Why Your RC Car Is Going Slow All Of A Sudden.

Have you ever been in the situation where you’ve taken you RC car out and its slowed down all of a sudden? Panic sets in and you’re not sure what to do? Whether its a simple fault or something more serious, I’ve done some research to make this helpful post to find out.

If your RC car is moving slowly all of a sudden, it could be from one of the following issues:

  • A burnt-out motor from driving through grass or doing tricks.
  • The battery is not fully charged.
  • The type of battery you are using.
  • A loose slipper clutch.
  • The mode of your ESC.
  • A poor connection.
  • The drive train is binding.
  • The engine is poorly tuned and needs breaking in.
  • The motor is over-geared.

The above are just a few possible issues that could slow down your RC car. After reading this article you will be able to identify and solve any of the many issues that can slow down your RC vehicle.

Let’s start with some common but simple issues that can be checked and solved with ease.

There are some easy checks you can do to solve the issue.

Check to see if the battery is fully charged. Try another battery on your car that you know is fully charged and see if the problem is solved. You should always charge your batteries the day that you are going to use your vehicle, they can lose some of their charge when left without use for a while.

There could be a poor connection from the motor or the battery. Poor connections restrict the transfer of power so check the motor connectors and battery connectors for poor or damaged connections. Check the solder joints for any damage and repair or replace if needed.

A poor connection could be from storing your RC vehicle for a while after running through wet conditions. If you didn’t allow your car to fully dry out before storing it, this could cause rust to the connectors.

You may be interested in reading my article; How, Where and when to store RC trucks

Check the ESC. An ESC, electronic speed controller, regulates the power of an electric motor, there are different ones for brushed motors and different ones for brushless motors but both types work on the same principle. Your ESC could be in training mode. Training mode reduces the power on most models by 50 per cent, change your ESC back to normal mode and your car will be back to full power again.

You may find my article on how to tell if your ESC is bad useful

The electronics on your RC car may be hot. Let your car cool down between runs.

Take a look at my article; 13 reasons why rc motors and ESC’s burn up

If none of the above gets your RC car back to full speed, its time to look more in-depth to solve the issue.

How And Where Have You Been Driving Your RC Vehicle?

The conditions and how you have been driving your RC vehicle could have an impact on the performance of your vehicle.

For example, let’s say you’ve been running your car through grass at full throttle, there’s a chance the motor could be over heating, causing damage to the armature and windings.

We all like pulling cool stunts with our vehicles but anything where your cars just rolling and suddenly going full throttle to attempt something like a cool wheelie can damage the motor.

If your car is still running slow, there are more checks that can be done. Let’s look at all the possible issues that could be factors in slowing your RC car down.

Issues That Can Slow Down Your RC Vehicle

Your motor could be dirty causing your car to go slower. A well-maintained motor helps your car’s performance and helps the motor to last longer. Always check your motor after taking your car for a run and give it a clean and oil it afterwards.

Check out my article on how to clean and maintain a brushed rc motor

For nitro RC cars, if the engine is new or poorly tuned, it will require a break-in. Refer to the instructions from the manufacturer on how to do a break-in and how to tune it, or seek help from an expert.

Over gearing can cause your car to slow down. A hot motor could be a sign of over gearing. Try a smaller pinion gear to reduce the load the motor has to handle or a different size spur gear.

Watch this helpful video to understand more about gearing your RC vehicle.

If the motor is damaged in any way, replace it straight away.

Check the drive train to see if it’s binding. You can check to see if the drive train is binding by removing the motors pinion gear and roll your car on a flat surface.

There’s a chance that the motor has reached the end of its useful life, If you know the drive train, gearing and the battery is good then its a sign you need to replace your motor.

You could have the wrong lipo battery for the type of motor you have. Lipo batteries come with a C rating, basically put, if your using a low C rated battery for a decent motor then it’s not going to give the motor what it needs to run fast. If you can’t find any info for which C rating you need for the motor then you must contact the manufacturer to find out.

Having the correct battery will avoid a lot of problems in the future.

Here are a few more things to check if you’re having problems with your RC car;

  • A missing axle drive pin. If one of these is missing, power won’t be transferred correctly to the wheel resulting in little or no movement of your car.
  • Speed control or resistor could be burnt out. Replace the resistor if it’s damaged. If the resistor is ok, replace the speed control.
  • Check the drive belt for loose tension and make necessary adjustments or replace if there are any missing teeth.
  • Tires slipping on the rims. Make sure your tires are glued on properly.
  • Damaged gears. Check the transmission gears and the spur gear for any missing teeth, and replace if necessary.
  • Check the brakes to see if they are binding. If there’s no damage, make some adjustments so they work correctly.
  • For nitro cars, the slipper clutch may be loose and needs tightening. Also, check for worn-out clutch shoes and replace if necessary.

Is The Set-Up Slowing your RC Vehicle Down?

The set-up of your car plays a huge factor in the way your car performs.

There are so many mistakes you can make trying to get your RC car to go as fast as it can that you could end up with your car performing the opposite of what you want to achieve and could end up being rather costly if you don’t have a full understanding in what you are doing.

For example, just buying a stronger motor wont make your car any faster unless the other parts on your car are set up correctly.

The idea is to get the right combination of the different parts on your car so it can perform to its best, but just one mistake will hinder your efforts.

Watch this helpful video to give you an idea of what’s involved so you can avoid slowing down and damaging the components on your RC car.


You now know that after a few simple checks, you could have your RC car running back to normal in no time at all, and if it’s still running slow, you know where to check and what to adjust or replace to fix it.

Its really important that you know what you are doing with your car if you want to do an upgrade or change the set-up and how easy it could go wrong if you make a mistake.

RC cars are so much fun and messing around with how they work is all part of the enjoyment that we have with them, but always check the manual, contact the manufacturer or seek help from an expert if you’re not 100 percent sure in what you are doing.

Paul Good

This awesome hobby has something for everyone, whether you like to build your RC from scratch and keep modifying till you've got it to just how you want it, to track racing. You might be out with a boat, or perfecting your skills with a plane. Are you taking some cool pics with your drone? I'm sure my site will help you on your journey.

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