2011 model year A2B Metro Gen. 2 strange vibration + noise.

[ebikefanusa]

Hi,

My 2011 A2B Metro Gen.2 has been doing a strange "buzzsaw" noise accompanied by a strong vibration on either throttle up or full throttle.

Watch and listen to the first minute or so of my video and see if you know what's going on:
http://youtu.be/ZrIpKv3DIKQ

I made a more recent video with more instances of this issue...listen especially to the 19:08 mark of the video:
http://youtu.be/7OPGdQ0Z1u4

The bike has been great for the first 950+ miles before this issue cropped up.

Not sure where the sound is coming from..sometimes it feels like the front wheel area or the bottom of the downtube area (controller) or the kickstand...or maybe the hub motor? But when I go on full throttle when the back of the bike is propped up on the kickstand, it doesn't occur so that could rule out motor? Maybe when sitting on bike something changes?

The issue comes and goes randomly and only happens when applying throttle which I thought should rule out any rotor or brake interference but then again maybe motor vibration transferred to a rotor could make that noise? Or something in the fork? I have no idea. Really stumped.

I've been living with it the past few months because the bike runs but I have exhausted troubleshooting ideas on this unsettling noise that happens from time to time in all my rides since July 2012. It's like either a metal on metal scraping noise or some spinning interference slicing/buzzsaw noise and I feel a noticeable vibration whe it happens...on full throttle while riding.

Anyone else experience this before or have a clue to what's going on???? Is it brake/rotor sound caused by motor vibration? Is it kickstand springs vibrating on throttle up? Os there something inside the controller area under teh main battery in teh downtube??? I am really stumped.

 

[amberwolf]

Sounds just like a disc rotor scraping to me. If there are no visible marks on the rotors, maybe check the motor wheel's axle nuts to be sure they are tight, and that it hasn't worked loose, allowing it to scrape rotor on pads or fork when accelerating.


Optionally, if it has disc front and rear, take the pads out of one brake and check again, then put htem back and try the other one if the first doesnt' eliminate it.

 

[dogman dan]

That doesn't sound like the familiar motor stutter to me, which is often caused by a poor contact at one or the other plugs to the motor.

I'd be looking at "bike problem" stuff. Things like a disk rotor misadjusted, a fender rubbing, or maybe even a bad bearing allowing a wheel to flop. Loose spokes could also allow a rim to wander under various riding forces.

I remember one perplexing one for me. I could tell something was rubbing a tire, but couldn't seem to find it. Later on, when the insulation and the wire was cut, I realized it was a wire to the motor rubbing. Thing was, it rubbed when I got on the bike. When I got off, the suspension went up, and the wire straightened so it looked perfect every time I got off to look.

So look at that kind of thing as well, maybe have somebody sit on the bike, then you look for anything rubbing.

 

[ebikefanusa]

I'll give these tips a try. Thanks!

 

[ebikefanusa]

Reinstalled front BB5 brake pads and so far so good. Did notice a little vibration but nothing as bad as the video where it makes a funny noise...at least not yet...will do more test rides this weekend to confirm. Might consider moving up to BB7 brakes. What size and rotor is recommended? Do I stay at 185mm like the stock rotors or go larger?

 

[edamame]

I use 200mm front rotors with 185mm rears with BB7 calipers on my A2B Metro. The brakes work well up to 38mph. I didn't much like the BB5 brakes.

 

[ebikefanusa]

Hmm..Seems like I still have the occasional buzz saw sound. Sounds like it's coming from the front fork area. Can't seem to figure out what is causing this.

Any other ideas welcome.

My Metro is still at factory stock 20 mph. Might upgrade to 185mm rotors and BB7s front and rear soon.

 

[recumbent]

Maybe it's the fender bracket buzzing from the knobby tires.

 

[ebikefanusa]

I should have posted the solution long time ago but thought I'd update in case anyone else runs into this "buzzsaw" noise issue. I finally discovered it was due to a loose kickstand hinge nut causing the tension springs in the kickstand to vibrate on motor throttle up. Once tightened the noise issue has all but disappeared. The only downside is my hinge hut is so tight the kickstand doesn't retract as smoothly on its own and I have to physically kick it up but that beats haivng an annoying noise when riding.