Viewing 10 posts - 1 through 10 (of 10 total)
  • Bike geometry question
  • jamesgarbett
    Free Member

    In simple terms, could someone explain to me the difference in handling of raising the bars through a longer fork vs. raising the bars through running more spacers under the stem please?

    Say 140mm travel vs. 120mm travel with an extra 20mm of spacers under the stem (I appreciate that sag might be different at the two travel lengths but I’m ignoring that for now)

    ahwiles
    Free Member

    Hi James!

    a longer fork will slacken the head angle. The commonly quoted rule-of-thumb is 1-ish degree per inch-ish raised.

    this will (roughly), make descending easier, climbing more difficult.

    (but we’re only talking a small amount here).

    a longer fork will also raise the BB a touch, which might help with crank clearance…

    jamesgarbett
    Free Member

    OK thanks but doesn’t raising the bars through higher rise/more spacers also make descending easier and climbing harder?

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    ahwiles
    Free Member

    in my experience, raising the handlebars makes everything more difficult. The only reason i’ve ever done it is for comfort / fit reasons.

    most Dh’ers are now trying everything they can to lower their handlebars…

    (internal headsets, flat-bars, top-crown-over-the-stem)

    mugsys_m8
    Full Member

    How will a longer fork slacken the head angle?
    or is there is a diff between head angle and headtube angle?

    Diff between the two option James questions, is with the spacers, won’t it raise the handlebars vertically, therefore height diff between saddle and bars is changed without raising the front of the frame…err is this where head angles rather than head tube angles come in to play? I’m interested, i’m starting to think about frame geomteries these days.

    GaryLake
    Free Member

    How will a longer fork slacken the head angle?

    As you raise the headtube of the bike from the fork, the bike rotates around the rear wheel as it’s axis. Thus the headtube angle gets slacker.

    mugsys_m8
    Full Member

    D’oh. of course. The headtube stays at the same angle to the top tube, but the whole thing rotates around the rear axle. Cheers

    Bimbler
    Free Member

    Different question – is there a difference between raising handlebars with spacers or via higher rise bars?

    ahwiles
    Free Member

    one is more socially acceptable than the other…

    (although if you’ve got a trimmed to fit steerer-tube, you might not have much choice)

    jamesgarbett
    Free Member

    Just aesthetics Bimbler

Viewing 10 posts - 1 through 10 (of 10 total)

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