My work's office is moving about 1.5 miles further away (and 400 ft further up a hill) than where it is now. I commute on a Specialized road bike, but I know that I won't ride as much after the move given the extra time/effort that will be involved. So (goaded on by a couple of bike-centric coworkers) I decided it was time to try building an eBike. After doing a fair bit of research online, I settled on the mid drive BBS02, and I bought a new 29er (Diamondback Overdrive) for $400 from Nashbar as my mod platform. My intention is to use this primarily (exclusively?) as a road/commuter, so I looked for a frame with a hard tail and a fork that could be mostly locked out. I put some narrow (35mm) commuter tires on it and road it around a bit - seemed OK.

I got a BBS02 "kit" from Luna. I put "kit" in quotes because - frankly - it really wasn't (see below), but it was a good deal on the parts I did end up with.
The conversion went fairly well other than few minor issues.
Issue #1) My bottom bracket is 73mm but the BBS02 comes designed for a 68mm BB. That meant the locking ring (red arrow in the picture below fit, but the outer locking ring/cover (yellow arrow in the picture below) didn't. My work around for the black ring was to turn it around and screw it on backwards (as shown). The gray ring holds the BBS02 in place (and preloads it against the BB) and the black ring holds the gray ring in place by jamming into it. Without the black ring, the gray ring will work itself loose - so you need *something* there. (Or locktite on the gray ring).
I can't get the tool on the spline to really crank it down tight, but I used some channel lock pliers to give it a bit of a turn. When I have time, I'll probably take the ring off, and machine off the lip enough it'll go on correctly. A second gray lock ring (part of the $6 "spare parts kit" at Luna) would probably work as a second lock/jam ring.

The other problem with the 73 mm BB is the gap between the mounting plate and the BBS02 of 5mm. In the picture above you can see the 5 washers at the blue arrow (1/4" washers, filed to flatten one side so they'd fit) I had to insert. I did this in two places. I also needed longer screws to reach across the gap. (I believe these were M6 screws). When I got to this point in the build I had to stop, and run to a hardware store to buy <$2 worth of washers and screws. This is one place where I say "this really isn't a 'kit' - or the necessary parts would be there..."
Once I got my extra hardware, and I jerry rigged the black lock ring on, I had no more issues installing the main hardware...
However, there were electrical issues:
Issue #2) I bought a carbon shark battery as part of the "kit". When I went to connect it to the BBS02 I discovered I had bare wires and needed to buy some sort of connector to hook on the battery to the motor. Another interminable delay while I searched for a $1 plug. Ultimately I bought a 5 pack from LunaCycle for $5 even though I only needed one (pretty annoying, right?). I got them soldered up and finally the bike was running.
Issue #3) I had bought a gear shift sensor, but the cable from it to the motor was too short (about 8" too short) - so I needed to buy an extension. Unfortunately, the extensions are only 1m long (~40 inches), so way more than I needed, but once i got it I just looped up the excess cable to try it out. At some point in the future, I'll probably cut and splice the line so the sensor has the "right length" cable on it, and I'll have a somewhat shorter extension left over (or two ends that are waiting for other purposes). Not a big deal, but be aware the gear sensor has a pretty short cable.

Issue #4) I would have bought the factory hydraulic brake levers with the eBrake cutoff capability, but they were out of stock when I ordered. I see today they aren't even listed any more. Instead I got the magnetic (hall effect) switches that come with a couple small but powerful magnets. The issue is I can't figure a good place to mount them on the brake levers that came on the bike - so I left them off. By and large this hasn't been a problem riding (since I'm commuting). Stopping pedaling causes the pedal-assist to cut out (with a bit of lag) - and it's not been a riding hazard for me so far. I may revisit this issue to see about some way to fashion a mount (maybe 3D print?) for the magnets. If you're riding off road (trail riding) I suspect that you're going to want to be sure these are installed.
By and large that's it - I put it together and it rides great. Let me describe some options I took and what I think about them now:
Since I am aiming to commute, I built the bike for speed (not power/torque for hill climbing), and I went with the largest chain ring (52T) I could. Even at that, I still mostly live in the smallest 4 or 5 cogs in the cassette. I'm glad I didn't go smaller than the 52T. The middle of the cassette lines up well with the chain ring (a bit hard to see here)

I have the c965 computer - doesn't seem to be an option at Luna any more, but I am happy with it. Might have opted for the full color display, but $45 seemed like too much of an upcharge.
The crank arms that come with the BBS02 are 170mm. After riding a bit, it felt "small" to me, so I swapped back on the 175mm's that came on the stock bike. I had to unscrew the chain rings from the right side (still have the 4 arm spider) and this feels better. I couldn't find a right hand side 175mm arm with the square taper hole, so I either need to live with the spider, or perhaps machine/grind it off. Maybe you could just get another left arm - and then use two left pedals, presuming you don't want clipless or something else that's "oriented" R vs. L...

As noted in other posts/blogs, the BBS02 Pedal Assist takes a bit of getting used to, but it's not that bad. Think of it as "cruise control" - in PA-Level1 the bike wants to go ~15 mph - no matter how hard you pedal. If you're going less than 15 mph the motor kicks in to help. If you're going 15 mph or more, there no motor assist. PA-Level2 = 18 mph, PA-Level3 = 21 mph, etc. The exact speeds for each level do seem to be impacted by what you set as the top speed for the motor. As you increase the top end speed, the various levels seem to spread out (and increase) a bit.
It also seems like if you exceed the "PA-Level" speed that the motor is working against you. In other posts I've seen people speculate that you're actually back driving the motor (or some portion of the gearing / clutch). That seems very likely to be the case based on how it feels to pedal.
In the end this was a fun build and an even more fun ride. However the frustrations that came with Luna leaving out $3 of parts needed to actually be “a kit†(when I paid $1100 for the kit), were really unnecessary. If you’re buying your parts from Luna, you probably want to go get the aforementioned items (2 longer screws, washers, and some connector – I used XT-60), or you’ll be cursing them as well…
I got a BBS02 "kit" from Luna. I put "kit" in quotes because - frankly - it really wasn't (see below), but it was a good deal on the parts I did end up with.
The conversion went fairly well other than few minor issues.
Issue #1) My bottom bracket is 73mm but the BBS02 comes designed for a 68mm BB. That meant the locking ring (red arrow in the picture below fit, but the outer locking ring/cover (yellow arrow in the picture below) didn't. My work around for the black ring was to turn it around and screw it on backwards (as shown). The gray ring holds the BBS02 in place (and preloads it against the BB) and the black ring holds the gray ring in place by jamming into it. Without the black ring, the gray ring will work itself loose - so you need *something* there. (Or locktite on the gray ring).
I can't get the tool on the spline to really crank it down tight, but I used some channel lock pliers to give it a bit of a turn. When I have time, I'll probably take the ring off, and machine off the lip enough it'll go on correctly. A second gray lock ring (part of the $6 "spare parts kit" at Luna) would probably work as a second lock/jam ring.
The other problem with the 73 mm BB is the gap between the mounting plate and the BBS02 of 5mm. In the picture above you can see the 5 washers at the blue arrow (1/4" washers, filed to flatten one side so they'd fit) I had to insert. I did this in two places. I also needed longer screws to reach across the gap. (I believe these were M6 screws). When I got to this point in the build I had to stop, and run to a hardware store to buy <$2 worth of washers and screws. This is one place where I say "this really isn't a 'kit' - or the necessary parts would be there..."
Once I got my extra hardware, and I jerry rigged the black lock ring on, I had no more issues installing the main hardware...
However, there were electrical issues:
Issue #2) I bought a carbon shark battery as part of the "kit". When I went to connect it to the BBS02 I discovered I had bare wires and needed to buy some sort of connector to hook on the battery to the motor. Another interminable delay while I searched for a $1 plug. Ultimately I bought a 5 pack from LunaCycle for $5 even though I only needed one (pretty annoying, right?). I got them soldered up and finally the bike was running.
Issue #3) I had bought a gear shift sensor, but the cable from it to the motor was too short (about 8" too short) - so I needed to buy an extension. Unfortunately, the extensions are only 1m long (~40 inches), so way more than I needed, but once i got it I just looped up the excess cable to try it out. At some point in the future, I'll probably cut and splice the line so the sensor has the "right length" cable on it, and I'll have a somewhat shorter extension left over (or two ends that are waiting for other purposes). Not a big deal, but be aware the gear sensor has a pretty short cable.
Issue #4) I would have bought the factory hydraulic brake levers with the eBrake cutoff capability, but they were out of stock when I ordered. I see today they aren't even listed any more. Instead I got the magnetic (hall effect) switches that come with a couple small but powerful magnets. The issue is I can't figure a good place to mount them on the brake levers that came on the bike - so I left them off. By and large this hasn't been a problem riding (since I'm commuting). Stopping pedaling causes the pedal-assist to cut out (with a bit of lag) - and it's not been a riding hazard for me so far. I may revisit this issue to see about some way to fashion a mount (maybe 3D print?) for the magnets. If you're riding off road (trail riding) I suspect that you're going to want to be sure these are installed.
By and large that's it - I put it together and it rides great. Let me describe some options I took and what I think about them now:
Since I am aiming to commute, I built the bike for speed (not power/torque for hill climbing), and I went with the largest chain ring (52T) I could. Even at that, I still mostly live in the smallest 4 or 5 cogs in the cassette. I'm glad I didn't go smaller than the 52T. The middle of the cassette lines up well with the chain ring (a bit hard to see here)
I have the c965 computer - doesn't seem to be an option at Luna any more, but I am happy with it. Might have opted for the full color display, but $45 seemed like too much of an upcharge.
The crank arms that come with the BBS02 are 170mm. After riding a bit, it felt "small" to me, so I swapped back on the 175mm's that came on the stock bike. I had to unscrew the chain rings from the right side (still have the 4 arm spider) and this feels better. I couldn't find a right hand side 175mm arm with the square taper hole, so I either need to live with the spider, or perhaps machine/grind it off. Maybe you could just get another left arm - and then use two left pedals, presuming you don't want clipless or something else that's "oriented" R vs. L...
As noted in other posts/blogs, the BBS02 Pedal Assist takes a bit of getting used to, but it's not that bad. Think of it as "cruise control" - in PA-Level1 the bike wants to go ~15 mph - no matter how hard you pedal. If you're going less than 15 mph the motor kicks in to help. If you're going 15 mph or more, there no motor assist. PA-Level2 = 18 mph, PA-Level3 = 21 mph, etc. The exact speeds for each level do seem to be impacted by what you set as the top speed for the motor. As you increase the top end speed, the various levels seem to spread out (and increase) a bit.
It also seems like if you exceed the "PA-Level" speed that the motor is working against you. In other posts I've seen people speculate that you're actually back driving the motor (or some portion of the gearing / clutch). That seems very likely to be the case based on how it feels to pedal.
In the end this was a fun build and an even more fun ride. However the frustrations that came with Luna leaving out $3 of parts needed to actually be “a kit†(when I paid $1100 for the kit), were really unnecessary. If you’re buying your parts from Luna, you probably want to go get the aforementioned items (2 longer screws, washers, and some connector – I used XT-60), or you’ll be cursing them as well…
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