Home › Problems without a code › E-bike motor making grinding or clicking noise
Grinding or clicking from the e-bike motor? Where the noise comes from and what it means
Most 'motor' noises are not the motor at all: chainline, a loose chainring lockring, a dry freehub, or a rotor rubbing all get blamed on the drive unit. Isolate the noise by testing with and without pedalling, with and without assist, before assuming the worst.
Quick checks, in order
- Ride with the assist off and listen. Noise still there means it is mechanical (chain, gears, bearings, brakes), not the motor.
- Lift the rear wheel and spin it by hand. Rubbing or ticking once per revolution is a rotor, a magnet touching the speed sensor, or a spoke.
- Backpedal the cranks. A click or grind while backpedalling is the freewheel or freehub, or on Bosch a dry sprag clutch in the drive unit, and not a motor fault.
- Check the chainring lockring and the chainring bolts. A loose lockring on Bosch and Shimano drive units clicks under load and is the most common 'motor noise' in a workshop.
- Look at the chain and cassette. A worn chain on a new cassette, or a dry chain, grinds under motor load and sounds like it is coming from the unit.
- Use walk assist with the rear wheel lifted. A rhythmic grind or a metallic rattle that only appears when the motor drives the wheel is inside the motor or the reduction gears.
- On hub motors, spin the wheel with the motor off and listen for a rough bearing; then use the throttle or walk assist at low speed and listen for a rattle that follows motor speed.
Likely causes
Loose chainring lockring or spider (mid-drive)
How to tell: Click or knock under pedalling load, worse when standing on the pedals, silent with the motor off but still pedalling lightly.
Fix: Tighten the lockring to spec with the correct tool (Bosch and Shimano use their own). Grease the threads. If it keeps loosening, the spline or the ring is worn.
How to tell: Click or knock under pedalling load, worse when standing on the pedals, silent with the motor off but still pedalling lightly.
Fix: Tighten the lockring to spec with the correct tool (Bosch and Shimano use their own). Grease the threads. If it keeps loosening, the spline or the ring is worn.
Worn or dry drivetrain
How to tell: Grinding under motor load in certain gears, chain skips, cassette teeth hooked.
Fix: Measure chain wear; e-bike chains wear fast. Replace chain and cassette together if the chain is past 0.75 percent.
How to tell: Grinding under motor load in certain gears, chain skips, cassette teeth hooked.
Fix: Measure chain wear; e-bike chains wear fast. Replace chain and cassette together if the chain is past 0.75 percent.
Freehub or freewheel worn (hub-drive and mid-drive)
How to tell: Clicking or grinding when coasting or backpedalling, sometimes the cassette body wobbles.
Fix: Service or replace the freehub body. On hub motors with a threaded freewheel, replace the freewheel.
How to tell: Clicking or grinding when coasting or backpedalling, sometimes the cassette body wobbles.
Fix: Service or replace the freehub body. On hub motors with a threaded freewheel, replace the freewheel.
Hub motor clutch or nylon reduction gears failing
How to tell: Geared hub motor makes a grinding or ratcheting noise only when powered, sometimes with a loss of drive. Common on cheaper hub motors after water ingress or high loads.
Fix: Motor opening and gear replacement. Some shops do this; otherwise replace the motor.
How to tell: Geared hub motor makes a grinding or ratcheting noise only when powered, sometimes with a loss of drive. Common on cheaper hub motors after water ingress or high loads.
Fix: Motor opening and gear replacement. Some shops do this; otherwise replace the motor.
Bearing failure in the drive unit or hub motor
How to tell: Rumbling that follows crank or wheel speed, felt through the pedals, worse over time. Play at the crank axle.
Fix: Mid-drive: bearing replacement at a specialist or drive unit exchange. Hub motor: axle bearings can be replaced by a competent shop.
How to tell: Rumbling that follows crank or wheel speed, felt through the pedals, worse over time. Play at the crank axle.
Fix: Mid-drive: bearing replacement at a specialist or drive unit exchange. Hub motor: axle bearings can be replaced by a competent shop.
Debris inside the motor or against the rotor
How to tell: Sudden new noise after riding through gravel or sand, scraping once per wheel revolution.
Fix: Check between the rotor and the caliper, and inside the chainring guard. On hub motors a stone in the motor cover gap is common.
How to tell: Sudden new noise after riding through gravel or sand, scraping once per wheel revolution.
Fix: Check between the rotor and the caliper, and inside the chainring guard. On hub motors a stone in the motor cover gap is common.
Bosch sprag clutch dry (Performance Line / CX)
How to tell: Clicking or a soft grinding when pedalling with the motor off or backpedalling; disappears under motor load.
Fix: Known behaviour; a dealer can re-grease it. It is not urgent unless the drive slips.
How to tell: Clicking or a soft grinding when pedalling with the motor off or backpedalling; disappears under motor load.
Fix: Known behaviour; a dealer can re-grease it. It is not urgent unless the drive slips.
By drive system
- Bosch: Lockring first, always. Then check the sprag clutch (click when backpedalling is not a fault). Bosch CX Gen 4 units have a known rattle from the crank axle at low speed that is cosmetic. A grinding under power with a hot unit is bearing failure; DiagnosticTool will not show it, a mechanic will.
- Shimano STEPS: Shimano E8000/EP8 lockring and the chainring interface loosen; retorque. EP8 units can develop a rattle from the internal ratchet that Shimano addressed with a firmware and clutch update; a dealer can check the serial. Grinding on the drive side that follows crank speed is the bottom bracket bearing.
- Bafang: BBS mid-drives use a nylon primary gear that strips under heavy load or when the clutch slips; you hear a grinding and lose drive. Replacement is a shop job. A clicking under load is often the chainring bolts or the secondary reduction. Bafang hub motors grind when the planetary gears or the clutch wear.
- Yamaha PW: Yamaha PW units are quiet; a new grinding or knock is usually the chainring or a worn bottom bracket bearing inside the unit. Yamaha units can have the crank axle bearings replaced by a dealer without a full exchange.
- Generic: Geared hub motors: a grinding that only appears under power is the nylon gears or the clutch. Direct-drive hubs are almost silent; a scrape there is a magnet or a bearing. Check the axle nuts are tight; a hub that has spun in the dropouts grinds the cable and can shear it.
When to stop: Stop riding and get it checked if the noise comes with a loss of drive, a hot motor casing, metal particles, or play in the crank or wheel axle; a failing gear can lock the drive without warning.
Related error codes
Still stuck? Take a photo of the display and show it to a local e-bike workshop. Bring the bike's system name (e.g. Bosch Performance Line CX) and the exact code; that saves diagnostic time and money.
Frequently asked
My Bosch motor clicks when I backpedal. Is it failing?
No. That is the sprag clutch and it is normal, more noticeable when it dries out. A dealer can re-grease it if it annoys you.
The noise only happens in certain gears.
Then it is the chain, cassette, or chainline, not the motor. Check for a bent hanger and chain wear.
Is a hub motor grinding noise fixable?
Often yes. Geared hub motors have replaceable nylon gears and a clutch; a good shop can rebuild them. If the motor was a cheap one, a new motor can be the cheaper route.