The engine is noisy: when is this normal and when is it not?
An electric bike motor always makes a little noise. But not all noises are normal. In this guide, I'll explain which sounds are normal, which are not, and how you can determine for yourself whether it's time to take action.
Written by: Hanna Stevens | January 8, 2025 | Reading time: 6 minutes
More about the author: Hanna Stevens
Hanna is an avid cyclist who loves exploring new routes and sharing her experiences to inspire others to get on their bikes more often.
Key findings
- A slight humming noise is normal, but squeaking or howling noises are not.
- Many "engine noises" actually come from simple or loose parts.
- Early intervention can prevent significant damage.
Why does an engine make noise?
Before addressing the issues, it is important to understand that all electric bike motors produce some noise when operating. This is due to a combination of factors:
- Internal components: bearings rotate, shafts move, and, on some motors, gears mesh together.
- Electrical vibrations: Variable magnetic fields cause the coils to vibrate slightly. This results in a buzzing or whistling sound.
- Frame resonance: The frame can sometimes act as a sound box. Lightweight frames, in particular, amplify certain frequencies.
What I personally find interesting is that researchers have discovered that it is not so much the volume that bothers us, but the pitch of the sound. High-pitched noises irritate our brains much more quickly than low-pitched sounds, even at the same intensity.
Good (normal) noises
Don't worry if your bike isn't completely silent. The following sounds are typical of an e-bike in good working order:
- Low humming noise when starting: mainly audible when starting or accelerating. This is simply the engine delivering power.
- Slight clicking noise in freewheel: when you stop pedaling, you may hear a slight rhythmic ticking noise. This comes from the freewheel.
- More noise under heavy load: when climbing hills, with full panniers, or at maximum assistance, the motor works harder and becomes more audible.
- A little more noise in cold weather: at low temperatures, grease and components are stiffer. After a few minutes, the noise usually subsides.
Motors with gears naturally make a little more noise than those without gears. This often sounds like a slight whistling noise that increases with speed. This is normal. Personally, a slight humming noise reassures me; total silence sometimes gives the impression that the motor is "doing nothing."
"Bad" noises (when action is needed)
When does a noise go from being "characteristic" to " problematic "? Watch out for the following signs:
1. Squeaking and rubbing
This is one of the most common and serious noises. A squeaking noise, like metal against metal, often indicates worn bearings. Bearings allow internal components to rotate smoothly; when they are worn or dirty, the noise is clearly audible, even when turning the wheel by hand. Sand or dirt may also have entered the motor housing, causing a grinding noise.
2. Loud rattling or knocking noises
Do you hear a rattling noise, especially on uneven ground? This almost always indicates loose parts. Vibrations can cause engine bolts, wheel nuts, or even casing screws to loosen over time. A poorly secured engine can cause serious damage to the frame if not repaired.
3. High-pitched, shrill, or whistling noise
A whistling or high-pitched scream may indicate dry parts requiring lubrication, or wear on internal gears in transmission motors. Many motors use nylon gears to reduce noise; when these wear out or break, the soft hum turns into a loud screech or crackling sound.
4. "Hiccups" or irregular operation
If the motor seems to be stuttering, coughing, or running unevenly, the problem is often electrical rather than mechanical. This may be due to a poor connection between the motor and the controller, or faulty Hall sensors (which determine the position of the motor). This phenomenon is often accompanied by a loss of power.
Possible causes
To solve the problem, you need to understand its cause. Here are the most common culprits:
Mechanical wear
- Gears: In gear motors, nylon gears wear out after thousands of kilometers or under heavy use. A lack of grease increases friction and noise. Replacing the gears and adding grease can restore the motor to new condition.
- Bearings: These wear out over time and with exposure to water and dirt. A worn bearing causes a constant humming or squeaking noise that intensifies with speed.
Electrical problems
- Controller type: Did you know that the type of controller affects noise levels? A square wave controller produces a harsher, rougher hum, while a sine wave controller delivers power more smoothly and is therefore much quieter. Have you recently replaced your controller with a cheaper model? This could explain the increase in noise.
- Hall sensors: if they are defective or poorly connected, the engine does not know exactly when to deliver power. This results in vibrations, irregular noise, and jerky driving.
Loose parts
- Spokes: An often overlooked cause of "engine noise" is actually the wheel itself. Loose spokes can produce a rhythmic, rubbing, or rattling noise, often mistaken for an internal engine problem.
- Fasteners: If the axle nuts are not tightened sufficiently, the entire motor may vibrate in the frame.
Action plan for diagnosis and solution
Did you hear a strange noise? Follow these steps before rushing to the bike shop.
Step 1: Listen and locate
Turn on the bike and lift the wheel equipped with the motor (using a kickstand). Gently activate the assistance. Listen to where the noise is coming from. Is it constant? Does it change with speed?
Step 2: Manual inspection
Turn off the bike. Spin the wheel by hand.
- Do you still hear a squeaking noise? It's probably a mechanical problem: bearings, brakes rubbing, or dirt.
- Does the wheel turn silently by hand, but make noise as soon as the motor is activated? The problem is then probably electrical (controller, Hall sensors) or related to the internal gears, which only protest under load.
Step 3: Visual inspection and tightening
Check all bolts and nuts around the engine. Tighten the engine bolts, axle nuts, and fender fasteners. Also check the tension of the spokes; loose spokes can cause a rattling noise that sounds like an engine problem.
Step 4: Eliminate external causes
Sometimes the engine is blamed unfairly.
- Brakes: Dirty or misaligned brake pads can emit a high-pitched squeal.
- Chain: A dry or rusty chain may crack and squeak. Lubricate it and check if the noise disappears.
- tires too low pressure increases resistance and noise.
When should you call in a professional?
Even though many things can be done yourself, such as cleaning or tightening bolts, some situations require professional help:
- In case of persistent squeaking indicating damaged internal bearings or broken gears.
- In the event of electrical problems, such as error codes on the display or a motor that jerks and cuts out.
- If the engine casing needs to be opened and you do not have the necessary experience. Opening the engine may, in some cases, void the warranty.
Prevention is better than cure
The best way to keep your engine quiet is to maintain it regularly. Keep your bike clean, especially after riding in the rain or sand. Lubricate the chain regularly and check every month that all bolts are tight.
An electric bike motor is a marvel of technology, designed to give you years of riding pleasure. By paying attention to the sounds it makes, you can solve minor problems before they turn into costly repairs. So, the next time you hear a strange noise: turn off the music, listen carefully, and play detective with your bike.
FAQ
new a buzzing noise on a new e-bike normal?
Yes, new engines often hum a little more until the components are broken in.
Can rain cause more engine noise?
Yes, moisture and dirt can temporarily increase noise, especially in the bearings.
Is a mid-drive motor always quieter than a hub motor?
Not always. It all depends on the design, the controller, and the frame.
Can I open the motor of my electric bike myself?
Technically yes, but this often voids the warranty.
How can you tell if the noise is coming from the engine or the wheel?
By turning the wheel by hand when the bike is turned off.