RC Servo Torque & Speed: What the Numbers Mean
Every servo listing throws torque and speed at you—picking the wrong balance leads to weak or twitchy steering. Here's what the numbers mean.
Every servo listing throws two numbers at you — torque and speed — and picking the wrong balance leads to either a weak, overpowered steering setup or a twitchy one that overheats.
Torque: The Steering Strength
Torque is usually listed in kg·cm (kilogram-centimeters) and tells you how much rotational force the servo can generate — essentially, how strong it is at turning your wheels against resistance.
- Low torque (under ~10 kg·cm): Fine for lightweight on-road cars with minimal steering resistance.
- Mid torque (~10–15 kg·cm): Common for general bashing, short course trucks, and most stock-to-mild upgrades.
- High torque (15+ kg·cm): Needed for crawlers (turning against high-traction tires at a standstill) and larger, heavier vehicles.
If your servo is underpowered for the car, you'll notice sluggish or incomplete steering response, especially at low speed or against resistance (like rock crawling).
Speed: How Fast It Reacts
Speed is measured in seconds per 60° of rotation (lower number = faster).
- Racing / high-speed driving: Faster servos (0.05–0.10 sec/60°) give quicker steering corrections at speed.
- Bashing / general use: Mid-speed servos (0.10–0.15 sec/60°) are usually plenty and often more affordable.
- Crawling: Speed matters less than torque and precision — many crawler-specific servos prioritize fine control over raw speed.
The Trade-off
Faster servos and higher torque both typically mean higher current draw and cost. There's rarely a servo that maxes out both without a significant price jump — match the spec to what your driving style actually needs rather than buying the highest numbers available.
Metal vs Plastic Gears
Separate from torque/speed specs, gear material matters for durability:
- Plastic gears: Lighter, cheaper, fine for lower-torque applications, but more prone to stripping under high load or impacts.
- Metal gears: More durable under high torque or repeated impacts (bashing, crawling), heavier, and typically more expensive.
Quick Matching Guide
| Use Case | Torque Priority | Speed Priority | Gear Type |
|---|---|---|---|
| On-road racing | Medium | High | Metal preferred |
| Bashing | Medium | Medium | Metal for durability |
| Crawling | High | Low-Medium | Metal, high-torque |
| Light on-road | Low-Medium | Medium | Plastic acceptable |
Match the servo to the actual resistance your steering system will face — a crawler and a race car need almost opposite priorities, even though both are "just steering the front wheels."
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