BBSHD rotational knocking sound when under power

Skizz

10 µW
Joined
Jun 15, 2020
Messages
5
*Previously posted in 'Technical' forum

Would be grateful for thoughts on an issue with a new BBSHD which has developed a rotational knocking noise under medium-to-high torque, occurring under both PAS and throttle.

Drive is a BBSHD with Lekkie BBSHD final drive cover V2, running at 52V and fitted to a Yuba Mundo Lux frameset.

Knock occurs around once per revolution but does occasionally vary in position and only happens under power; zeroing the PAS and grinding up some big climbs with leg-power only doesn't make it happen.

Linked vids show issue in motion and also the condition and engagement noise while stationary. Pulled the cover off today and discovered the outer thrust bearing-race was backwards but no visible damage. Final drive main bearing felt fine and final drive gear and pinion looked good so wiped everything down, re-greased (Aeroshell 22) and reassembled for test ride. All good for five miles until I pulled over to let a vehicle past and when pulling away again up a hill the knock started again. Excuse moderately bad language; couple of idiots decided to cut me up in one clip

[youtube]2VNdrLwiNiM[/youtube]
[youtube]GEkv4COi8Z0[/youtube]

Under throttle:
[youtube]YfqJefyVba0[/youtube]

Double knock:
[youtube]BAysIx73pHo[/youtube]

Double and single knock with PAS & throttle:
[youtube]JrQgeKZjkqk[/youtube]


Obvious stuff already checked is:

- Drive securely fitted and properly torqued with no free-play, pitching or rotation in BB shell
- Cranks torqued to spec with no play
- Pedals correctly installed with no freeplay or bearing issues
- New 42t Lekkie clone ring: tightened to spec torque
- New 9-spd chain and 11-42t cassette: correctly fitted, lockring torqued to spec and no play at cassette-to-freehub body interface
- Rear hub is Hope Pro 4 with steel freehub body with pawls and engagement ring in good condition and no play at freehub body to hub interface

First BBSHD I've worked on so thoughts greatly appreciated. Thanks
 
last time had sound like this was when had new chainring, cassette and chain (takes few miles wear in go quiet ) but I did not use the quick link for chain just used chain tool this resulted in one of the links being very tight and knocked when going round derailleur, did setup have noise from new or just appear , did you fit cassette yourself? check teeth not bent chainring , I had turn bike upsidedown and (motor off) turn pedals by hand to find where noise was coming from good luck :mrgreen:
 
I recently had a similar noise under load, once per revolution. Opened up the motor, the clutch had some damage, small metal pieces inside it. Replaced it with a new one, gave the gears a fast clean and new grease. No sound after that. I am just sharing my experience with a similar issue. :)
 
The issue was never fully diagnosed but thankfully I purchased through a good seller who swapped the drive without any argument. The replacement is problem-free. Someone else I know who's done a lot of work on BBS units professionally suggested something may be going on with the nylon transfer gear or have come adrift at the stator. Getting to that would've meant completely stripping the unit though and I wasn't willing to do that on a brand new drive. Either way, buying through a reliable seller saved me a lot of hassle.

Greendog said:
last time had sound like this was when had new chainring, cassette and chain (takes few miles wear in go quiet ) but I did not use the quick link for chain just used chain tool this resulted in one of the links being very tight and knocked when going round derailleur, did setup have noise from new or just appear , did you fit cassette yourself? check teeth not bent chainring , I had turn bike upsidedown and (motor off) turn pedals by hand to find where noise was coming from good luck :mrgreen:
Thanks for that and apologies for not responding sooner. Drivetrain was all brand new, in good condition and correctly fitted (I'm a bike mechanic but that doesn't mean I can't make mistakes). It was definitely the drive at fault and most likely something on the motor side, either the nylon gear or the stator. Either way, I wasn't about to completely strip a brand new motor and the seller agreed that wouldn't be reasonable so swapped it out for me.

jegerjeger said:
I recently had a similar noise under load, once per revolution. Opened up the motor, the clutch had some damage, small metal pieces inside it. Replaced it with a new one, gave the gears a fast clean and new grease. No sound after that. I am just sharing my experience with a similar issue. :)
Fair point, and while the clutch and bearings were all fine they're definitely near the top of the list for diagnosing mystery noises once you've ruled out the other usual suspects, i.e. drivetrain, hubs, cranks, pedals, BB, seatpost/saddle etc.
 
Don't mean to high jack a thread or anything but I'm also getting that exact noise after 3100km does anyone actually know what it could be?.
Cheers
 
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