Bafang BBS02 Pedaling Vibration

[ThatDudeInAK]

Hey everyone! Before I go on asking questions, I'd like to say thanks to everyone on this forum. Lurking around has really helped me in my e-bike build!

Ok, I finished my build about 2 weeks ago and already have over 130 commute miles on it. Over the last two weeks I have been troubleshooting things here and there but there is one issue I can't seem to figure out.

When pedaling at higher speeds (20+ mph) I am getting a vibration that can be felt through the pedals. It seems to be more noticeable at higher speeds when I am in a higher gear. If I stop peddling and hammer the throttle the vibration is not there, so it seems to only be occurring under the force of me actually peddling.

I initially had issues securing the motor to the bottom bracket but I bought a bbs02 instillation wrench from lunacycle and re-installed the motor. During the re-install I ground down the bottom bracket a bit to insure the tooth plate had a clean and flat surface to bite into. I torqued down the lock nut as much as I could and I used blue threadlocker on it as well as the secondary locknut cap.

I just got done with a 29 mile commute and the motor didn't budge at all. But... I am still getting a vibration through the pedals when in a high gear going 20mph+. I have searched around and found several possible explanations but nothing conclusive. The two below being the most likely in my mind.


1. The chain is offset when in a high gear and causes vibrations at high speeds.
2. The drive shaft of the motor is moving vertically within the bottom bracket when applying force to the peddles.


Has anyone else experienced this? Is it considered "normal" or was there a way to fix it?

 

[flymeaway]

I ground down the bottom bracket a bit to insure the tooth plate had a clean and flat surface to bite into.

??? This one is a first. The bottom bracket from the manufacturer should have been OK.

1. The chain is offset when in a high gear and causes vibrations at high speeds.
2. The drive shaft of the motor is moving vertically within the bottom bracket when applying force to the peddles.

Concerning observation #1, everyone who has installed a mid-drive kit and uses a standard derailleur and rear cassette has the same set-up and I don't recall anyone complaining about vibration. Your 2nd observation describes the design of the drive itself which every installation has and if this were a design flaw then everyone would experience vibration.

You maybe experiencing the sensation (vibration) of what happens when you "over drive" (for lack of a better phrase) the system. You will experience some feed back via noise and what you refer to as "vibration" if you are pedaling at a very high cadence in a high gear. I say maybe, because I experience this situation when climbing very steep grades at high power settings with high pedaling cadence. The drive makes a buzzing sound and has a noticeable change in feel at the pedals. However, this is the only circumstance where this happens. At high speeds and normal riding, the drive is almost unnoticeable during operation except for the power output.

Hope that helps.

Court J.

 

[ThatDudeInAK]

??? This one is a first. The bottom bracket from the manufacturer should have been OK.

1. The chain is offset when in a high gear and causes vibrations at high speeds.
2. The drive shaft of the motor is moving vertically within the bottom bracket when applying force to the peddles.

Concerning observation #1, everyone who has installed a mid-drive kit and uses a standard derailleur and rear cassette has the same set-up and I don't recall anyone complaining about vibration. Your 2nd observation describes the design of the drive itself which every installation has and if this were a design flaw then everyone would experience vibration.

You maybe experiencing the sensation (vibration) of what happens when you "over drive" (for lack of a better phrase) the system. You will experience some feed back via noise and what you refer to as "vibration" if you are pedaling at a very high cadence in a high gear. I say maybe, because I experience this situation when climbing very steep grades at high power settings with high pedaling cadence. The drive makes a buzzing sound and has a noticeable change in feel at the pedals. However, this is the only circumstance where this happens. At high speeds and normal riding, the drive is almost unnoticeable during operation except for the power output.

Hope that helps.

Court J.

Thanks for the feedback. After a little more research I have found multiple cases of this vibration and one of the explanations points to this happening when the controller hits the amperage cutoff for any given PAS level, resulting in a slight vibration through the pedals.

I did some more tests this morning on my 14 mile ride into work and I believe it is coming from the controller.

The vibration starts at a different cadence with each PAS level. On flat ground, I was getting the vibration going about 23mph in high gear at PAS 7 and when I bumped it up to PAS 9 it went away until about 28mph.

Also, I ground the BB down because I had the motor shift on me when I first installed it. It wasn't tight enough and the tooth plate ended up ripping up the BB a bit. It's now been 45 miles from the re-install and it hasn't budged so I am happy with that.