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  • Lowest bottom bracket on a rigid 29er?
  • Premier Icon legometeorology
    Free Member

    What’s the largest BB drop you’ve run on a rigid 29er?

    Asking as I’ve rebuilt my Pipedream Sirius (the older 4G model) from a half-plus single speed thing into a fast XC bike, and am thinking of continuing in that direction with some Exotic forks. But I don’t really want the really long 490mm ones and would rather the 465mm

    My BB drop is already nearly 80mm though (with 483mm forks), so a fair bit larger than most stock rigid 29ers like the Kona Unit, Surly KM, and the deceased Pinnacle Ramin. Only the Bombtack Beyond+ is close at 78mm drop, and that’s with 650b+

    The bike as it was before the rebuild

    Premier Icon sillyoldman
    Full Member

    A 78mm drop on 650+ will result in a lower BB than an 80mm drop on 29”.

    Your BB drop will increase by around 8mm for that fork length difference I’d imagine, so without knowing how close to 80 you’re at presently, how long your cranks are and how often you hit pedals on trail features, it’s hard to say whether it would be too much or not. Down to you really. Doesn’t sound crazy to me on a rigid bike where BB height doesn’t change (other than due to tyre deformation).

    That said, I specced 74mm drop on a rigid SS 29 frame I’m impatiently waiting on.

    Premier Icon jameso
    Full Member

    Not sure how low the BB is on my Jones but it’s lower than any other rigid 29er I’ve ridden or know of when the EBB is set at 6pm. I think it’s about 85mm? You’ll end up about there or a bit lower.
    I get the odd pedal strike SSing on 175s, few on 170s – had more to begin with and then adapted to it. I ride in the south though, not somewhere rocky. Byway ruts can still be a PITA if the BB is too low. Gravel bike can be a PITA there whereas the Jones mostly isn’t.

    Premier Icon legometeorology
    Free Member

    My BB drop seems to be at 76-78mm right now, crank length 170mm

    Works well until the rutted stuff… But that sort of thing is fairly rare for me nowadays

    Ya the Bombtrack BB is crazy low given it’s a 650b+

    I didn’t think about the Jones, looks like they are at 82mm, so pretty similar to where I’d be with 465mm forks, although the Jones is running 29+, which raises the BB a good few mm compared to my 2.3″ 29ers

    Premier Icon DanW
    Free Member

    Not sure how it translates to the rigid fork length, but most XC hardtails with a ~506mm AC height 100mm suspension for are around 60mm. My steel rigid frame is 58mm BB drop (506mm AC height fork) as that mimicked my old Trek Procaliber. Make of that what you will! 🙂

    Premier Icon jameso
    Full Member

    I didn’t think about the Jones, looks like they are at 82mm, so pretty similar to where I’d be with 465mm forks, although the Jones is running 29+

    Mine’s the old geo 29er, with 2.3s om most of the time. FWIW.

    Premier Icon sandwicheater
    Full Member

    80mm on my Stiff Squatch.

    Built from spares and at the moment 175mm cranks make life fun in some stuff.

    Will get some 165mm cranks shortly.

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