eMTB BBS02 questions and concerns

[takiboris]

Recently I did my first "build" on a mountain bike I got for free, very green to this whole ordeal. Specs and questions/concerns are as follows (did a lot of ADHD searching but no solid answers on the specific things I'd like to know)

Bicycle: K2 Zed 4.4 Reflex, not too sure on specs since there's not much information on the internet for K2 in general and I couldn't find much on this specific model. 8 speed rear cassette with integrated shifter
Motor: Bafang BBS02 52t from LunaCycle with DPC-07 display
Battery: Hailong style 52V 20Ah 30A battery from Walmart (mounted on top in front of seat)
Brakes: Front JFOYH 4-piston hydraulic 160mm from Amazon, Rear is still stock cable caliper style.

MOTOR QUESTIONS AND CONCERNS
The chain keeps coming off from bumps, I've read that its more than likely chain alignment and can be fixed with guides, but can that also be remedied with getting a smaller chainring? Like going from a 52t to maybe 42t or smaller?

Is there any way to get multiple center chainrings like how the bike had before the conversion? Never seen a 24 speed BBSxx but still wondering if its possible even theoretically.

I've seen many posts on ES and other blogs on external controllers for the BBSHD but is it possible to mate a BBSHD controller onto a BBS02? Or even an external controller to get 30A on a BBS02 like a phaserunner?

I'm trying to get the most of this BBS02, without upgrading to a BBSHD or bigger for budget reasons. Breaking it is no problem however, got that car tinkering personality where if it breaks, its getting upgraded. Just wanna know if any of these things can be done, either if its been done or if its possible in theory.

Thanks in advance!

 

[amberwolf]

I thought there was a thread where someone had done a BBS02 with a PR, but all I could find were threads asking if it *could* be done (or had been). :/

However, essentially the system is the same, so you could use "any" controller (externally) to run the BBS02 that can deal with whatever position sensors the BBS02 motor itself has. With the PR, you would have to tune it to the BBS02 motor, but you may be able to use the BBSHD PR configuration as a starting reference.

Since the BBS02 doesnt' have a torque sensor or really anything unusual in the way of sensors in it that have to be adapted to, it shouldn't be too tough to get a controller working with it--it might need to support a high ERPM (the PR does, so do most controllers that handle high-ratio geared hubmotors, or fast RC motors (like VESC can), etc)


The PRv6 also supports several display types, so you can check it's manual or the grin site to see if it would support using the existing BBS02 LCD / buttons to control assist modes/etc without using a Cycle Analyst.

 

[Chalo]

The chain keeps coming off from bumps, I've read that its more than likely chain alignment and can be fixed with guides, but can that also be remedied with getting a smaller chainring? Like going from a 52t to maybe 42t or smaller?

If you're riding off road, you have zero business using a 52t chainring. Yes, using a 42t will help, because you won't have to be as far inboard on the rear sprockets to get a given ratio. Don't go lower than that, because smaller than 42t chainrings mount farther outboard and will make your bad chainline worse.

One thing you can do, that I did, is to select your most useful 6 cassette sprockets out of 8 and put them in the 6 outermost positions. Put the other two in the innermost positions and then use the derailleur low limit screw to lock them out. That way, your most troublesome, worst chainline gears aren't accessible anymore.

Is there any way to get multiple center chainrings like how the bike had before the conversion?

No. The motor and gearbox occupy the space that contained the middle and inner chainrings before the conversion. So... no.

 

[2old]

A Lekkie chainring (42t) and or crank arms will reduce/prevent chain loss since they provide a straighter chainline. I'm using 11-17-28, spaced 8-speed and don't have any problems off road in pretty severe terrain on a hardtail of FS bike.

 

[docw009]

Someone posted here that a BBSHD controller fits in a BBS02B, but a lot of people don't believe.

Can I replace my BBS02 motor core / rotor with a BBSHD?

It works! Bull. Doubting 'tom' huh? :lol: That's good. Calling out questionable information in forums is important. We'll see if any proof gets shared with us. It can’t be proven. The poster was last seen, “Last active:Oct 21 2022 10:12pm”, yet nothing…

endless-sphere.com

Chain might be too long or tension loose if it falls off.