Choosing a servo for your RC car: what should you look for?

The servo is the component that converts your steering commands into wheel movement. On many ready-to-run (RTR) RC cars, the stock servo is just strong enough to drive, but not to turn the wheels properly under load, in tall grass, or among rocks. A better servo is therefore one of the most popular upgrades. But which one should you choose? Let’s go over the key specifications.

Torque (force)

Torque is the force a servo can deliver, usually expressed in kg·cm. A servo rated at 25 kg·cm can lift a 25 kg weight 1 cm from the shaft. The heavier your car, the larger the tires, and the more grip you have, the more torque you need.

Guidelines:

Speed

Speed is expressed in seconds per 60° of rotation, for example 0.10 s/60°. The lower the number, the faster the servo responds. Speed is important for racers because every fraction of a second counts through a turn. Speed matters less for crawlers: torque always wins there.

Voltage: standard or HV

Servos are rated for a specific voltage, such as 6.0 V or 7.4 V. HV servos (High Voltage) can operate at 7.4 V or 8.4 V, delivering more torque and speed. Keep in mind: the torque listed on the packaging is usually for the highest voltage.

Your servo gets its power from the BEC in your ESC. Many standard ESCs only supply 6 V and limited current. A powerful servo may draw more current than the BEC can provide, causing your receiver to shut down ("brown out"). For high-torque servos, an external BEC is often a smart investment.

Digital or analog

Almost all modern servos are digital. They hold their position more firmly, respond more precisely, and have more torque in the mid-range. Analog servos are cheaper, but are mostly found in entry-level models these days.

Gears: plastic, metal, or titanium

• Plastic – light and inexpensive, but breaks easily on impact.
• Metal (steel or aluminum) – the standard for bashers and crawlers. Much stronger.
• Titanium – very strong and light, found mainly in top-end servos.

We recommend metal gears for any car that jumps, crashes, or crawls.

Motor: cored, coreless, or brushless

Cheaper servos use a conventional cored motor. Coreless motors respond faster and more smoothly. Brushless servos are the most efficient, last the longest, and deliver the most torque, but they’re also the most expensive.

Waterproofing

If you drive in wet conditions, through puddles, or in snow, choose a waterproof servo. A waterproof servo is sealed with O-rings and a coating on the electronics. Keep in mind, though: “water-resistant” doesn’t mean you can take it diving.

Size and spline

Servos come in different sizes: standard (most 1/10 and 1/8 cars), low-profile (shorter, for racers), mini, and micro. Check the dimensions of your car’s servo mount before ordering. Some models, such as certain Traxxas cars, use a proprietary servo size or mounting system.

Each servo also has an output shaft with a specific number of teeth: the spline. 25T is the most common, but 23T and 24T versions are also available. Always use a servo horn with the correct spline, preferably a metal horn for powerful servos.

Protect your servo: the servo saver

A servo saver sits between the servo and the steering linkage and absorbs impacts, preventing the gears in your servo from breaking. On crawlers, the servo saver is often replaced with a rigid horn for greater precision. We recommend one for bashers and racers.

Conclusion

The ideal servo balances torque, speed, and price to suit your car. For a crawler, choose as much torque as possible; for a racer, prioritize speed; and for a basher, choose a sturdy all-rounder with metal gears that can take a beating. Don’t forget to check that your ESC can supply enough power to the servo.

Browse our full range of servos, or read our article about upgrading your RC car’s electronics.