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2013 Specialized Myka, XS frame BBS02 build

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    2013 Specialized Myka, XS frame BBS02 build

    The following is my wife's Specialized Myka DIY eBike conversion:
    My quest for building out an eBike for her started out months ago as a way to get my wife out & enjoying the trails with me... plus my curiosity over electronics. Most of the trails in the area are either long or steep climbs (or both). So, near the beginning of each ride, she's already miserable and wanting to go back to the car - most of our rides end up getting cut short.

    But thanks to DIY kits from Luna Cycles, I now have a happy mountain biking wife! She still gets a work out (I leave the throttle disconnected so she only has pedal-assist) but she's all smiles to the top. Now, she's the one waiting for us at the top.
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    The thing I really love about this setup is how stealth it looks. At first glance, most people never even realize her bike has a motor. Having the battery in a backpack probably helps in the stealthiness.

    So on to the build:

    Make/Model: 2013 Specialized Myka Sport, x-small
    Cassette: Shimano HG-61, 9spd 12x36T
    Rear Derailleur: SRAM X7, 9spd, (non-clutched)
    Chain - KMC x9.93 stretch-proof, 9spd chain
    Shifter: SRAM X9, twist shift, 9spd
    Brakes: Tektro Drako, hydraulic

    Bafang BBS02, 750W Mid-Drive kit from Luna Cycles - $499
    46T steel chainring - included (not installed)
    Luna Full Color Display - free promotional upgrade
    Bafang universal thumb throttle - included
    Bafang brake levers - included (not installed)
    Magnetic brake sensors - $9 (not installed - awkward to install/use)
    Race Face NarrowWide Chainring & adapter - $49
    Programming cable - $19.95
    Slimline Rear Rack, Panasonic NCRB, 52V, 13.5Ah - $449.95
    Luna Cycle charger, 52V, 300W - $79.95
    Add-Ons to order:
    12ga silicone-insulated wire, 1 meter each of red & blk - $3.19
    XT90 spark-resistant connectors - $2.95
    heatshrink tubing red - $0.49
    heatshrink tubing blk - $0.49

    additional 12ga wiring (I under-estimated length needed for battery-backpack setup) - a few bucks at the local hardware store

    Fortunately for me, I have a bike stand and most of the necessary bike tools. So installation was pretty straight forward - remove chain, cranks, & bottom bracket, then finally install the BBS02 unit & wire everything up. Removal of equipment & installation of the BBS02 probably took me ~30min (not including wiring). For others, you may have to take your bike to your LBS to have them remove the cranks & bottom bracket. However, installation of the BBS02 should be doable with standard tools (mostly hex/allens) that you may already have in the garage.

    The part that took me the longest time was the wiring... mostly because I realized I didn't order enough cabling and had to run to different hardware & electronics stores to find the right gauge. Also, I'm pretty anal about dressing up the cables & heat-shrinking so it all lays flat against the frame & looks clean - so that took some time as well.

    I ended up not using the magnetic brake sensors for her hydraulic disc brakes. It's kind of gimmicky and looks really hokey when installed. I don't see a need for it as the motor stops when you stop pedaling anyways. I'm also glad I did not purchase the optional gear select sensor, which pauses the motor when it detects a gear-shift change. So far, shifting is smooth under power - no clunking or crunching when changing gears.

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    Driving the BBS02 is Luna Cycle's 52V, 13.5Ah Slim-line battery pack. It's made up of quality 18650 cells - supposedly the same Panasonic cells Tesla uses. This battery pack was designed to be mounted on a bike-mounted rear rack. The wife's x-small frame had no room to frame-mount the battery & adding a rear-rack would be a last resort as having dead weight sitting rearward w/ a high center of gravity will only affect handling of the bike on the trails. So instead, I opted to run the battery in my old Osprey Zealot hydration backpack. The battery weighs ~8lbs - so no different than when it's fully loaded with a spare tube, tools & 3L of water. However, after several test rides, I'm now looking to purchase Luna Cycle's Mighty Mini Cube battery and mount it in a saddle bag as done in this blog. The battery weighs ~3lbs and he can actually fit it in his pocket!

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    Initial testing of the bike on the streets, pedal-assist worked great. You have to pedal a good cadence for PAS to work - if your cadence is too low, PAS won't kick in. When you stop pedaling, the motor stops as well. The unit also shipped with a thumb-throttle (which I mounted upside-down for safety reasons). However, I felt the throttle applied way too much power and doesn't apply it gradually which results in instant wheelies - which scared the crap out of me the first few times. The throttle works more like an on-off switch rather than like a scooter accelerator - the wife & I didn't see a need for it, so I left it mounted but disconnected.

    When we actually went out for a hill climb on a trail that the wife usually dreads - one where she's making several (long) rest stops & ends up walking the bike up halfway to the top - she pedaled using Pedal Assist Level 1 all the way to the top with a big smile. She made a couple of short stops for water breaks and during these short stops I touched the motor to see how hot it was running (I haven't done the aquarium temp mod yet) but it was always just barely warm. She's really loving her 'new' ebike... & I am too since now we can now enjoy the ride(s) together.

    Last edited by cfanto; 01-19-2018, 07:38 AM.

    Good looking bike & build. Outstanding that your wife now enjoys biking with you, can't put a price on that.


      It's awesome to see the smile on her face at the top of the hill (or even during the climbs)... rather than that look of despair!

      I loaned out her bike to a buddy that was gonna bail on a planned ride due to some ankle pain. He had no problems or issues w/ his ankle while climbing some steep hills and now he & another one of our other riding buddies wants to get their bikes outfitted!


        Nice conversion. Where did you get the chain ring adapter?


          From ordered as part of the kit.

          I went online earlier & noticed they no longer include it as an option for the BBS02. You can still order it separately for $35.95 or $72.90 w/ the 34T RaceFace NarrowWide chainring... but it was nice when it was discounted when you purchased it with the motor as a kit.