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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:

    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 ( 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...

    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?


      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