Weird tram sounds on my ebike.....

I hope to find a super-knowing-mechanical-physical-hero about bikeframes here on ES

My Problem is a weird "swinging" sounds like a tram on exact speeds from 23 to 24kph.
You can hear it best on very low loads.
it is NOT THE MOTOR. Why iam sure? Iam sure because i had a bafang 500w installed before and i get the SAME sounds on SAME speed :-/
The Spokes are all stiff tightend.
(Yes i know my Brakingdisc is wobbling )

yesterday is made a video. so here it is.


[youtube]ltBc0E8Tn7I[/youtube]

I am not entirely sure which sound you are referring to. Is it the higher pitched sound (I don't know what a tram sounds like)? Have you tried riding without the rear disk brake in place?

I hear the normal "grunting" sounds of the phases firing. That's the lower pitch buzzy sound.

But there is an intermittent warbly sound too. I'm thinking it's the disk or pad chirping. Sounds a bit like if you ran the bike in reverse, it would say "Paul is dead" over and over. If you aren't old you won't get that one.

Could also be something else on the hub rubbing. tire, or maybe a freewheel with a tight clearance rubbing the hub cover.

Could even be a bad bearing, but only the disk would have been the same on the other motor right?

Yep. Sounds like brake pads rubbing to me too.

i wish it were the brakepads.
i can reproduce it on a bikestand. just rearbrake 300w and pass the 23-24kph line you will hear the sound.

the sound isnt normal.
i rode this also without disc mounted.

here is the sound on another 500w geared bafang. i think you will hear that sound a lot better.
listen at :050 starting.

[youtube]RIa_LAux-go[/youtube]

Well, if you are absolutely certain it isn't the disc brake, then my second guess would be something shaking or shivering loosely. Maybe a washer in a bolt with a nylon nut or a thread locker not quite tight enough. Something vibrating at just that specific frequency. It's clearly unappealing, that is for sure. One of the wonders of an ebike, it's so quite we can worry about a sound as docile as that. Contrast that to the weed whacker volume of an ICE motor, WRRRRRRRRRRRRRRRRRRRRRR. "WHAT? I CAN'T HEAR YOU!?"
I am sure you've considered tightening everything, I'd be surprised if you haven't at least, but I'd give everything a once over, unscrew each nut a bit, see what you can learn, shake things around, maybe a spray of oil, and then tighten, you may even trial and error over and over with each nut/bolt. That is what I've done a couple times. It sucks, it's tedious as hell, but it'll pay off to know for your peace of mind. Instead of thinking that sound is your bike about to fall apart, it was one of four non-critical bolts. Maybe consider taking off things and going for a ride, if you can.

It's great that you know it's not the motor though, that'd be a pain to try and troubleshoot.

Tires rubbing the fender then perhaps.

Lots of different sounds here.

Does your motor mainly make this sound when you've let off the throttle? sounds like a noisy clutch and gears..

Any progress or updates on your strange sound?

dogman said:

Tires rubbing the fender then perhaps.

Click to expand...

rubbing only at 23-24kph?

neptronix said:

Lots of different sounds here.

Does your motor mainly make this sound when you've let off the throttle? sounds like a noisy clutch and gears..

Click to expand...

the second video was with the "Old" Motor. It is a Geared Bafang.
But now i have the 3540HS ....no Gears....same Sounds.

bowlofsalad said:

Any progress or updates on your strange sound?

Click to expand...

not really. no freetime to work around.
Next week iam Upgrading to a 4080. On this "event" i will replace the 9x freewheel for testing.

....strange in any way.....

4080 in 26" Rims now and the sound is still there....

BUT...not at the same speed. 3 kph higher now

have to live with that "feature" i think ....