JDMopar's KHS BBS02 Mid-Drive Build Thread

1. Thanks amberwolf...I'm still learning the terminology but yes I find the geared rear hubs appealing for greater ease of unassisted pedaling.

2. Thanks for the tip on Cordura, good to know!

3. Yes they salt the dickens out of the roads here. I've already replaced the frame on my Dodge and currently I'm in the process of patching up the rotted back half of a Chevy frame...I hate salt.


I'm trying to decide on components for the bike. I have the Shiver but it's heavy and the 20mm thru-axle is silly over-kill. Still might just go with it because I own it and have no other use for it, but I'm debating buying a nice light Rockshox SID or Reba instead. I also have to find out if the chainstay will clear a big single chainring and still have a good chainline.

Ooh just found something out. That KHS is for 26" wheels but I can squeeze the 27.5x2.2 from my mountain bike in the rear end. And 650s shouldn't be an issue with the Shiver fork. So I think I'm going to go with 650b wheels! Yay for keeping up with the times haha.

Better to go smaller wheel, you get more torque, less speed, everything runs cooler.

Before you decide on which wheels to use, you might want to look around at the tires you'll need to use for the weather the bike is to be used for, and make sure they're available in the size for those wheels (and that they'll fit inside the frame/fork for that size wheel, given the diameter/width of the rims/etc).

QUOTE. 'll keep it as reliable as possible. I'll go with cheaper Shimano hydraulic discs (with which I've had fantastic experience and are very reliable), probably a Deore XT or SRAM X9 1x9 drivetrain with a 40 or 42 tooth front ring, dual sided platform/SPD pedals, some nice 26x1.75 semi-slicks for summer and studded for winter.

I would seriously consider upping the front chainring size or your legs will run out of revs.I only have a 36v 500w system that originaly had a 42t f and 11t r and i could never peddle fast enough,I now have a 52t f and find that a lot better.

andy1956 said:

QUOTE. 'll keep it as reliable as possible. I'll go with cheaper Shimano hydraulic discs (with which I've had fantastic experience and are very reliable), probably a Deore XT or SRAM X9 1x9 drivetrain with a 40 or 42 tooth front ring, dual sided platform/SPD pedals, some nice 26x1.75 semi-slicks for summer and studded for winter.

I would seriously consider upping the front chainring size or your legs will run out of revs.I only have a 36v 500w system that originaly had a 42t f and 11t r and i could never peddle fast enough,I now have a 52t f and find that a lot better.

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I thought of that but I'm not sure the chainstay will clear much bigger. I'll have to test fit one of my road cranksets I have around.

So I've dived in head first. I decided to go with the BBS02 mid-drive motor from Luna Cycles. I rethought my desires and thought that it's not unlikely that I'd like to try some of the really steep fire/utility roads around me so the torque would be appreciated. I greatly appreciate all the advice and sorry I wasn't sure yet of what I wanted when I started this thread.

As far as the rest of the bike, I'm going to try to keep it lightweight, so in the event that I ever remove the motor I'll have a decently light mountain bike compared to my beefy Mountain Cycle. I have purchased an SLX drivetrain but I still need wheels, brakes, pedals, seatpost, saddle...also I'm debating getting a lighter fork with lockout.

On the subject of wheels, I might be building my own. I noticed that both Sapim and DT Swiss market spokes for e-bikes (models Strong and Alpine respectively), and do not recommend their standard spokes for e-bikes. I'm guessing that this advice is mostly directed at hub motors. In your practical experience is this something that's relevant for mid-drive motors, or can I go with the standard DT Competition/Revolution spokes that I've always used? Note that I'm not really going to be thrashing this bike on MTB trails, not least of all because the motor is directly exposed beneath the bottom bracket. I think I can go with the regular butted spokes, anyone agree with that?

Thanks all for your assistance.

JDMopar said:

Ooh just found something out. That KHS is for 26" wheels but I can squeeze the 27.5x2.2 from my mountain bike in the rear end. And 650s shouldn't be an issue with the Shiver fork. So I think I'm going to go with 650b wheels! Yay for keeping up with the times haha.

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Yay! for paying extra for the same thing in a 4% different size, and cutting way down on parts availability, and taking away your option of using fatter tires. Um, wait a minute....

JDMopar said:

So I've dived in head first. I decided to go with the BBS02 mid-drive motor from Luna Cycles. I rethought my desires and thought that it's not unlikely that I'd like to try some of the really steep fire/utility roads around me so the torque would be appreciated. I greatly appreciate all the advice and sorry I wasn't sure yet of what I wanted when I started this thread.

Click to expand...

The BBS02 is a bargain and has worked nicely for me so far. However, it has a limited selection of chainring sizes and chainline options compared to BBSHD. I find that only the outer 5 out of 8 gears on my cassette work smoothly without complaint, and without dropping the chain in front. I moved a selection of gears representing the entire range into those positions. That's satisfactory for my use, which is a cargo bike ridden on the street. But if I really needed my whole selection of gears, or lower gearing, I could get it by using BBSHD and one of the many different chainrings available for that system.

On the subject of wheels, I might be building my own. I noticed that both Sapim and DT Swiss market spokes for e-bikes (models Strong and Alpine respectively), and do not recommend their standard spokes for e-bikes. I'm guessing that this advice is mostly directed at hub motors. In your practical experience is this something that's relevant for mid-drive motors, or can I go with the standard DT Competition/Revolution spokes that I've always used? Note that I'm not really going to be thrashing this bike on MTB trails, not least of all because the motor is directly exposed beneath the bottom bracket. I think I can go with the regular butted spokes, anyone agree with that?

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I recommend 14-15ga butted spokes for e-bikes, with or without a hub motor. If the hub holes are too large, you have to use washers to prevent the heads pulling through.

The thicker the spokes, the easier it is for them to become slack under riding loads, and therefore the easier it is for the nipples to unscrew over time. So paradoxically, the heavier the loads and forces on your bike, the more important it is to use butted spokes.

Always, if you need to beef up your wheels, start with the rims. Spokes must be thin for best results.

JDMopar said:

I noticed that both Sapim and DT Swiss market spokes for e-bikes (models Strong and Alpine respectively), and do not recommend their standard spokes for e-bikes. I'm guessing that this advice is mostly directed at hub motors.

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I don't see why they wouldn't use them--they work perfectly, and much better than the thicker stuff that usually comes on the motor wheels.

I use Sapim double-butted 13/14g (from http://ebikes.ca ) on my radially-laced 20" motor wheels on CrazyBike2 and SB Cruiser, which are really heavy and haul multi-hundred-pound loads and/or St Bernards (on the trike they ride in a carrier on the cargo deck).

I've broken a motor axle from a pothole while loaded up, but no spokes.


I could probably have gone 14/15g without a problem.

Chalo said:

Yay! for paying extra for the same thing in a 4% different size, and cutting way down on parts availability, and taking away your option of using fatter tires. Um, wait a minute....

The BBS02 is a bargain and has worked nicely for me so far. However, it has a limited selection of chainring sizes and chainline options compared to BBSHD. I find that only the outer 5 out of 8 gears on my cassette work smoothly without complaint, and without dropping the chain in front. I moved a selection of gears representing the entire range into those positions. That's satisfactory for my use, which is a cargo bike ridden on the street. But if I really needed my whole selection of gears, or lower gearing, I could get it by using BBSHD and one of the many different chainrings available for that system.

I recommend 14-15ga butted spokes for e-bikes, with or without a hub motor. If the hub holes are too large, you have to use washers to prevent the heads pulling through.

The thicker the spokes, the easier it is for them to become slack under riding loads, and therefore the easier it is for the nipples to unscrew over time. So paradoxically, the heavier the loads and forces on your bike, the more important it is to use butted spokes.

Always, if you need to beef up your wheels, start with the rims. Spokes must be thin for best results.

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There are tons of options for 27.5" now! There's basically nothing you can't get for a 27.5 that you can for a 26, except for low-end options which don't concern me. 27.5" is moving fast to replace 26" wheels (just look at all the options for higher end mountain bikes, 26" is gone), but I agree there's not a hell of a lot of practical riding difference. The frame clears 2.2" with quite a bit of room to spare though I don't know why I'd really want to go bigger than that, also it doesn't look like a 26" could really clear any wider of a tire due to the design of the rear triangle. Besides which I like that my current mountain bike runs 27.5 so things will interchange.

Yeah, not sure how well the drivetrain will work but I hope to use a nice narrow-wide chainring (edit: I purchased the 104 BCD chainring adapter so my options are pretty open) to keep the chain on. I don't foresee problems except perhaps a limited front ring size because of the chainstay...not sure on that yet.

Thanks for the advice

amberwolf said:

I don't see why they wouldn't use them--they work perfectly, and much better than the thicker stuff that usually comes on the motor wheels.

I use Sapim double-butted 13/14g (from http://ebikes.ca ) on my radially-laced 20" motor wheels on CrazyBike2 and SB Cruiser, which are really heavy and haul multi-hundred-pound loads and/or St Bernards (on the trike they ride in a carrier on the cargo deck).

I've broken a motor axle from a pothole while loaded up, but no spokes.


I could probably have gone 14/15g without a problem.

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Thanks, I really appreciate you relating your personal experience! I'll be sure to get good rims but I'll probably do the 14/15 butted spokes.

Okay so I've ordered almost everything I need for this thing...but first of all following this update should I let this thread die and post a build thread elsewhere, with a more relevant title? Where's the best place to post?

Quick update...

I've ordered almost everything I need for this project, which includes:

Manitou Marvel Comp fork with remote lockout (yep decided not to use the Shiver)
Stans Arch MK3 rims
Sapim Race spokes with locking nipples
Novatec hubs
Deore M615 brakes 203mm front/160mm rear rotors, also ordered the motor cut off switches
SLX drivetrain

I already have some spare handlebars and stem, so that just leaves a seatpost, saddle, headset, and pedals...and rear rack...and a better rear light, and a thousand other accessories.

Oh and tires! Taking advice there, I want some fast rollers that won't kill me off-road. I've ridden and enjoyed the Specialized Fast Traks so those are on the shortlist but other appealing ones include the Kenda Small Block 8s and Geax Saguaro. I would enjoy a 2.1 or 2.2 in the back at a 2.3 in the front.

Thanks all again I appreciate the advice and I'll probably start a new thread somewhere when the work begins...

JDMopar said:

Okay so I've ordered almost everything I need for this thing...but first of all following this update should I let this thread die and post a build thread elsewhere, with a more relevant title? Where's the best place to post?

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If you want to keep all the decision-making/info/etc in one place (for reference later, for instance), you can just edit the first post's title to be whatever you want. You can also edit the text to add info, or pointers to different parts of the thread, etc.

Or you can start a whole new thread, and then link it in a post in this one (so people know "where you went", if you like.

Great thanks! I'll edit this thread.

I'm sure it'll be at least a month before all the parts are in and this thing is all done, but I'm doing what I can in the meantime. I knocked the old headset cups out and removed the old bottom bracket, removed some old stickers and the residue, and cleaned up the frame. It's not in terrible shape but just dinged and scratched enough to be a perfect beater frame.

Right now I'm thinking about how to secure a rear rack. There are no rack mounts at all. That's no problem for the upper rack stays as a combination seat clamp/rack mount will do the trick nicely. For the bottom I could do some sort of p-clamp arrangement. Alternatively, I'd love to make use of the old v-brake adapter mounts on the seatstays (see picture below). If I could, I don't think I'd need any supports going all the way down to the dropouts. I'm sure I could make something easy and sturdy out of steel, but I want aluminum. One problem is that I'm not equipped to weld aluminum, and another problem is that I'm only a mediocre welder with steel so alu fab probably wouldn't turn out so nice. I'd like it to be strong, light, and not terribly ugly.

I've got one weird idea kicking around in my head that involves a couple mangled IS > Post mount disc brake adapters...

There's a lot of rack info here on ES about prefabbed racks, but not as much about DIY ones. However, it's still useful, as there's failure info about why and how different mounting points/solutions fail.

If there's any way to make a rack that mounts to your wheel axles (since there's no other hardpoints down there), it'll be stronger than P-clamps. You can make the mounts do double duty as torque arms if you are using a hubmotor, too, though there's no need of that with a middrive.

Or you could make a rack that instead of vertical supports is made as a "wedge" frame, whose lower sides parallel the seatstays. THen drill holes in the rack to align iwth the bolts in the stays, and tightly bolt the rack wedge to the stays. Then it can't wiggle.


It also depends on the purpose for the rack; if you're not gonna carry much on it, it's not a big deal. But if you're gonna use it for a battery, or other heavy (5-10lb+) cargo, it's important to stiffen the rack laterally so it doesn't wag the tail of the bike, which can make handling (especially while pedalling) terrible, and eventually stresscrack the rack's mounts and cause it to fail (at the worst possible moment, of course).


One example of super-duty rack
https://endless-sphere.com/forums/viewtopic.php?f=3&t=85317&p=1247409&hilit=Bill%27s+bike%27s+rack.#p1247409

Thanks amberwolf,

I think what I can do is drill and tap the dropouts for the bolt threads (M5 x 0.8 ), then use a disc-specific rack to clear the caliper. Then just to be safe, I'll use long bolts that thread past the inside of the dropout enough to put a nylon locknut on the other side. The dropouts are pretty thick on this frame, I think it'll be sturdy enough. Due to the length of the bolts I would still like to use some with high shear strength, 8.8 or 10.9 if I can find them.

I already have a Topeak MTX rack on my gravel grinder and a slide-on bag specific for that rack, so I guess I'll go with this guy:



It's rated for 55 pounds, which will be enough. Not sure I'll ever have that much, but occasionally 30+ pounds for sure.

I appreciate your ideas! You're a wealth of knowledge.

Time for a little update, even though my progress barely warrants an update.

I'm still waiting on the motor and battery from Luna. That's taking a little longer than expected but I don't care at all because for some reason almost every other one of my orders is taking even longer. Outside Outfitters haven't even shipped my rims and spokes after 11 whole business days.

But I got a few things. The only progress to note is that I pressed in the headset (FSA Orbit MX) and I drilled and tapped the holes for the rear rack. I drilled them low because I want to keep the center of gravity as low as possible. Turns out they *might* be a slight bit too low for the rack to clear the tire. I've test fit another 650b I've got and I think the clearance is TIGHT. That's fine and really exactly what I want, unless of course it's too tight. I'm pretty sure it's good, but it's impossible to tell without the fork and front wheel on to see the angle the rack needs to be to be level.

But I have or have ordered every part I need, so hopefully this starts coming together in the next couple weeks.

I have received my Luna order, and I can report that the order is complete and VERY well and safely packed. So far I'm pleased with their service and also pleased that such an online store exists to help newbies like me who just want to enter the world of e-bikes without a ton of DIY. Normally I love to do my own design and fab and learning as I go, but I don't really have time for that at the moment and just want a working bike as soon as possible.

I'm very happy to report that the 48 tooth Bafang chainring works with plenty of clearance on my KHS frame, which was quite unexpected and a very welcome discovery. I'm not sure I'll stick with the 48 tooth but I'll likely start out with it to see how it feels. When I decide what size I want, I plan to use the Luna 104 BCD adapter to install a nice narrow-wide ring.

In the meantime I'm waiting for my Outside Outfitters order to ship which is supposed to bring my rims and spokes. Very disappointed in them, both with the shipping delay and with their email response time. A week ago they said there was a "backup" at their warehouse. I gave an ultimatum earlier today that if they can't ship by the end of this week then I'm canceling the order. No response yet, if tomorrow brings more silence then I'll be filing a dispute with Visa. On the off chance you were going to, I strongly advise not to order from them.

More pictures soon.

Sorry to leave this thread orphaned for so long. I've been quite busy, but I have finished the bike and have put about 350 miles on it. I was beating the crap out of it so actually I managed to stretch the chain to replacement spec (~1/16" over 24 links) in 300 miles. I'm taking it much easier now after the novelty of how damn fast it can go has worn off.

No major complaints so far. Trying to stop a creaking from the bottom bracket under heavy torque but otherwise it's good!

I really would like some short travel full suspension frame eventually.