Noise from rear hub when going 21mph+

[Danny Troy]

I have a step-thru 2.0 and an XP 2.0. On my XP when going approximately 21-22mph and over (although only goes to 24mph) I get a grinding sound coming from the rear hub. This is on a flat surface, with no headwind. I weight about 165 lbs. I made a video and posted it on YouTube. I sent the link to tech support but they suggested it might be a loose fender. The sound immediately stops when letting off the throttle, so I really don't think it's the fender. I could swap controllers, but I'm saving that as a last resort. Here's a link to the video. The sound start at about the :17 sec mark:

 

[BigNerd]

Tried turning the bike upside down and trying to reproduce?

It does sound like something at that speed is scraping something.

 

[Danny Troy]

That's a good idea. I might try that. That way I could really pinpoint where the noise is coming from. The thing is, when going downhill over 22mph and I let off the throttle the noise isn't there. BTW, I checked for loose bolts and everything is tight, so I double it's the fender or anything loose.

 

[Deerdog]

Mine made a noise at a certain point. Took a while to find it but it was the finder. Made a gasket out of an old bycicle intertube noise went away.

 

[ki11a]

Yep, sounds like the fender reverberating from the motor vibrations. Fairly common.

 

[Danny Troy]

Yep, sounds like the fender reverberating from the motor vibrations. Fairly common.

I elevated the bike so I could use the throttle and I didn't hear any noise, even at full throttle. I suppose it only appears when under load. I'm thinking it's coming from the hub motor. One way to solve this is to swap wheels with my wife's step-thru. She will never go over 20mph (probably not faster than 15mph!) so that might be a good way to go. Question is, how easy is doing a wheel swap?

 

[Deerdog]

Take the fender off and see if it still makes the noise

 

[Danny Troy]

Take the fender off and see if it still makes the noise

OK, easy enough. I'll give that a try. Thanks!

 

[rich c]

Kind of thinking it might be the brake rotor? It's a bit similar sound when you apply the brakes to stop.

 

[Danny Troy]

Kind of thinking it might be the brake rotor? It's a bit similar sound when you apply the brakes to stop.

I hear what you hear, but that's not the sound that I'm talking about. I guess you can say there's two sounds happening simultaneously. I'm waiting to hear from the company. I know they don't want to offer a solution that won't cost them money, so they had told me to tighten all fender bolts, which were already good and tight. If I find the time I may swap wheels and or controllers with my wife's step-thru.

 

[someguy272]

I just received a lectric xp 2.0 step through with the same rear hub noise over 21mph+, contacted their customer support, they dismissed it and said that was normal, really?? Did anyone find a solution for this issue, please advise?

 

[Danny Troy]

I just received a lectric xp 2.0 step through with the same rear hub noise over 21mph+, contacted their customer support, they dismissed it and said that was normal, really?? Did anyone find a solution for this issue, please advise?

I was fortunate in that I was able to swap wheels with my wife's step-thru. I still haven't totally tested it, but so far it appears the noise is gone on my bike and still there, but less noticeable, on my wife's bike. Definitely got me scratching my head. Since my wife will never go above 20mph it's a moot point for me. My bet is the info in this link is likely the cause.
https://endless-sphere.com/forums/viewtopic.php?t=95478

 

[someguy272]

When I reached out to customer support about his issue, they indicated as normal and dismissed.

 

[rawlus]

could be normal/expected. unsure. i don’t know what the innards of the motor are but could just be internal components and harmonics at certain speeds right?

 

[Danny Troy]

could be normal/expected. unsure. i don’t know what the innards of the motor are but could just be internal components and harmonics at certain speeds right?

I still haven't thoroughly tested the bike, but when I did test it I heard the noise, but not as bad. Could be something inherent in the motor when pushing it above 20mph. I can live with it as is, as long as it doesn't get worse. On the upside, I became proficient in taking off the rear wheel, so I'm all ready to fix a flat, if I get one!

 

[BoomChick]

I have a step-thru 2.0 and an XP 2.0. On my XP when going approximately 21-22mph and over (although only goes to 24mph) I get a grinding sound coming from the rear hub. This is on a flat surface, with no headwind. I weight about 165 lbs. I made a video and posted it on YouTube. I sent the link to tech support but they suggested it might be a loose fender. The sound immediately stops when letting off the throttle, so I really don't think it's the fender. I could swap controllers, but I'm saving that as a last resort. Here's a link to the video. The sound start at about the :17 sec mark:

I have a step-thru 2.0 and an XP 2.0. On my XP when going approximately 21-22mph and over (although only goes to 24mph) I get a grinding sound coming from the rear hub. This is on a flat surface, with no headwind. I weight about 165 lbs. I made a video and posted it on YouTube. I sent the link to tech support but they suggested it might be a loose fender. The sound immediately stops when letting off the throttle, so I really don't think it's the fender. I could swap controllers, but I'm saving that as a last resort. Here's a link to the video. The sound start at about the :17 sec mark:

 

[BoomChick]

Hi Danny., I joined this forum because of how exactly your post describes the same issue with my new
Lectric 2.0 ST.
So ... Thanks! (I had never joined any forums)
Mine sounds the same at the same speeds, and also does not go 28 mph (probably due to the smaller diameter tires). Also, the back tire is Lop sided, and I was unable to true it out. Lectric CS also gave me the run around, as in it's "normal".
My bet is, we got a bad batch just as described in your attached Endless Sphere post. Thanks for that great info.
Eventually, I will disassemble the motor and see if I can epoxy the magnets as suggested. But first, I will try Lectric CS again to see if they will send me another wheel. I really doubt it, but I'll keep you informed. I wounder how many others are having the same issue?

"Endless Shere"

Re: High speed geared hub motor noise.​

• Quote

by justin_le » Nov 04 2018 6:57pm

FWIW, this is a case where one of the magnets has become unbonded from the rotor and at high RPM's the centripetal force throws it against the stator where it scrapes around, and not related to the gears. When the motor is spinning more slowly, the magnetic force holding it to the rotor is strong enough to keep it in place but once you hit that critical speed it will fling out again. If you stop at that point and then glue the magnet back with epoxy it's normally fine. But if you continue running it with this scraping noise the friction will eventually cause the magnet to overheat and demagnetize.

LooseInrunnerMagnet.jpg (110.06 KiB) Viewed 963 times
Normally this happens somewhere around 600-700 rpm, but we've found that the magnet bonding from Bafang has been fairly hit and miss and we had one entire shipment of motors where we had to open up and remove/reglue all the magnets since this would happen even at what we consider normal operating RPMs (350-400).

In Bafang's defense they would normally sell these motors with voltages and windings for 24kph EU pedalecs where the hub doesn't spin at more than 200rpm (corresponding to 2200 rpm on the motor) and the g forces are modest enough. Centripetal forces increase with the square of the RPM so when you double the speed that's 4 times the G forces on the rotor magnets.

 

[someguy272]

Same issues here with the same generic response from Letric customer service reporting it is normal and dismissing me. How did this company get so much praise when you see this same scenario repeating itself with no assistance or warranty of lack of? They market well but do they do anything else well?

 

[BoomChick]

Hey Guys,
Thought I'd post the email I sent to Lectric for your info. I will let you all know if anything comes of it.
If nothing happens, I will be looking at replacing this with a different ebike brand.
Also, I wanted to thank you all for the great video's and articles on this hub motor issue. THANKS!

Dear Lectric Crew,
I never heard back from you all about the lop sided rear wheel.
In the meantime, I've noticed other issues with the rear wheel.
When going approximately 20 mph and over, I get a grinding sound coming from the rear hub. This happens while under load only. I've checked everything, all bolts, breaks, fenders etc. and all are good and tight.
After much research, I'm almost positive that the rear hub motor has some loose magnets. Please see attached...>

What I would like ... is for you to send me a new good hub/wheel.
Then, I will replace mine, and return to you the defaulty wheel.

Thank you,
Brooks,
970-541-1230
Order #100863

THIS IS THE SOUND IT MAKES:

LIKELY PROBLEM:
https://endless-sphere.com/forums/viewtopic.php?t=95478#p1423266

 

[someguy272]

Let me know how that works out for you, I have the same issue with noise, calling didn't resolve anything.