2018 Kona Unit BBSHD Build with questions

saukit

10 mW
Joined
Jan 9, 2019
Messages
28
Hi all,
I decided to go with a Kona Unit as the donor bike for my BBSHD build. While I couldn't find any other cases of someone mounting a mid drive on this bike, it checked a lot of boxes for me (standard BB, steel, rack mounts, 27.5+) and I decided to take a chance.

I picked up a demo 2018 set up as singlespeed, here is a stock photo:
2018 Unit Stock Photo.jpg

This bike can be converted to geared by replacing the dropouts, they run $30 each or so from Kona. I ordered a couple and had them within a week. For the rest of the drivetrain I opted to go with 8 speed as I didn't think I'd need a huge gear range with the BBSHD. I picked a steel Sunrace cassette (11-40t wide range), Sram X5 rear der, Sram X4 shifter, and a KMC X8.93 chain.

Around the same time I picked up the Unit, I also ordered a BBSHD kit from EM3EV. I went with a Jumbo Shark 17ah battery in large part due to the more robust mounting mechanism as compared with an original Shark. From the time I ordered the kit (end of April) to when it showed up at my door was about 3 1/2 weeks. I will say that the shipping info can be a little confusing, you end up with a tracking number that doesn't function for a good period of time. However every time I had a question, Paul and Moon replied promptly and explained what was going on. When I got the kit everything was very well packed, all the items I ordered were included, and I am happy with the decision to go with EM3EV. That being said I also ordered some stuff from Luna, specifically a bunch of spacers and their 42t Eclipse chainring. It arrived promptly and in good condition.

I spent a couple hours on Saturday pulling the crankset and BB off the Unit and started to mock up the BBSHD install. If anyone's interested the self extracting cranks and BB came off easy, the BB was torqued way to tight but nothing a couple whacks with a mallet didn't fix.

Once I had the BB clear, I slid the BBSHD in and the motor housing just cleared the chainstay. However, when I tried the Eclipse chainring there was not nearly enough clearance. So I fiddled around with different configurations and it seems like I have a few options. I'm hoping to get some feedback from you experienced builders on the best way to move forward.

Right now I have two chainring spacers on the Eclipse, from what I can tell probably a 2mm and a 1mm. There are also 8mm worth of spacers on the drive side of the BBSHD. This has provided with a decent chainline (probably won't be able to use low gear but that's ok), but I have barely enough threads to get the lock ring fitted. The jam nut is out of the question. There is also very little clearance (1-2mm) between the chainring and the chainstay.

Chainline:

Unit BBSHD2.jpg

Chainstay/Chainring clearance:

Unit BBSHD4.jpg

Lock ring, this isn't all the way tight but probably not more than 1/4-1/2 turn left.

Unit BBSHD3.jpg

Does the support bracket need spacers now?

Unit BBSHD1.jpg

I think I could probably just bolt all of this together with a liberal application of blue loctite and move on to the rest of the build, but if anyone sees a fatal flaw here I'd appreciate your opinion. Right now it seems to me I'm compromising between chainline and Q factor (drive side is 30mm spacing or so, non drive is closer to 10).

So...

Can I push the chainring out using even more spacers? There is a cylindrical relief on the motor which the chainring fits on. If I space out the chainring so far it doesn't fit over the relief, is that a problem? Would I be better off to use something like a mighty mini? I don't think so as I think the Eclipse has 28mm or so of offset and the mini has none that I'm aware of. I still think this would impact my chainline another 20mm or so.

Is the lockring engaged enough to use loctite and ignore the jam nut?

Would I be better off using a chainring with a bit less offset like the Lekkie? That would buy me a lot more clearance but I feel like the chainline would be terrible.

Just shut up and ride the thing??? Thanks all, appreciate any input!
 
IMO, from BBS02 builds, you definitely need to space the support bracket adequately. On one of my builds (73 mm bottom bracket) I tried to affix the "mounting bolt" with Locktite (no room for the jam nut), but it came loose, so I transferred the BBS to another bike. Others have had success, but it didn't work for me.
 
2old said:
IMO, from BBS02 builds, you definitely need to space the support bracket adequately. On one of my builds (73 mm bottom bracket) I tried to affix the "mounting bolt" with Locktite (no room for the jam nut), but it came loose, so I transferred the BBS to another bike. Others have had success, but it didn't work for me.

Thanks for the input, I did a little research and I think I just don't have enough threads to ensure that the lockring stays on even with loctite. I elected to buy a 42t bling ring which has 4-5mm less offset than the Eclipse. In addition it's 6mm smaller in diameter. Hoping that lets me get the motor centered a bit better without messing up the chainline too much. I'll post some more pics once I get the Lekkie. Bummer that the Eclipse is a waste, maybe I'll find a use for it in the future...
 
On my first BBS02 conversion the gearing was 11-17-28, 8-speed spacing (so, IMO, a stronger 8-speed chain could be used), spaced on the outside end of the cassette which shifted fine, gave a straight chainline (with the middle gear, so the chain was never more than one gear off) and was all the gears needed with the motor. Very inexpensive too with a chain ($8), Altus derailleur ($20) and three cassette cogs ($15 or so) all from Amazon. Eventually purchased Lekkie crank arms to neutralize the 15 - 20 mm right/left offset)
 
Well I ordered a Lekkie bling ring and got a much better fit this time around. I only needed 1 3mm spacer on the BBSHD and about 4mm worth of chainring spacers. This gave me a decent chainline although trying to go the lowest gear throws the chain. Pretty sure I don’t need the granny for a BBSHD so I just screwed the low limit screw in so that the derailleur won’t even try to shift to the low gear.

I hit my next snag while trying to mount the battery. This should have been pretty straightforward but I forgot that this frame has two cable bosses for a dropper post mounted on the downtube. These bosses conflict with the battery mounting plate.

The easiest thing to do seems to be to grind down some of the plastic ribbing on the underside of the mounting plate. I think this should give me enough clearance to get the plate to lay flat. I really don’t want to grind the cable bosses off the frame if I don’t absolutely have to.

Has anyone had experience with removing some of the plastic material off the mounting plate? Can I do this without compromising the integrity of the plate? Thanks for any advice!
 
I couldn't quite tell from the pictures, but be sure the motor is tight against the down tube. You can use a spacer if needed, such as a piece of hard rubber, etc. This will prevent any tendency for the motor to rock back and forth, which is what makes the big crank nut to come loose.

Looks like a nice setup, enjoy.
 
Rassy said:
I couldn't quite tell from the pictures, but be sure the motor is tight against the down tube. You can use a spacer if needed, such as a piece of hard rubber, etc. This will prevent any tendency for the motor to rock back and forth, which is what makes the big crank nut to come loose.

Looks like a nice setup, enjoy.

Thanks, yeah in the pictures I haven’t tightened the motor down yet. Now that I put the Lekkie on I was able to get the main lock ring and the jam nut on. It’s tight against the downtube.
 
Took a dremel to the battery baseplate. Here is a pic, I used yellow tape to outline the outer edges of the grinding area. I really didn't have to take too much material so I'm not worried about compromising the strength of the plate. The plate lies flat now, it may be a fraction of a degree off center but not much.

Now to figure out how to route all the wires. So many...

Unit BBSHD6.jpg
 
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