BBS02 bottom bracket damage

[srh]

Hi,

I have run into a couple of issues with my BBS02 after ~4000 miles that I was hoping to get some help with. I think this all started because I didn't tighten the bolts on the crank arms enough in the first place. After a while the crank arms worked themselves loose, so I tightened the bolts every time I heard the bottom bracket squeaking, but they kept coming loose even though I torqued them to 40Nm after realizing they could work themselves loose (probably the squares were out of round at this point). Each time I tightened them they must have been getting pushed further and further onto the crank shafts and eventually the cranks were interfering with the bottom bracket part of the bbs02 so I had to throw them out and get some new ones. I didn't think too much of this until the new ones ended up interfering with the bottom bracket also after re-tightening a few times and also wouldn't stop squeaking (this time I torqued the bolts to 40Nm when first installing the crank arms), so I decided to have a closer at the bottom bracket. It seems like there is a lip on the bottom bracket that is pretty badly damaged (see photos).


After looking at a few videos/pics of dismantled BBS02s, it seems like this lip might be holding a 'cup' in place - with the bottom of the cup being inside the bottom bracket and providing the surface that the bearings push against when you tighten the crank shaft lock nuts as shown in this pic:


I haven't had a chance to take the whole thing apart yet because I'm using it get to work everyday. Does anyone know what is going on here? Is this a big problem? Can I replace that cup thing or am going to have to get a new unit?

I also guess I need to get a new crank shaft and cranks because I might have worn the tapers out on the shaft and arms (because my new crank arms can get pushed on too far also even though I was careful with the new set to torque the bolts to 40Nm from the start). Where is a good place to get a replacement crank shaft from? Who has the best selection of BBS02 replacement parts?

There is also one last problem (for now)! One of the M6 bolts that attaches the mounting plate to the motor seems like it might have been stripped... I tightened it until the spring washer was compressed, and tightened it a little bit more (not that much!) and suddenly it started turning fairly easily again, so I stopped trying to turn it, and assumed that it have been stripped.... Is it possible to just replace the BBS02 LHS outer case?

Thanks!

 

[fechter]

Wow, for that many issues, seems like it would be a lot less work to just get a new BBS02 motor. You could use the old one as a parts donor. 4,000 miles is not bad really.

Somebody was selling BBS02 parts, but can't remember off the top of my head who it was. Not sure if you could get those parts and what it would cost.

Next time use Loctite on the tapered square of the cranks.

 

[Lurkin]

^Agreed. But wheres the fun in that! I'd consider that distance premature for replacement, but too old to really be a warranty talking point with the original vendor.

The bolts that come with crank arms to hold them on already have loctite on them - just need to grease the crank spindle before installing and do it up sufficiently tight. It sounds like you have damaged your crank spindle or it was never the correct size to begin with - i.e. a manufacturing default. Unfortunately, unlikely you can go back to the vendor on this now that so much has happened in between. I would be looking to replace crank, crank arms, bearings etc and grease generously before reinstalling on to the bike. For the amount of work, and that you need to buy the crank anyway - replacement bearings and seals are cheap insurance.

Perhaps you could retap the mounting bolt to a larger size, struggling to remember what that area looked like or whether you could easily get a tap in there.

I'm under the impression you can get any part you want - just depends on who will sell it to you and whether they perfectly understand what you need. Going down this road will unlikely to be cheap or easy, and make sure you add a fair margin for any freight on new parts from China. The freight, rather than the part price, is usually the expensive part. Best bet is either em3ev or greenbikekit - but Fechter's advice is sound - I doubt it will be cheaper or more reliable than purchasing a new unit. Emails are cheap enough to send to find out the answer.... 8)

 

[srh]

Thanks for the input everyone. I agree, what is the fun in buying a new unit but I also agree that that is probably the smartest thing to do! Getting a new axle and installing it myself doesn't sound too bad; however, I'm more concerned about that chipped cup/lip - I have never seen such a replacement part or any mention of this in videos. If the remainder of the lip fails, then presumable there is nothing preventing the axle from moving to the right (until the left pedal interferes with the bottom bracket)??? Or is the cup some kind of press fit and will still hold with or without a lip... or is it not important at all because the surface inside the bottom bracket (that the bearings push against) is actually the same piece of metal as the whole bottom bracket 'cylinder'. Any input from someone who has taken one apart?

The crank spindle didn't show any signs of damage, so maybe I just got unlucky and got one with tapers that are slightly too small.

 

[Lurkin]

the most information in a thread about BBSx cranks, bearings, exploded diagrams etc - https://endless-sphere.com/forums/viewtopic.php?f=28&t=65711&hilit=bbs02+bearing

however, best method is to nip it apart and check. Bafang is notorious for making design changes/part changes without telling anyone....