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BBSHD on a 2007 Trek Fuel EX9

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    BBSHD on a 2007 Trek Fuel EX9

    BBSHD on a 2007 Trek Fuel EX9

    05-16-2017, 05:08 PM

    This is my third Bafang BBSXX conversion. I did a 29er hardtail and a hybrid road bike with BBS02s. Both are really fun but I realized to get the best performance on the really steep fire roads and trails near where I live (Ojai CA), I needed a full suspension bike with very low gearing. I like doing 20+ mile rides over pretty steep terrain so I really wanted to be able to fit a 14S4P "Shark Pack" in the triangle. Also, I use a Shark Pack on my other bikes so I wanted to be able to swap batteries on all three bikes. I use a MiniCube in a under-seat bag too for really long rides.

    So my main criteria for donor bike were:
    1. Full Suspension
    2. Large frame triangle.
    3. Good chain line using small (i.e. non-offset) chainring.
    4. "Cheap" ($750 or less)

    I found most of the newer full suspension MTBs used press-fit bottom bracket shells. They can be adapted to work with the BBSXX but it was really hard to be sure the wider BB shell would allow the BBSHD gear housing to mount without producing a really lousy chainline on the granny gear. I didn't want to use an offset chainring because they have to be at least 42T. That would mean I'd need to use a really big granny gear. Feasible, but less common and usually much more expensive to set up.

    So I settled on an older (2007) Fuel EX9. It has a 68mm BSA BB shell and a chainstay design that allows the BBSHD gear housing to clear without needing shims.
    I would have preferred a 27.5" wheel but I couldn't seem to have that and also meet my other criteria. I figured I'd just use really big tires and hope for the best.

    Click image for larger version  Name:	IMG_3176.JPG Views:	1 Size:	426.9 KB ID:	35590Click image for larger version  Name:	IMG_3178.JPG Views:	1 Size:	446.7 KB ID:	35591
    Click image for larger version  Name:	IMG_3179.JPG Views:	1 Size:	447.5 KB ID:	35592

    The motor fit nicely. No shims needed at bottom bracket or triangle mounting plate. Downtube design allows motor housing to be rotated up with good ground clearance.

    As for the battery mounting, it was pretty straightforward. Lower end of the battery case needed to clear the rear shock it its full range of motion. And the upper end had to have room to slide forward to release. I wanted to use all three mounting holes on the cradle as well as securing the aluminum heat sink of the cradle to the downtube.
    (See Luna's video on Shark mounting: Click image for larger version  Name:	IMG_3181.JPG Views:	1 Size:	392.5 KB ID:	35593

    This meant adding 2 more Rivnuts.
    I used steel ones I got from Amazon: ( image for larger version  Name:	IMG_3184.JPG Views:	1 Size:	394.5 KB ID:	35594

    I'm too cheap to buy the actual Rivnut tool so I did it with the "two-wrench-two-nut" method.
    See video:

    Click image for larger version  Name:	IMG_3526.JPG Views:	1 Size:	400.8 KB ID:	35595

    And because I don't trust the little tabs on the SharkPack to hold up to off-road use, I also used elastic scuba-diving knife straps on it.

    All of that worked quite well. But the 30T Mighty Mini chainring and the 11-34T cassette, while really good offroad, left me "ghost pedaling" on the street at fairly low speed. I really wanted a broader range of, but not necessarily more, gear ratios. SRAM makes a really nice wide ratio cassette, derailleur, shifter and chain set up for eMTBs. But at $800, that just wasn't in the budget.

    So I tried a Sunrace CSM 980 11-40T cassette and a PreciAlps 36T chainring. (PreciAlps is pretty similar to Lekkie. Just more French. At the time I don't think Lekkie was out with their 36T yet). Had to add a derailleur hanger extension. I was a little amazed to find that it worked quite well on the bike stand. But under load I could never get the granny gears to stop the "clickety-clickety". Really was gonna need a newer derailleur to handle that big a cog. So I gave up on that.

    Then I had an idea. Maybe I could stack two front chainrings. Click image for larger version  Name:	IMG_3528.JPG Views:	1 Size:	455.5 KB ID:	35596Click image for larger version  Name:	IMG_3531.JPG Views:	2 Size:	384.3 KB ID:	35597

    I had to turn a new aluminum hub for the 36T PreciAlps chainring to provide the right offset. But it stacked nicely on top of the 30T Mighty Mini. In fact it prevents chain drops off the 30T. Haven't figured a way to modify the front derailleur to shift chainrings with it, but for now I just move the chain by hand when I leave the road and begin the trail. Key thing is to remember to Turn The Motor Off! Click image for larger version  Name:	IMG_3524.JPG Views:	1 Size:	470.5 KB ID:	35599
    Click image for larger version  Name:	IMG_3525.JPG Views:	1 Size:	474.1 KB ID:	35598

    So anyway, I'm really liking this bike. I'm adjusting to the 26" wheels. Got some 2.5" tires and run them tubeless at low pressure. Very compliant. Makes my hardtail feel like a WWII era Willy's Jeep.

    Came in at around $1800. (Already had the battery). Seems like a pretty good deal.

    Gotta admit though, I still wonder if some of the stuff Luna sells for $2500-$3000 might be significantly better. Their prices on KHS stuff in particular is pretty hard to beat.

    This was a top of the line bike. (10 years ago.) Good enough for me.