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Winter Project. BBS02 on Marin Muirwoods.

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    Winter Project. BBS02 on Marin Muirwoods.

    I've been doing a lot of research for a winter e-bike build and thought I'd lay out my thoughts here to share my reasoning for others who are considering a build and to get some feedback from others more experienced. I've certainly benefitted from what others have posted and it's time to share. I primarily use my bike to commute to work, 5 miles each way, but also use it to run errands and get around the suburbs and into the city.

    I purchased a Marin Muirwoods to use as a donor bike. It's a 4130 CrMo steel self-described "rough and tumble commute machine" with Tektro Auriga hydraulic disc brakes and a 9-speed Shimano Alivio rear derailleur. Weighs about 28 pounds. Got lucky and saw it brand new on deep discount (LT $500 tax included) at a LBS a few weeks ago. The 68mm bottom bracket is ideal.

    I'm planning to add a BBS02 mid-drive over the winter. Luna is my winner for the kit. Here's my order from Luna that I placed a few days ago:
    • Bafang BBS02 750w Mid Drive eBike KIT (Sprocket Size: 48T, Full Color Display, Bafang BBSxx Universal Thumb Throttle, Magnetic sensors to use your own brake levers, Bafang Programming Cable, Mighty Mini 52v GA, 52V Advanced 300W Ebike Charger
    • Luna Cycle Mighty Mini Battery Pack Seat Case
    • LUNA Wrench BBSHD and BBS02 Mid Drive Installation Tool
    • $1050 including shipping

    Here are some thoughts I went through in researching and thinking this out.

    Hub vs Mid
    I started out like many thinking a simple 250w hub kit was all I wanted. Just travel my 5 mile commute to work and be a little less sweaty. I was interested in the 250w hub motor partly because it's such a stealth approach but also because I felt I could fairly easily add it and remove it from my bike: one bike to rule them all! Another dream was to be able to install it on other bikes to share the electric experience with others on group rides while I pedal along with them w/ no assist. I was thinking about a super-simple kit that had the hub motor, battery, and on-off switch on the handlebar. At 150 pounds, I'm light and I'm willing to pedal along so I still feel this would have been reasonable. But as I read more and more (and started travelling greater distances on my bike) I came to the conclusion I wanted more speed and power. I researched the hotrodding path but came to the conclusion I'd fry a 250w hub motor. Then I started looking at more powerful hub motors but they were bigger and more obvious. And heavy. I had frequently come across the bbs02 in my research but blew it off for months because "I didn't want a mid-drive". Then one day something just clicked and I started giving the bbs02 more consideration. It's fairly stealthy with its mounting point below the bottom bracket. Check. The controller is integrated so I don't have to carry another brick. Check. I can tweak the programming. Check. It mounts about as low as you could mount a motor which is great for weight distribution. Check. I had to give up the dream of easily moving it from bike to bike. Okay, don't like but let's keep talking. In exchange I get to use the rear derailleur as a transmission. Bonus! 25+mph. Bonus! Hmmmm….yes, this is for me. Mid drive it is.

    Prebuilt vs DIY
    A lot of really cool prebuilt ebikes exist. It would have been an easy choice that would have gotten me into an e-bike much faster and with LBS support. I went to a LBS and tried a Trek. It was fun but it just didn't feel right to cut out at 20mph, I can pedal that fast and I knew I wanted the ability to go faster. I just didn’t feel it was worth the sticker price. A different Trek that does 28mph is close to $3,000. With DIY, I like the idea of being able to tweak the programming. I live in the suburbs and when I commute to work I'm frequently the only bike I see -- I'm not going to bother anyone going 25mph on the side of a 55mph highway. Plus I'm making a small hobby out of this DIY project, I like the lower cost, and have enjoyed learning more about wrenching, motors, controllers, and batteries.

    Steel vs Aluminum
    Steel won for me. I just didn’t feel comfortable with aluminum knowing the BBS02 bites into the bottom bracket to help it stay put. I also like the softer feel of the ride and it's such a reliable and dependable material. It appears many people have had successful builds on aluminum and Luna is using them on their own builds which I'm sure they stand behind but the aluminum bikes I was looking at were 25 pounds themselves, upwards of 30 with a front suspension and with the Muirwoods donor bike coming in at 28 pounds, just three more than the comparable aluminum models, I felt more comfortable with steel.

    Other bikes I considered:
    • Trek 750 Multitrack (steel, used, rim brakes)
    • Trek Zektor 2 (aluminum commuter w/ disc brakes)
    • Trek DS2 (aluminum, disc brakes, front shock)
    • Norco Indie (aluminum, disc)
    • Novara Buzz (aluminum, disc)
    • Cannondale Bad Boy (aluminum, disc)
    • Fuji Police Bike (aluminum, disc brakes, front shock, 26" wheels)
    • Luna makes a fully assembled e-bike out of the KHS Police Bike

    The Muirwoods was also an interesting combination of lower-end Altus front derailleur (which I didn't care about because it'll be removed) and the next level up rear derailleur from the Alivio line. At least I didn't pay a premium for a front transmission I won't be using.

    Disc vs Rim Brakes
    I bike in all types of weather and with the increased speed I wanted disc brakes for consistent performance regardless of conditions. I wound up with hydraulic but feel like I could have been just as happy with cables, and maybe even happier, because mounting e-brake cutoff sensors appears to be a challenge because of the way the hydraulic levers work. I'm sure I'll have to tinker with this a bit.

    Suspension or No
    I went without. I currently commute on a Masi CX cyclocross bike with 700x28c tires. It's a steel frame with no suspension. I travel up to 30mph on the big downhill portion of my commute with no issues or complaints. I have no problem lifting off the seat to avoid bumps and potholes. The Marin donor bike has 700x40c tires which should provide additional cushion from where I'm at now with 28c. For me the front shock just seemed like extra complexity and weight I didn’t need. I'm not planning to ride singletrack or do any substantial off-roading. In short, I plan to ride this like a bike, not sit on it like a motorcycle, so I feel comfortable I'll be fine w/o a suspension.

    Gear Ratio/Inches and Wheel Size
    I wanted a wide range back cassette to be able to control the load on the motor to prevent overheating on hills and to be able to go fast on the flats. I wound up with a 12-36 cassette in the rear. Perfect. The existing front chainring is 48/36/26. Since I've already got a 48t in the front I got the 48t Bafang chainring and I think this will work great with the 12-36 in the rear. The front-back 48-12 gearing paired with 700x40c wheels should provide a very reasonable cadence of 77rpm at 25mph. Calculate your cadence at speed.

    Flat or drop bars
    Went with flat mainly for safety. I can be upright riding in traffic with good vision and I can keep my hands right on the brakes where I've got options for emergency stopping/skidding. I might add bar ends for some additional riding positions when not in traffic and for use when out of the saddle.

    I ditched the hub motor but I'm still wanting to make this build as stealthy as possible. I'd prefer not to have a shark pack or bottle mounted in the triangle. I might regret not having the battery locked to the frame but I don't think I'd be able to trust the lock. How do others feel? In what conditions do you leave your $500 shark pack locked to your frame when you lock up your bike? I went with Luna's mighty mini, the 52v x 7Ah version with the GA cells. Sure, it's got limited range, but it would easily get me to work and back (10 mile RT). I thought I'd start with one and maybe work my way into another to extend my range. This battery is small. It would easily fit in my saddlebags, in Luna's seat bag (which I purchased), in a third party seat bag like this, maybe on my rear rack with a custom mount, or possibly I could make something to store it inside the main triangle using the two sets of bottle cage bosses on my frame. It's 6x2.75x3.25 inches -- that's pretty stealth. At 3.3 pounds it's light enough and small enough to carry along with you. At 110Wh/pound it's the most dense battery I've found. I wanted to get a feel for exactly what it would be like so I made a scale model by cutting up and re-gluing a cracker box and filling it with some padding and coins to 3.3 pounds. I know, #geekalert, but it's really given me a good idea of what it would be like.

    Tools I already own

    Tools and supplies I bought specifically for the build
    TIP: If you don't know much about removing cranks or bottom brackets this video from Park Tool cleared it up for me.

    Here's a picture of some of the tools and supplies.

    Still need
    • C-spanner tool and bottom bracket cup wrench. I bought the Luna wrench which does both.
    • (Might need/want) Moldable rubber like Sugru or Versimold. This could be useful for mounting the brake sensors or providing some cushion for the battery.
    • I may need a small grindstone for an electric drill as there may be tiny bits of weld inside the BB. Or a Dremel. I'm hoping I don't need this and my BBS02 will just slide right in.

    Something you might need that I don’t
    • Chain breaker if your chain doesn't have a missing link and you want to remove your front derailleur you'll need to break your chain. My chain has a missing link -- there's a tool for that too but it can be done by hand or I've seen some hacks using a wire. I'll take my chances on this and if I have trouble I may need to get a special pliers-like tool to get the missing link apart. Here is a good video that explains a lot about chains.

    My background
    This section I'm writing just to give other noob builders out there some idea of my background as I embark on this project. I've read a few posts from people that felt they were fooled into taking on a bigger project than they could handle after hearing that a DIY e-bike build is "easy". My hope is that this will help you calibrate your own chance for success as I go through my own build. Here goes:
    • I've done basic bike maintenance like changing tires and adjusting brakes.
    • I recently assembled a brand new single speed bike shipped to my house in a box.
    • I've never pulled off cranks or a bottom bracket.
    • I own a home and do much of the maintenance myself. I change out the mower deck and snowblower every year on my tractor. I've done some small remodeling projects like finishing a roughed-in bathroom but that was near the limit of my desires, abilities, and tools. I've dabbled in woodworking and have power saws, drills, and sanders.
    • After reading and watching a ton of material over the last few months, with the set of tools I own, and the few purchases I've made, I'm feeling prepared to get going on the build.
    • In summary, a mid-drive install is not something you do at home with "mother's toolbox". You need some special tools and knowledge. But it is within the reach of mortals -- you don't need to be a mechanic to do this. Or so I think. Time will tell. ;)

    Bike Prep Stage 1 -- Fenders, Rack, Remove Front Derailleur

    Today I installed anAxiom Journey Rack, a set of Planet Bike Cascadia Fenders, and removed the front derailleur.

    Installs for rack and fenders were easy. I had the rack already and I was pleasantly surprised to find it fit even with the disc brakes -- it's not a disc brake specific model but it was no problem at all. The fenders took some tinkering to get them to sit straight but all the spacers and long bolts I needed were supplied in the kit. Planet Bike provides a ton of extra hardware options like spacers and 45mm bolts. Here are links to pictures of the 2 instruction pages page1, page2 -- they have a complete parts inventory. Tire clearance on the back fender is a little tight mainly because I have the rack tilted back a bit -- I'm thinking about mounting my Mighty Mini battery between the rack and the seatpost/downtube rather than suspending it from the seat. With my life size model of the battery I built I can see that I'll have just enough room. We'll see how it works when the battery arrives.

    Removing the front derailleur was pleasantly easy. No glitches. To break the chain I simply took the two ends of the magic link and, with my hands, pushed them together and voila, it snapped open. Here's a picture of the magic link after it had been separated.

    Then I detached the cable, removed the derailleur mounting screw and, with the chain out of the way, the derailleur came off. I pulled off the handlebar grip with nothing more than slow steady pressure, no soap or anything. Then it was just a matter of loosening the brake lever and removing it so I could loosen the shifter and remove it. Really very simple and no surprises.

    This is going better than expected. Hopefully it stays that way.

    Fenders on, rack on, front derailleur off.

    The Muirwoods donor bike has ample braze-ons and mounting points for the accessories. The back, where both the fender and rack attach, has two mounts so I didn't need to double anything up.

    View from the drivetrain side

    Bike Prep Stage 2 -- Clear the Bottom Bracket

    I wanted to clear the underside of the bottom bracket for the motor. The cable for the rear derailleur was routed underneath the bottom bracket but veered substantially away from the down tube. I would guess about 5mm. If I left it like this I would have had to tilt the mid drive away from the down tube 5mm or more to avoid the cable and I wanted to have the motor tilted up as far as possible for clearance. This might have been overkill but I wanted to try to clear under the BB.

    Here's how it looked when I bought the bike. Left to right is the rear hydraulic brake line, the front, and then the rear derailleur cables.

    In this picture you can see how far the rear derailleur cable is away from the down tube.

    Side angle:

    In the picture below I've already removed the front derailleur and you see the brake line, rear derailleur cable, and cable guide.

    Last picture before any changes. Here's how it originally finished off at the derailleur.

    The solution was to buy ~5 feet of cable housing to make the entire trip from the shifter to the rear derailleur. Jason at The Hub Bike Co-op in Minneapolis was nice enough to measure out the correct length for me and he even threw in a couple metal end caps. Installation was pretty simple. I took the terminal cap off the end of the existing cable and pulled it through all the way up to the shifter removing the two existing housing segments. I then routed the cable through my new housing and reattached at the derailleur. A few strategic zip ties hold the new housing in place and I'm all set.

    Prior to starting, it helped to shift into the highest gear in the rear (smallest sprocket) and then take tension off the derailleur and cable before detaching the cable -- I used a small piece of wire to pull the derailleur toward the pedal, one of the above pictures shows this.

    After reassembly I thought I might have shifting issues but I had very little. I just used a couple turns of a micro adjuster and shifting is working well again.

    The new housing consumed about an inch or two more cable than the previous run. I could have shortened the new housing but I still had enough cable to clamp at the derailleur. I just have less hanging out after the clamp.

    The last thing was to remove the now unused plastic cable guide from the bottom bracket. I now have a clean bottom bracket just waiting for the mid drive to show up. If you look closely at the picture below you can see the new housing for the rear derailleur cable on the right of the downtube. I might move the brake line above the BB when the cranks come off but I'll wait until the motor arrives and see how it looks -- it might be fine right where it is.

    Kit Arrived!

    Kit looks great! Luna shipped my kit within a few days of placing the order. The delivery takes a bit longer than you might expect because the battery requires all-ground travel on UPS. All arrived in good shape but I did have a few surprises:
    1. The battery had an Anderson connector rather than the XT90-S I expected. I filed a support ticket with Luna and after a few exchanges where we considered if I should switch out the connector myself (it's a bit dangerous) we decided it's best to return the battery and let them ship out the correct one. They simply shipped the wrong one. They hinted the one I got was an oddball meant for a different customer. Even dealing with a US-based vendor the shipping is still expensive in the $40-50 range because the battery has sufficient capacity to be considered hazmat. Luna was great and honored their mistake by paying shipping both ways to get me the correct battery. I hate to imagine what it would be like dealing with a Chinese company. Kudos to Luna.
    2. The motor came with the Bafang stock bullet connectors for connecting the battery. For some reason I expected Luna would ship the motor with a pre-installed an XT90-S connector. In hindsight this is just something I missed. Not a big deal, I just need to solder in the new connector when it arrives with the new battery. But I'll suggest to Luna that they should sell "kits" whose electric components work together without this extra step. It would be simple enough for them and it would make installing the kit just that much easier for DIY'ers. Maybe add it as an extra add-on for a small fee?
    3. With the confusion on the battery I got a bunch of extra connectors and things I don't think I need. I asked Luna about it and they said just keep it.

    Just one other comment about the shipment. It was sent UPS with signature required. For me it was easiest to ask UPS to route it to the nearest UPS store which worked out great. I have a UPS account but I think you can do this with nothing more than the tracking number.

    Here's a picture of the full kit that I received.

    Here's a close up of the motor. You can see the bullet connectors. I've got to practice my soldering a bit as I'll need to solder on a new XT90-S connector.

    And this is a picture of the battery connectors on the battery I received initially. The red/black is an Anderson connector. I was expecting the XT90-S for its anti-spark system which you can see demonstrated in this video.

    So I've had a little delay but things are progressing. In the meantime I can get started on a few things like mounting the
    display and throttle. I can also pull the cranks and remove the cartridge from the bottom bracket.

    Bottom Bracket Open, New Battery Arrived

    Pulling cranks and removing the bottom bracket cartridge was a breeze. I had the right tools and it's a new bike so things came apart just as expected. Here's some bottom bracket art. I might have to make this my avatar for the forum.

    I'm thinking I'll do a future post with more about component weights. But for now let me just say that I've pulled 4.7 pounds of equipment off the bike at this point. That's made up of cranks, chainrings, bottom bracket cartridge, front derailleur, front shifter, stock rear derailleur cable housing, the small plastic cable guide that was under the BB, and the stock pedals because I got some replacements that take the pedal straps that I like. Added on so far are the new housing for the rear derailleur cable, the rack, and fenders. With the empty bottom bracket, fenders, and rack I just weighed the bike and I'm right back at 28 lbs. If I tally everything else I'm adding I'm figuring on being just shy of 44 lbs including battery. Not too bad and right in line with what I expected.

    Speaking of battery, the new one arrived and has the XT90S-S connector. Awesome. I was surprised to find it has a voltage meter installed in it. Maybe one of the pictures on the website has a hint of it, but there's a clear picture of one without. At any rate, it's an interesting addition to a battery that prides itself on being small and light. The meter is probably part of what makes the battery a bit bigger than spec'd and a bit heavier. Mine came in at 3.7 pounds. Still light but significantly over the 3.3 lb advertised weight. I doubt the meter consists of the entire 0.4 lb difference from spec as the original one I was shipped weighed 3.5 lb and did not have a meter. The dimensions are also different than the spec on the website. 6 x 3.25 x 2.75 inches? Not exactly. Mine is 5.9 x 3.5 x 3.125. Not really significant, but different. Here's the kicker though. It's a really tight fit into the saddle bag I bought direct from Luna. The extra girth is significant when trying to tuck it into the bag. It does fit and I think I'll get more skilled at inserting and removing it as I do it more. So it's fine but it's kind of a pain and I feel like maybe the bag won't last as long because I kind of need to crank on it. If you ask me, I would trade the meter for the smaller size and weight savings. What good is a meter when it's tucked in a saddle bag most of the time anyway? I won't even be able to see it because it'll be in the front of the bag. Hmmm. Pffft. Just part of the fun of the DIY family I guess. :) Still, much better and safer than I could do myself and not a big deal. I’m getting really excited to get this thing assembled and running.

    From looking at this picture of the XT90-S on the Hobby King site I thought the XT90-S came as a set with unique features on both the male and female side. However I was only shipped XT90 (no "s") to solder onto the controller. After some research I've come to the conclusion that one side does all the magic and using a normal XT90 on the other is fine. This thread helped: You only need the S on one side. Which side is it you ask? Male or female? Ha, that's been another small learning opportunity. It depends on if you are talking about the metal connectors or the plastic housing. The female side of the plastic housing has the metal male pins so the terms can get switched if you are not clear. It seems the standard is to talk about the metal fittings and not the plastic housing. Therefore, the female side (with the green) has the magic. I'm mating the female XT90-S (with the green) that came on the battery with a male XT90 (no "s"). If that's trouble, somebody let me know please.

    Moving on, it's time to get soldering. I bought some rosin core solder to make sure I had a good quality solder as I had just a little from my original Weller kit purchased 10+ years ago. A few youtube videos later and I'm out to practice. I got pretty good. Here's one of the later and better products of my practice.

    With practice out of the way it was time to get that XT90 onto the controller. For the most part it went smoothly. The tips of the XT90 pigtail had been, I think, tinned with some solder to prevent them from fraying. I wanted to mechanically join the wires first so I cut that off and stripped a little more housing. The motor I think is a 12 gauge stranded wire. The XT90 has a 10 gauge stranded but boy are the strands fine like thinner than a hair and probably 150 of 'em are need to bulk up to the 10 gauge size. It was a little touchy to deal with. I slipped on the heat shrink tubing first and then it took a little finagling to get the wires mechanically joined but I got it to a point where I was satisfied. Then I went at it to solder it together. I feel that with the super-thin strands it was harder than my practice wires to get the joint hot but I feel like I did okay. I'm sure I got solder into the majority of the joint but I also wound up with a pretty big knuckle. Maybe some flux would have helped. After it cooled I started wondering if my heat shrink was even going to make it over the knuckle. I stretched it a bit and added some dielectric grease and it slid over pretty easily. I did have one tiny strand from the XT90 wire that poked through the heat shrink. This could have been easily avoided if I had just done a final smoothing on the joint. It's a tiny hole. Overall, I'm pretty happy with it. Here's the finished product.

    Next up is assembly. I'm past the most difficult parts. Shouldn't be long now.

    From < solder+#p382376>
    I don't know how experienced of a solder-er you are, but if you want to learn a thing or two this video taught me a lot about soldering -

    From <>
    Watch our video on how to re-program your 965 display to get 9 levels of pedal assist HERE

    One other thing I failed to mention earlier is that I'd like the bike to be rideable without power. I knew I had to carry extra weight with me but I didn't want motor drag. BE (before electric) I would travel up to 25 miles away from home and use a combination of bike and bus/train to get around. This worked, but was a bit slow at time as city buses travel an average of around 14mph and the train about 17mph.

    BBS02 Install

    Motor and wiring installs went smoothly! I just took my time and didn't rush things. With the wiring and motor installed, I've taken it for a couple test runs of 2-8 miles and the performance is great and just what I expected. Wheeeeeeeeeeeeeeeee!!! :)

    I did decide to move my hydraulic brake line above the bottom bracket as the fit was a little tight and it could simplify brake line maintenance in the future. You can see that in a couple of the pictures above.

    The battery in the Luna bag fits snugly between my seat post and my rack. The Velcro on the Luna bike bag is just perfect for attaching to the rack's arms that reach from the rack to the seat stays. It's snug, stealthy, and firmly mounted although I did hear it jostling around a little bit over bumps. Long term I might need another velcro strap.

    I'm going to wait for some final build pictures until after the brake sensors are installed but it's looking pretty boss!

    About the only issue I had with the motor install was that the housing for my rear derailleur cable got pinched in between the motor and the chainstay when I initially tightened everything up. I thought for a minute that the motor was hitting the frame itself and I was a bit spooked that I'd need spacers or something on the drivetrain side however all I had to do was loosen it up a bit, push the housing above the chainstay and then crank it back down. Speaking of cranking, the Luna wrench was awesome; it's the right tool for the job. As others have commented it does take a little maneuvering when tightening the lockring because it only has 4 positions where you can mount the wrench so this limits your choices. In some orientations the chainstay is in the way, in others, the motor. The good news is that with only 4 choices, the best one is pretty easy to spot.

    The only thing I haven't fully installed are the brake cutoffs. I've got them connected to the controller but the magnet is simply fixed to the sensor. They are going to take a little more dinking around. For my test rides I was okay with this set up because the motor will cut out when I stop pedaling and then I just need to be careful w/ the throttle.

    On my test rides I had no chain drops. The chainring sits squarely in the middle of my 9-gear cassette and I used all 9 gears in my test runs with no problems although the chain was a little clickety-clacky (noisy) when shifted out to the extremes.

    I'm in Minnesota and it was a cool day when I tested so I wasn't too worried about overheating. I shifted into my lowest gear and throttled all the way up the big hill in my neighborhood with no pedaling which is about 110 foot rise over half a mile. The display showed 13.5 mph the whole way up. This is exactly the speed reached when running on flat ground in that same gear so my takeaway is that the motor had no problem pushing the total ~200 lb payload up the hill. Not too surprising with a 48x36 gearing. With my bike and that gearing that's around 125 rpm. I've set the wheel size on the display to match my bike but I haven't done any calibrations on how accurate the mph reading is but I think it's in the ballpark. I'll also mention that right out of the box my throttle works in PAS setting zero because I know this has been an issue over the years.

    I must have read about a few people complaining about responsiveness of PAS systems in the past because I knew it was something I wanted to check out. I found that one quarter turn of the cranks and the motor is on. Every time. Stop pedaling and the motor turns off very quickly, like maybe a half second response time. Every time. It is reliable and consistent. This is due in part to the programming settings that Luna sent with the controller. I'm completely satisfied with the responsiveness of the PAS.

    Next up is the brake sensor install.

    Installing the brake sensors

    I was curious about how well the Bafang Hydraulic Brake Sensors would work and how easily they would mount onto my brake levers which are small and don’t have a ton of travel. I need to do some testing to see how much movement is needed to engage the sensor. The video referenced on the Luna site is accurate but simplistic and maybe a easiest-case example. The other link to a how-to-install article on their forum is thorough and has good advice. My case is similar to what's referenced in the forum article in that I have no perfect place to mount the sensor or the magnet. Looks like I'm into some kind of epoxy or glue.

    Sounds like a great time to experiment with the Sugru I purchased. Sugru is a moldable glue that cures to rubber over 24 hours. It makes a strong bond with many materials and yet it won't stick to plastic wrap which allows you to use it in tight spaces. Pretty slick stuff. I'm imagining this will look very clean, much cleaner than epoxy, because you can work with the product for 30 minutes to shape, form, and smooth the edges. Another advantage Sugru has over epoxy is that it's easier to clean it all off and start over if you mess it up. Oh yeah, it comes in midnight black too. Perfect.

    Let's see how this goes….

    First, here are some pictures of how the sensors would mount on my brake levers. The first picture looks like a reasonable fit:

    But as we take a different angle we can see a gap.

    Here is a slightly different position closer to where I actually mounted it, but still a gap.

    You can see the need for some type of glue or epoxy to fill the gap to make a good bond. Without it, because of the shape of the brake lever, just a minimum of the supplied adhesive would come into contact where I need to mount the sensor. Sugru seems like an ideal choice. I plan to strip off the provided mounting tape and go all-in with Sugru. I briefly considered ripping the plastic case off of the sensor and just mounting the now-much-smaller device completely enclosed in Sugru but decided against this approach. More on using Sugru later.

    Next up was testing the sensitivity to get a feel for the positioning and consistency of the sensor. In all, I'm very impressed. The switch provides consistent on-off operation with a minimum of travel. If I set the magnet about 4mm away from the sensor I need only 1mm of additional separation to disengage the motor. Every time I let go of the brake lever, the motor turns back on. Nice. For my brake set up, the motor cuts out well before the brake pads are pressing down on my rotor. This is ideal as I'll be able to use just a touch of my break levers like a clutch to momentarily disengage the motor to avoid shifting under load. The length of motor shutoff I consider to be short. I think this is adjustable in the Bafang programming/setup but however it's set if I just tap the brake lever I get half a second of motor disengagement. If I hold the brake lever for a second or more and then release I get more like a full second delay before the motor comes back on. That's a pretty short motor shutoff. I think I'll have to experiment to get the right technique down when shifting. And if I'm still crunching gears when shifting I might want to monkey with the programming to extend the delay. But that's another day.

    Here's a picture of my initial sensitivity testing where I used some vinyl tape to hold things in place. 4mm between the sensor and magnet was about right to have a very responsive lever for motor cutout with a consistent engagement of the motor when the brake lever was released.

    To test the sensors I put the bike in the lowest gear (largest sprocket) and held the "-" (minus) button to engage walk-along mode with the back wheel suspended off the ground. This way I could test the sensor operation with the wheel spinning at a slow 1.2mph instead of 15+ mph that the throttle would have kicked in at.

    This may be obvious but the orientation and position of the magnet in relation to the sensor makes a difference in how it operates. The magnet can be mounted in three planes and it can be moved in three dimensions closer or further from the sensor. In my case there only one orientation made much sense -- flat against the brake lever. You just have to experiment and see what works best for your situation. Just make sure to replicate exactly what you tested when you go for the install, especially if you are using glue or epoxy, and even more so if you are working with small tolerances.

    Mid-process I got to thinking, hey, I'm working with a 1mm tolerance here and I know magnets are polarized with a positive and negative. Would it matter if I rotated the magnet? Would it change the sensitivity or operation in any way? Off I went with a sharpie to mark up the magnet and find out. I didn't find any difference. Unless you are trying to work with the smallest of margins I don't think this should be a concern.

    Satisfied with the sensitivity it was time to get going on mounting these bad boys! To get a really good feel for what this process would be like with the Sugru I used some removable office putty to mock up the finished product. This gave me a good idea of how much Sugru I'd need to mount the magnet and the sensor. It turns out about 1 pack per brake lever does the trick.

    Pictures with white office putty.

    I've never used Sugru before so for some extra protection in case the Sugru bonds poorly I first wrapped some fishing line around the magnet and then left a bunch of extra. A small bit of the line will just get molded right in with the Sugru. Eventually I'll tie the loose ends to the brake lever and trim it down. It will hardly be noticeable. If the Sugru fails for whatever reason, I'll still have my magnet.


    The process took some time but wasn't difficult. First, I cleaned everything up with rubbing alcohol to remove any dust, oils, or office putty residue. I removed the provided double-sided sticky tape from the sensors. For good measure I scratched up the bottom of the sensor to give the Sugru something better to latch onto. Then it was just a matter of opening the Sugru, breaking into two pieces and forming it around the gear and onto the brake levers. You could do this in as little as 5-10 minutes but if you want it to look nice several rounds of smoothing are required. A finger works great. Guitar picks in several differing thicknesses helped for tight spaces. Final smoothing is best with a thin layer of dishwashing liquid on your finger. All throughout the process I continued to test the levers to make sure things weren't moving as they cured. Overall the Sugru was great to work with giving plenty of time to shape, mold, and refine. Hopefully I got enough surface area to get a strong bond. The components are light so I'm hopeful it will be a good long-term and durable solution.

    Here's a picture after the Sugru was installed but before it had cured. The orange vinyl tape is to keep things from moving around.

    And here's how it looks after the Sugru has cured. From more than a few feet away it almost looks like a single component. I'm very happy with how this turned out.

    Next up I'll get some pictures of the complete bike.

    Full Build Pictures

    And finally, some pictures of it all put together. I still might try to find a way to conceal the wiring a little better. All in all the bike looks just like what I had envisioned. It's very clean, stealthy, and hard to tell it's a ebike. I commuted to work last Friday (5 mi. each way) and performance was excellent, very quiet, super fun, and easy to ride. This is the coolest thing I've ever built.


      Awesome build. I'm thinking about using a Muirwoods as a donor bike, as I'll be mainly using it as a commuter. So this is definitely an inspiration!


        Just wanted to say thanks for such a detailed post! Lots of good info here, I particularly like how you mounted the brake sensors!