Clicking/knocking sound Bosch CX Gen 4 motor

joejoejoe

New Member
Jun 7, 2024
5
1
Yorkshire
Hi
I have a Bosch CX Gen 4 motor on a Cube Stereo Hybrid 160 HPC. It has developed a moderately loud clicking/knocking noise when the left crank is at 7 O’clock this only happens under load and ONLY when the bike is switched on, it is silent when the bike is turned off. Have you any ideas what the issue is and if so is it an easy or difficult fix?
I would be grateful for any help you can offer.
Joe
 
Last edited:

Stihldog

Handheld Power Tool
Subscriber
Jun 10, 2020
3,060
4,270
Coquitlam, BC
There’s a few simple things you can do before a motor repair or replacement.
Check your motor mount bolts(6). Check the peddle shafts. Remove the chain and spin the crank. Listen for noise. Insure the crank(s) is torqued correctly.

A LBS can definitely help with the issue but the Bearing Man may be able to fix the motor rather than a replacement.
 

joejoejoe

New Member
Jun 7, 2024
5
1
Yorkshire
It only makes the noise when the bike is powered ON and under load and clicks/nocks at exactly the same point on each revolution of the crank, no noise at all when the bike is ridden switched off no matter how hard you pedal. The brackets and mounting bolts have all been checked. The motor has been removed and refitted twice.
 
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Stihldog

Handheld Power Tool
Subscriber
Jun 10, 2020
3,060
4,270
Coquitlam, BC
Sounds like a mystery. If it’s an internal motor issue, your LBS or bearing man may be able to diagnose the problem. That sound would drive me crazy too 😜
 

Mikerb

E*POWAH Elite World Champion
May 16, 2019
6,234
4,728
Weymouth
I know you say the conditions under which it happens but a noise at one point of crank rotation is weird! Are you sure the right side crank or chainwheel is not hitting the chain guide??
 

Neeko DeVinchi

E*POWAH Elite World Champion
Dec 31, 2020
1,011
1,340
UK
Not too sure if it helps but have you tried taking the crank off, cleaning the splines on the motor and the crank, adding grease and installing?

I've encountered similar issues on ebikes where you have an alloy crank. 9/10, the problem is resolved👍🏿
 

joejoejoe

New Member
Jun 7, 2024
5
1
Yorkshire
It has been with the bike shop for over a month now they have removed and refitted the motor several times. The noise must be coming from the motor as it is ONLY PRESENT WHEN THE BIKE IS SWITCHED ON. They are wanting to send the motor to Bosch which they say may take a couple of months.
I tried the bearing man first but he thought the noise was coming from a loose motor bracket and that there is nothing inside the motor that would cause a regular clicking noise. I find this VERY odd as I explained there is no noise at all when the bike is switched off no matter how much torque you put through the pedals. Surely there is much more stress being put on the motor, mountings frame etc when the motor is OFF and the bike is pedaled hard?
I have asked them to try the motor on a different bike which they are going to do today.
 

Keifo H

Member
Dec 20, 2019
12
8
Chesterfield
Had the same thing a couple of years ago on a trek rail, tried everything before I went down the motor route , removed chain guide , checked cranks, chainring nut , motor mount bolts , pedals ,wheels, suspension pivots , gorpro'd the noise whilst pedalling up a hill , LBS replaced under warranty , had no loss of power or fault codes , motor worked well, just knocked.
 

markloch

Active member
May 14, 2021
145
119
NorCal
Had the same thing a couple of years ago on a trek rail, tried everything before I went down the motor route , removed chain guide , checked cranks, chainring nut , motor mount bolts , pedals ,wheels, suspension pivots , gorpro'd the noise whilst pedalling up a hill , LBS replaced under warranty , had no loss of power or fault codes , motor worked well, just knocked.

Ditto. It was the coming from the left side, definitely position-dependent, pedal at 10–11 (when facing non-drive-side). It didn’t require load on the pedal to cause it to click. I’m not sure if I also felt it in my foot or just an aural haptic effect. I made a video of it and showed it to the Trek shop. I also felt the slightest amount of play in the spindle that wasn’t present in other motors. That seemed to be enough for Bosch to replace the motor. I brought it in a week before the warranty expired (this was a year ago).

Someone told me that the warranty resets when a motor is replaced … anyone know if this is true? And If so, is it documented somewhere?
 

Wilko58

Member
Nov 24, 2020
102
88
Chorley
Someone told me that the warranty resets when a motor is replaced … anyone know if this is true? And If so, is it documented somewhere?
I've had my Whyte e-160s since 2020 and follow lots of groups.
Although I can't find it documented, I can say that initially the warranty did begin again when a new motor was fitted but over the years I noted that people were posting that this had changed and the warranty date stays as the original warranty date.
 

Bearing Man

Ebike Motor Centre
Patreon
Sep 29, 2018
889
2,123
UK
It has been with the bike shop for over a month now they have removed and refitted the motor several times. The noise must be coming from the motor as it is ONLY PRESENT WHEN THE BIKE IS SWITCHED ON. They are wanting to send the motor to Bosch which they say may take a couple of months.
I tried the bearing man first but he thought the noise was coming from a loose motor bracket and that there is nothing inside the motor that would cause a regular clicking noise. I find this VERY odd as I explained there is no noise at all when the bike is switched off no matter how much torque you put through the pedals. Surely there is much more stress being put on the motor, mountings frame etc when the motor is OFF and the bike is pedaled hard?
I have asked them to try the motor on a different bike which they are going to do today.
Although it is not impossible that this noise is coming from the motor, it is normally unlikely. Most components inside the motor rotate at a different speed to the pedals, so the only thing inside the motor that revolves at the same speed as the pedals is the crankshaft. Everything else is geared from the crankshaft and rotates faster or slower, this presents the noise in a different place, each time the pedal is rotated.
It is almost always the case that these noises disappear when the motor is switched off because no matter how hard you pedal, you have removed the extra 300 to 400% of extra power that the motor would supply, removing much of the twisting forces required to make such a noise.
There is nothing but two bearings and the crankshaft rotating at pedal speed, and bearings don't usually click or knock. This is why we tell people to check the motor mounts, crank arms, spider nut, spider to chainring bolts, pedals, seat post, suspension linkage, rear cassette, freewheel hub, rear axle... etc.
If nothing is found, then it's time to look at the motor.
 

RustyMTB

E*POWAH Elite World Champion
Jul 22, 2020
2,643
6,439
UK
I had a clicking I was convinced was the motor until I traced it to a bad freehub bearing. the thread in here ran to four pages. anyway, the lbs should have put in another bike by now, which should answer things, no?
 

GrantCube

Member
Mar 26, 2020
26
49
Sydney, Australia
I have the exact same problem and Bosch have said it is not the motor....I have had the noise on the same bike as the OG....Cube Stereo 160, for about 2 months and it deosnt seemt o do anything other than make a noise.....LBS have heard it and are equally confused....will check free hub bearings but they should be OK...the rear wheel was built up from new only months ago wiith all new components.
 

joejoejoe

New Member
Jun 7, 2024
5
1
Yorkshire
New motor was fitted under warranty last week and I've done around 200 miles without any clicking/knocking noises. The LBS didn't do any work to investigate which part of the motor was at fault but Bosch replaced it without question or any explanation. So I am guessing Bosch know what the issue is. The motor had only done 450 miles from new.
 

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