Motor "kick-back" when stop pedaling

[dborosev]

I took a Verve with Active Line motor out for a test spin. I noticed that when I stopped pedaling, the motor sort of gave a kick in reverse pedal direction. So my feet would bounce back in reverse slightly as soon as I stopped.
The sales guys said this was normal, but I've ridden shimano steps before, and never felt this at all.

 

[McCorby]

My girlfriend’s 2019 Verve + with the standard Active Line does not do this. Is this a newer Verve with the Active Line Plus motor? Even if so, I wouldn’t think this is normal. Did they have another Verve you could try?

 

[Deacon Blues]

I have a gen 4 motor on my Cannondale Topstone Neo Lefty 3 and mine doesn't do what you describled.

 

[William - Bosch Team]

Hello!

What you are experiencing is normal.

The Gen3 Drive Units have a different design than the Gen4 Drive Units. Gen4 has a ratchet mechanism that allows free, forward motion of the chain ring even when the cranks are not moving. This is similar to Gen2 Drive Units. Gen3 uses a one-way bearing between motor gearing and output, but the chainring mount and crank spindle are essentially attached to each other (no ratchet mech.) The chainring mount and the crank spindle interface with each other via splined surfaces, designed for just a tiny amount of "play" or "give." This is where Gen3 measures rider's torque input.

Due to this design, if you stop pedaling abruptly, you will feel a slight clunk. The amount of clunk you feel varies depending on individual rider's pedaling behavior- Some riders stop pedaling very abruptly and tend to "lock" their leg with a pedal down in the "6:00 position," other riders do more of a "soft stop," and let the pedaling sort of spin out over the course however many degrees of rotation.

I hope this helps!

 

[dborosev]

Thanks. So the Gen 4 motor would not do this?
Is the gen 4 synonymous with the "Active line plus"?

 

[William - Bosch Team]

Thanks. So the Gen 4 motor would not do this?
Is the gen 4 synonymous with the "Active line plus"?

You are correct. Gen4 drive units do not have the small "clunk" feeling when you stop pedaling abruptly. This is because the mechanism that transmits power from the motor to the output shaft in the Gen4 DU design involves a ratchet mechanism that allows the chain ring to move forward without any effect on the crank spindle.

Active Line and Active Line Plus are built on the Gen3 drive unit platform.

Gen4 drive units are:
- Performance Line CX
- Performance Line Speed
- Cargo Line
- Cargo Line Speed

 

[PedalUma]

Hello!

What you are experiencing is normal.

The Gen3 Drive Units have a different design than the Gen4 Drive Units. Gen4 has a ratchet mechanism that allows free, forward motion of the chain ring even when the cranks are not moving. This is similar to Gen2 Drive Units. Gen3 uses a one-way bearing between motor gearing and output, but the chainring mount and crank spindle are essentially attached to each other (no ratchet mech.) The chainring mount and the crank spindle interface with each other via splined surfaces, designed for just a tiny amount of "play" or "give." This is where Gen3 measures rider's torque input.

Due to this design, if you stop pedaling abruptly, you will feel a slight clunk. The amount of clunk you feel varies depending on individual rider's pedaling behavior- Some riders stop pedaling very abruptly and tend to "lock" their leg with a pedal down in the "6:00 position," other riders do more of a "soft stop," and let the pedaling sort of spin out over the course however many degrees of rotation.

I hope this helps!

There is momentum to the drivetrain. Pushing hard and then abruptly coasting (BMX style) will feed lingering inertia to the torque sensor. This is also common in TSDZ2 motors but only those with coaster brakes. You just need to learn to ride by easing off on pedal pressure slightly before coasting. By your second ride it will be second nature.