	High-bite carpet / tight indoor

Understanding Pinion & Spur Gears

Stock Capra uses a 15T 32-pitch pinion / 56T spur. Crawlers competing at UTB events typically drop to a 13T pinion for even finer throttle control on technical lines.

Rollout Targets

Rollout is well under half an inch per motor revolution, which is exactly what makes the Capra able to inch across knife-edge obstacles without a hint of throttle overshoot.

Motor Temperature Management

Ultra-slow crawling generates most of its heat as stall current at obstacles. If the motor is more than warm to the touch, an inline wattmeter is worth more than another temperature reading.

⚠️ 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 Axial Capra 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 Axial Capra

The link below opens the calculator with Custom / Other Chassis pre-selected, the Axial Capra's internal ratio of 44.2 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 44.2 ratio + 3S LiPo (11.1V) preset →

Axial Capra 1.9 UTB (Precision Rock Crawler) Gearing Guide