Pedalling e-bike when motor turned off

[Zimmerframe]

Hard to pedal easily.

Have you taken the chain off ?

Bike in the air - on a stand, strap, whatever works for you.

Then check the wheel .

Then check the pedals/motor- there should be pretty much zero resistance everywhere.

"Drag" is generally just tyres/weight and the difference between assisted and unassisted.

 

[irie]

Have you taken the chain off ?

Bike in the air - on a stand, strap, whatever works for you.

Then check the wheel .

Then check the pedals/motor- there should be pretty much zero resistance everywhere.

"Drag" is generally just tyres/weight and the difference between assisted and unassisted.

And increased wind resistance.

 

[Zimmerframe]

And increased wind resistance.

Depends on your underwear.,

 

[Tetley]

Further to above advice, take the chain off the front ring, balance the bike against a wall, sit on it and pedal. There might be a very tiny bit of resistance compared to a standard clockwork bike, but nothing that saps any effort. All you are turning is the 2 crank bearings, and slipping the motor sprag bearing. (The pedal shaft is locked to the crank shaft by its sprag bearing, and ALL the motor / belt / gears components are disconnected).
If it's not tuning freely, the unit is knackered.

 

[jroberts]

Further to above advice, take the chain off the front ring, balance the bike against a wall, sit on it and pedal. There might be a very tiny bit of resistance compared to a standard clockwork bike, but nothing that saps any effort. All you are turning is the 2 crank bearings, and slipping the motor sprag bearing. (The pedal shaft is locked to the crank shaft by its sprag bearing, and ALL the motor / belt / gears components are disconnected).
If it's not tuning freely, the unit is knackered.

Thanks. I did that, it is not running freely. Did not seem as bad as my recent ride, where even at low speed on a flat I had to stand up to get it to move. Off to the shop, again.

 

[irie]

... even at low speed on a flat I had to stand up to get it to move ...

 

[Tetley]

Thanks. I did that, it is not running freely. Did not seem as bad as my recent ride, where even at low speed on a flat I had to stand up to get it to move. Off to the shop, again.

Either the crank bearings are seized, or the motor sprag bearing has seized and isn't disengaging the belt, gears and motor.
If you turn the chain wheel backwards (with the chain off and battery disconnected) you will find out what the drag of the belt, gears and motor feels like, which is significant, and would sap around 20% of riding power with the motor switched off. if it's the same drag as pedalling forwards, the motor sprag is seized, and a new motor, or rebuild is needed.

 

[Mikerb]

I agree that if there is considerable drag then the sprag bearing is not releasing. There is one other possibility and that is that OFF does not in fact switch the motor off. Removing/disconnecting the battery would discount that as a possibility.

 

[Tetley]

Yes, but the drag from the fat low pressure triple compound high grip tyres does! Otherwise I'd be going even faster!

I agree that if there is considerable drag then the sprag bearing is not releasing. There is one other possibility and that is that OFF does not in fact switch the motor off. Removing/disconnecting the battery would discount that as a possibility.

On a Levo, 'off' on the TCU is completely off, ie motor not turning. Even if the motor was slightly turning, it would make no difference to drag because of the sprag bearing.
The motor is completely disconnected from the drive until it's spinning fast enough to catch up with the sprag bearing where it then starts to assist. If the motor drops in speed, it disconnects again. It works exactly like the freewheel hub on the rear end, if you stop pedalling, the rear wheel disconnects from the pedals, with no drag. You then have to pedal fast enough to catch up with the freewheel, so as to start drive again.
A working sprag bearing will never allow the pedals to turn the motor, not even slightly. If it's seized, then yes it can.

 

[rzr]

i don't remember if I posted it here (before anyone asks - of course motor is OFF)

 

[Turbo vado]

Hi folks
I am quite new to e-biking. When the motor is 'assistance off' it feels like I am pedalling through glue - feels like massive resistance. Is this 'psychological' after the feeling with 'assistance on'. I have a new Specialized turbo levo so I thought there was a clutch that disengaged the motor when off - so why does this feel so 'heavy'?

dps21 Don’t worry, your not imagining things, l know exactly what you mean, my Vado is the same, 100% sure the issue is not mechanically related, seems to me that the motor retains some electro magnetism when switched to the “off” and l feel this is what we are experiencing which makes it feel like peddling through treacle.

 

[Turbo vado]

Hi folks
I am quite new to e-biking. When the motor is 'assistance off' it feels like I am pedalling through glue - feels like massive resistance. Is this 'psychological' after the feeling with 'assistance on'. I have a new Specialized turbo levo so I thought there was a clutch that disengaged the motor when off - so why does this feel so 'heavy'?

Read through the post, you got some well amusing comments and opinions. I am going to contact Specialized but in the meantime as a work around l am setting the assistance in tuning to 5% and see how this effects things.

 

[Tetley]

dps21 Don’t worry, your not imagining things, l know exactly what you mean, my Vado is the same, 100% sure the issue is not mechanically related, seems to me that the motor retains some electro magnetism when switched to the “off” and l feel this is what we are experiencing which makes it feel like peddling through treacle.

If Your Vado is experiencing drag then-
a. The motor is faulty , and the sprag bearing is not disengaging properly.
b. There is something else in the drivetrain or brakes that's dragging.
c. You are imagining it due to coming off assistance really does fee like riding in treacle to start with.

"100% sure the issue is not mechanically related, seems to me that the motor retains some electro magnetism when switched to the “off” "

100% sure the motor is completely off and completely disengaged from the drivetrain when off. There is no 'retained electromagnetism' If you look up how these motors work, particularly how sprag bearings work, you will understand that a properly working Brose motor only gives a very tiny amount of almost undetectable drag when switched off, and the entire motor, gears and belt are completely disconnected, and do not turn, not even slightly.

As said above, take the chain off the ring and turn the pedals. If it easily turns with one finger, it's fine, if any significant resistance is felt, the motor is faulty. If you pedal it with your feet, with the chain off, it should feel completely free.

Watch this video of a Brose motor rebuild, and you will see how these motors are constructed, how they work, and how they fail. What I'm saying might make more sense!