Hub Motor Making Grinding Sound When Rolling Bike - Power Off

CoffeeandBikes

CoffeeandBikes

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I went for a ride today on my fat tire dual motor bike. On the way home I heard something like a low grinding or rubbing noise when I pedal hard. I thought it was a fender rubbing, but it's not. Once home I turned off the bike and rolled it into my shop. With power off the rear hub motor makes a strange sound when rolling the bike forward or backward. With power on I can lift the rear wheel, crank the throttle and the motor works well without making that noise. When I let off the throttle the wheel freely spins without making the noise. The noise only happens when I'm manually rolling the bike while not under load, or if I pedal. Does anyone know what this could be?
 
CoffeeandBikes said:
I went for a ride today on my fat tire dual motor bike. On the way home I heard something like a low grinding or rubbing noise when I pedal hard. I thought it was a fender rubbing, but it's not. Once home I turned off the bike and rolled it into my shop. With power off the rear hub motor makes a strange sound when rolling the bike forward or backward. With power on I can lift the rear wheel, crank the throttle and the motor works well without making that noise. When I let off the throttle the wheel freely spins without making the noise. The noise only happens when I'm manually rolling the bike while not under load, or if I pedal. Does anyone know what this could be?
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I got a front hub motor that is doing this. It has been this way for a while. I refuse to disassemble it while the weather is nice to find out what it is.

I suspect it is wheel bearing play, which is letting the motor halves slightly make contact.

Winter is coming, soo I'll be tearing it down soon to find out.
 
It may need greasing. Then again could be loose magnets. But in all reality it's probably just the sound of the gears going around. It should be freewheeling going forward and dragging against the motor a little going backward. If you're getting the same sound going both directions without power and it's not a crunching type sound like the gears eating themselves then the bearing for the one way drive may be gone or going. Mine makes a very little gear turning noise (whining whirring) from both motors when I push it backward. Some gears make more noise than others especially if they are metal or metal clad... Nylon gears only make a little whining whirring noise when pushed backwards.
 
CoffeeandBikes said:
I went for a ride today on my fat tire dual motor bike. On the way home I heard something like a low grinding or rubbing noise when I pedal hard. I thought it was a fender rubbing, but it's not. Once home I turned off the bike and rolled it into my shop. With power off the rear hub motor makes a strange sound when rolling the bike forward or backward. With power on I can lift the rear wheel, crank the throttle and the motor works well without making that noise. When I let off the throttle the wheel freely spins without making the noise. The noise only happens when I'm manually rolling the bike while not under load, or if I pedal. Does anyone know what this could be?
Click to expand...
Sounds like something in your freewheel might have broken. Do you have a chain whip so you could take it off and have a look at it?
 
Annieolnie said:
Sounds like something in your freewheel might have broken. Do you have a chain whip so you could take it off and have a look at it?
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No, I don't have one. I had never heard of one until you mentioned it. I think that is the problem. As @BiggKidd was saying the bike should freewheel going forward. It is not and hasn't been for a long time. I only have around 500 miles on the bike. I noticed that it wasn't freewheeling pushing forward a long time ago. I couldn't remember if it did that when I first got it, but I don't think it did. What is the solution to this and is it really a bad thing?
 
BiggKidd said:
It may need greasing. Then again could be loose magnets. But in all reality it's probably just the sound of the gears going around. It should be freewheeling going forward and dragging against the motor a little going backward. If you're getting the same sound going both directions without power and it's not a crunching type sound like the gears eating themselves then the bearing for the one way drive may be gone or going. Mine makes a very little gear turning noise (whining whirring) from both motors when I push it backward. Some gears make more noise than others especially if they are metal or metal clad... Nylon gears only make a little whining whirring noise when pushed backwards.
Click to expand...
It does not freewheel when pushing forward and hasn't for a long time. I couldn't remember if it didn't do that when new. I thought it odd.
 
Oh, heck no. If it's not your motor you can just unscrew your freewheel and screw on a new one. You even get to pick what size gears you want. The chain whip just holds the gears while you use an insert tool to spin the gearset off. None of it is expensive.
 
I don't know your bike so double check which insert you need but even the cheap chain whips work fine.
Screenshot_20250914-131341_Chrome.jpg
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CoffeeandBikes said:
It does not freewheel when pushing forward and hasn't for a long time. I couldn't remember if it didn't do that when new. I thought it odd.
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Just to make sure we are all on the same page. I'm talking about the one way bearing that lets the gears go round inside the motor not the freewheel for the chain. You see the gear set should be "free wheeling" not dragging the motor along when pushed forward but it SHOULD drag the motor along when pushed backward. Again it may just need greasing / lubricating.

Far as the chain's free wheel I've seen them stopped with a piece of grit smaller than a BB so I'd try cleaning it first if you think it may be part of the problem. To me it sounds like what your describing is the bearing on the gear plate inside the motor...
 
Could also be a bad bottom bracket. Move the cranks sideways to see if they have play. No play doesn't mean they are good, however. With the chain removed you may be able to ID which component is making the noise.
 
BiggKidd said:
Just to make sure we are all on the same page. I'm talking about the one way bearing that lets the gears go round inside the motor not the freewheel for the chain. You see the gear set should be "free wheeling" not dragging the motor along when pushed forward but it SHOULD drag the motor along when pushed backward. Again it may just need greasing / lubricating.

Far as the chain's free wheel I've seen them stopped with a piece of grit smaller than a BB so I'd try cleaning it first if you think it may be part of the problem. To me it sounds like what your describing is the bearing on the gear plate inside the motor...
Click to expand...
I would think a bearing noise would be constant. I've broken cassettes on midrives which of course, don't have any rear internal motor, and when a pawl hangs up or breaks you get the sound that C and B is describing. If he takes it off and fiddles with it, he should soon know.
 
BiggKidd said:
Just to make sure we are all on the same page. I'm talking about the one way bearing that lets the gears go round inside the motor not the freewheel for the chain. You see the gear set should be "free wheeling" not dragging the motor along when pushed forward but it SHOULD drag the motor along when pushed backward. Again it may just need greasing / lubricating.

Far as the chain's free wheel I've seen them stopped with a piece of grit smaller than a BB so I'd try cleaning it first if you think it may be part of the problem. To me it sounds like what your describing is the bearing on the gear plate inside the motor...
Click to expand...
I can hear the motor gears turning when pushing the bike forward.
 
BiggKidd said:
It should roll free when pushing forward and or coasting. If the gears are turning something inside isn't right unless you're geared hub motors are made different than the ones I am used to.
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That's what I don't know. The rear hub motor gears have turned when manually rolling for a long time. I "think" it didn't do that when it was brand new, but I can't be sure. The front hub motor doesn't seem to do that, at least not that I hear.
 
UPDATE: I believe the problem is solved, and I feel very silly. I had read that the fender rubbing could be the problem. I had tested the wheel in the air with no rubbing so thought it not to be an issue. I took the bike out into the sunshine so I could clearly see the clearance of the fender. I saw a BIG PROBLEM. The bolt that holds the rear rack and the rear fender on the right (cassette) side was MISSING. This had caused the rack bracket to have free play and slightly interact with the outside of the cassette. The holes on the bike are tapped directly into the aluminum frame. It looks like the threads stripped. I trimmed down a slightly longer and slightly larger bolt and ratcheted it through the existing hole - hopefully creating decent enough threads. I locked it down tight with both flat and locking washers. After I was done the bike rolled smoothly forward without dragging the rear hub motor. I still haven't ridden it yet as it's getting a bit late. I just wanted to update this. If I still experience problems, I'll update. BIG THANK YOU to everyone!!!
 
If the bike is newish and lowish miles, it could just be that the factory grease has migrated away from the gear mesh somewhat. If so, it's no big deal unless they didn't put enough grease in it to keep the gear engagement surfaces lubed.
 

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