Clicking noise rear wheel problem bafang - diagnosing?

[nukezero]

So I put about 120 miles now on my Motiv 48V bike 26" which comes with a Bafang BPM 48V 500 watt motor. Just today, I noticed during my commute there seems to be a clicking metallic noise, almost like a spoke is hitting something. It isn't consistent like when it goes in a circle and hits it. It's intermittently consistent. It's also more frequent when going faster.

So here's what I noticed:

1. If I stop the bike and spin the rear wheel by hand, I don't hear the clicking noise.
2. If I lift the rear wheel up and apply throttle full speed, half, and partial, I don't hear the clicking noise.
3. If I sit on it and ride around with the throttle at low speed, I can hear it.
4. If I don't use motor power, and pedal like a normal bicycle, I can also hear it.

So it seems like I can only get the noise to come out if I on the bike applying some load to the motor and wheel.

So what could be the problem? Is it a stripped internal planetary gear? I also heard it could be a loose spoke? I just got the bike 2 weeks ago so I never did any tune up.

 

[fechter]

I'd guess a bearing, but it's hard to tell without taking things apart.
Loose spokes can do it, that's easy to check.

 

[Gregory]

Yep I'd start by checking the spokes.

Greg

 

[d8veh]

Spokes. You get this on most Chinese kits. I think that they expect you to adjust the spokes before using he kit.

 

[nukezero]

Spokes. You get this on most Chinese kits. I think that they expect you to adjust the spokes before using he kit.

I'm also convinced it's the spokes. It sounds like a metal is hitting something but that metal has an echo effect. My spokes are crossed so when I sort of fling them, it makes that metallic noise and that echo effect when they rub. I do notice that one of the spokes is a bit looser in tension than all the rest. I'm wondering if I could just take a wrench and tightening it up a bit with a few turns?

I did hit a minor manhole doing 30mph downhill and it jolted the bike. Wondering if that caused that spoke to get out of whack. Bike rides fun otherwise, no vibration.

 

[bowlofsalad]

Spoke tension is an extremely important detail for a wheel. Do not go for another ride until you are sure you've got the spokes at appropriate tension. A loose spoke will be damaged.

The vagueness of 'take a wrench and turn it a few times' suggests to me that you don't know much about wheel building. You could end up breaking the spoke or the rim if you just do this willy nilly.

There are several options for determining spoke tension, some of them are a bit trickier than others. An experienced wheel builder will know just by squeezing or wiggling the spoke, and maybe by plucking it and listening to the frequency. Others might rely on tools such as a spoke tension meter, there are also programs that people use to determine spoke tension as well based via a microphone. The primary issue with you doing this yourself is, even if you have some vague understanding of tension, it would be pretty easy to make the wheel very untrue.

My advice is to spend some time reading on the subject. http://sheldonbrown.com/wheelbuild.html Or, to take the wheel to someone who knows how to true and build a wheel. If you want to be really progressive, you might consider relacing the wheel with quality spokes (and maybe a new rim depending on the rim). The word on the forum is the spokes that come with ebike hubs are trash. You've likely already abused the spokes, it may just be a matter of time until you start breaking them while riding. I'd much rather rebuild a wheel at my leisure than have to walk, drag, or drive the bike back home because of a broken rim or spoke. This advice really operates within the ideas of reliability over other concepts such as cost. If you don't really care all that much if you break a spoke or whatever, you could probably try and just dive into tensioning the spokes yourself and hope for the best. But if it were me, I'd get new quality spokes and rim and either relace or have someone relace for me.

 

[nukezero]

It seems that the noise is getting a bit worse. The spokes all seem fine. I will have my LBS check it out tomorrow. This bike is not a kit, it is a Motiv 48V bike. It looks like this in the picture. It has a Bafang motor and 12G spokes.

I still can't get the noise to produce when I lift the rear wheel up and spin the rear tire by hand, crank the pedal by hand, or spin the wheel by throttle. It can only come out after I sit on the bike. I also notice that it is revolution consistent meaning, the noise occurs at the exact revolution/turn of the wheel. I wonder if it is possible to be the freewheel bearing? If so, that would be great as I'm planning to replace the freewheel with 11T DNP.

 

[Shylo]

What was the final outcome of your hub clicking noise? I just purchased a "new" (in the box) 2018 ebike and I'm getting the exact same clicking noise as you've described. Because I purchased the bike at an Auction in Feb 2020, the Manufacturer is refusing to service it or sell me parts because the Auction House was not an Authorized Dealer.

 

[amberwolf]

Have you checked your spokes?

As noted above, they are the common thing between riding with and without power causing the noise, but not having the noise when offground with or without power.

It's common with the machine-built wheels (which this probably has) to not be tensioned/trued, just assembled. So you may have to tension the spokes yourself. (A dealer may or may not do this when they "build" the bike out of the box; depends on if they feel like charging extra for a "tune up").

Also, it's common for them to use spokes that are too thick for the rims, so they can't hold the tension correctly. So when the wheel is stressed (under load, not in the air) the rim flexes becuase it's insufficiently compressed, and the spokes/nipples make sounds that resonate in the wheel (rim and/or hub) as they lose and gain tension.

If you tighten up the spoke nipples enough to have correct tension, they may stay fixed, but it is common that they don't because the rim cracks radially around the spoke holes (you may not be able to see the cracks, but sometimes they're obvious) and releases the tension on the spokes again.

The way to fix that is to replace the rim and use new spokes that are the correct size for that rim, usually 14g or smaller for bicycle rims, but you can get away with 13/14g single or doublebutted spokes depending on the distance from the hub flanges to the rim. Sometimes the hub's flanges on motors have holes so large you also have to use spoke washers so the heads don't pull thru.

Hopefully yours doesn't have damage to the rim, or get any...but you should try tightening up the spokes and retruing the wheel to see if it fixes the noise. Or have a bike shop do it, if you prefer.