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  1. #1
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    Should reach be measured from the middle of the headtube?

    As most of you will probably know reach is the horizontal distance from the bottom bracket to the top of the head tube.

    More and more manufacturers have adopted this as one of the key measurements of a bike's size and indeed it is much more suitable in that regard than seat tube length of effective top tube length.

    However there is one (small) problem with reach that many don't realize and that is that it is influenced by the length of the head tube. Bikes with a tall head tube will end up shorter in reach than another bike of the exact same length, while generally you would put your bars at the position you want and not where the head tube with installed stem and spacers dictates it to be.

    So that's why I would propose that reach would be measured from the middle of the head tube instead of the top of it. This way the length of the head tube does have influence on reach as it should have (since you can't position your bars completely independent from the top of the head tube either), but it doesn't have the misleading effect it has now.

    I feel defining reach from the middle of the head tube instead of the top will make bikes with different head tubes lengths much easier to compare. What do you guys think?


    PS, than again it could make it hard to compare bikes with large wheels (and short head tubes) to smaller wheeled bikes with longer ones as the larger wheel bike would than measure shorter.

  2. #2
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    Just use front center

    Reach is only useful to compare similar bikes - as you noted, the head tube length screws things up. Fork length and BB height do to, though.

    Just use front center. It tells you what you actually want to know - which is where the front wheel is compared to the rider. And it's comparable between any two bikes without any caveats (though if you're talking really long travel rigs you might want to take the measurement with a rider onboard/sag accounted for).

    -Walt
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  3. #3
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    No measurement can be taken in isolation to mean f-all for the bike's fit and handling.

  4. #4
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    Isn't this why there is a stack measurement?
    I got some bad ideas in my head.

  5. #5
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    And what does stack alone tell you?

  6. #6
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    Quote Originally Posted by Walt View Post
    Reach is only useful to compare similar bikes - as you noted, the head tube length screws things up. Fork length and BB height do to, though.

    Just use front center. It tells you what you actually want to know - which is where the front wheel is compared to the rider. And it's comparable between any two bikes without any caveats (though if you're talking really long travel rigs you might want to take the measurement with a rider onboard/sag accounted for).

    -Walt
    "Problem" is reach has become the single most used measurement used by bike media in reference to a bikes size.

    It's also makes it harder to decide between sizes. Front-centre is currently more suitable for that as you say.

  7. #7
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    But reach tells you where the center of the top of the headtube is right??
    So you have a base point for where your top cap/spacers/stem/bars fit.
    So the stack and reach shows where this point is relative to the bb.
    So its very usefull at comparing bikes. Head tube length will effect where that point is.

    If you measured to the middle of the head tube then that is alot more vague isn't it?

    Stack and reach give you an accurate way of telling how long/high the bars will be from the BB.
    Front centre does not give you this as the head tube angle will effect the reach.

  8. #8
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    Quote Originally Posted by yamaha46 View Post
    But reach tells you where the center of the top of the headtube is right??
    So you have a base point for where your top cap/spacers/stem/bars fit.
    So the stack and reach shows where this point is relative to the bb.
    So its very usefull at comparing bikes. Head tube length will effect where that point is.

    If you measured to the middle of the head tube then that is alot more vague isn't it?

    Stack and reach give you an accurate way of telling how long/high the bars will be from the BB.
    Front centre does not give you this as the head tube angle will effect the reach.
    Agree

    Eric
    If I don't make an attempt, how will I know if it will work?

  9. #9
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    With front center as the guiding measurement, if I swap my bike's 45mm rake fork for a 65mm rake fork, is the frame suddenly too big for me?

  10. #10
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    If you increase the rake by 20mm, you reduce the trail by something close to 15mm, which is quite a bit. What it will likely do, all other things being equal, is that the steering response will be much quicker - more twitchy. But it will have no other effect on the bike's fit.

  11. #11
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    I think thats seat_boy's point. Fit is not effected by front center.

    Keep the same reach and stack and change the rake/head angle/fork etc.. and the bike fit does not change, the bars are in the same place, but the front center changes.

    Fit is where the 3 contact points are BARS / SADDLE / PEDALS.
    So reach stack and seat tube angle give you most of what you need for fit of a frame.
    Then you can work out if you can get it where you want with crank length, stem, spacers, bar, seatpost etc..

    Where the wheels are in relation is not to do with bike fit. Handling and ride yes.

  12. #12
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    Fit is something you deal with after you figure out the wheel positioning, though. Just use a shorter/longer stem or a post with more/less setback once you have the wheel position you want.

    I mean, guys, fit is easy. It's basically 3 points in space. You can "fit" on an XL even when you're only 5'8" or something if you use the right components. How the fit interacts with the wheel positioning is what we care about, so you might as well start with the wheels and work your way back.

    And yes, the extra 20mm of offset might make you not like riding the bike - front wheel too far in front of you (or not far enough) has some obvious consequences for handling. Or it might be great. But using just the "fit" via stack/reach/etc you would never think to question that, because they only work for bikes with near-identical (ie road, which is their heritage) geometry.

    -Walt
    Waltworks Custom Bicycles
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  13. #13
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    Perhaps it would be a good idea to split two things up; handlebar start position through reach and stack (keeping the reach the same as it is now, top of the head tube) and frame length (horz. distance BB to middle of the head tube @ a given A-C).

    That way you can still easily judge how to position your handlebar across bikes with the spacers and stem same as now but it will become easier to compare the length of a frame, between sizes or brands by eliminating most of the headtube length influence like now with reach.

    Might sound over the top to list both, but many bike firms still list actually and eff. toptube length with both having little practical meaning to the end consumer. Better to get rid of those completely and list reach and frame length instead.

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