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Gravity Bullseye Monster + BBSHD 100mm Build Report

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    Gravity Bullseye Monster + BBSHD 100mm Build Report

    I bought the BBSHD 100mm kit from Luna with the following components:

    100mm BBSHD
    48V Shark Panasonic 13.5ah Battery & Advanced 300W charger (they throw in the correct barrel connector cable for "free" with the kit)
    Stock 46T steel chainring
    C965 Display
    Univeral Thumb Throttle
    Bafang Handles with Built-in Ebrake cut off
    Luna wrench
    Programming Cable (reprogrammed using the Karl's Secret Sauce settings)

    and installed it all on a Gravity Bullseye Monster fat bike (a few years old, but it looks identical to the 2019 model here: http://www.bikesdirect.com/products/...ye-monster.htm)


    Overall, the installation couldn't have been much easier. One problem was that I either lost or never had the correct bottom bracket tool for this bike (Park Tool BBT-22 or BBT-32) and the bottom bracket cups were pretty nasty, as usual. Spending $19 for the Luna wrench seems like a waste but unless you already have a tool that can easily tighten the gray ring, it is basically a necessity.

    The only other issue was that the Shark battery holder wouldn't mount in the correct position using both of the down tube's water bottle bolts. I thought about how to deal with this for awhile and considered drilling a new boss higher up on the frame but then I remembered a Luna video that showed removing the plastic cover (https://www.youtube.com/watch?v=AKmrLkXVwHA) and drilling through the battery holder. This was a much better idea and it took about 5 minutes to mark, drill, and mount the battery using the existing bosses.

    The 100mm BBSHD fit perfectly with no spacers, although I used a couple of washers in between the motor and the bottom bracket plate. The "ugly and heavy" stock chainring is not as bad as described and I would definitely start off with it and only upgrade later if you have problems or want something fancier. It did drop the chain once, but I replaced the original chain with a new 8 speed rustbuster chain and it has been solid ever since. Finally, I might be extra dumb but the speed sensor made no sense at first - there are two plastic parts and the sensor slides into the other part, which is then zip tied to the frame, and a set screw is used to control how far the sensor slides out towards the spokes. Those two plastic parts got separated in the process of dumping out the parts so I was confused what this one weird looking plastic part was...

    I started off with the stock 750W settings, but after the initial testing, reprogrammed using Karl's Secret Sauce settings which are about 1000x more fun. PAS 3 or 5 makes this fat tire beast ride like a road bike and hitting the throttle on hills makes them effortless. The display (and 5 position controller) is perfectly fine and I like the thumb throttle, at least for using it as "boost". Brake levers are also fine and slightly nicer than that stock Tektro levers that came with the bike.

    Overall, I probably spent about 3 hours on the build from start to finish and knowing (now) how to correctly mount the battery would have probably saved 30-60 minutes. The bike is a total blast to ride and I already have three Christmas requests for their own ebikes...
    "I got it up to 30 MPH!"

    #2
    How were you able to mount without spacers? I just did a ltd and it required 6mm of drive side spacers to prevent pinching the chainstay. Is the non ltd different?

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      #3
      Originally posted by Msim View Post
      How were you able to mount without spacers? I just did a ltd and it required 6mm of drive side spacers to prevent pinching the chainstay. Is the non ltd different?
      It must be a different frame or I have an older model because there is a decent amount of clearance without any spacers.

      Chainring clearance

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