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  1. #1
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    how do I measure chainstay length?

    I've been measuring from the middle of the bottom bracket socket to the axel on the rear wheel...is that correct?

    the reason I ask is I'm after a new frame....according to that measurement system my junkyard roadbike has a chainstay length of around 450mm, which seems rather long.

  2. #2
    'Mizer Cats are INSANE Mentor58's Avatar
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    Yep, that's the way you measure it. That's long, but not out of the ballpark. Here the the lengths on my bikes. (measurements are center to center)
    Long Haul Trucker (Heavy Touring Frame) = 460
    Volpe (Light Touring, Cross, All Purpose Frame) = 425
    MotoBecane (Fast Road Frame) = 410

    Sounds like you have a touring frame, can you provide any more info?

    Hope this Helps

    Steve W
    *Surly LHT ... Slow and Steady, *Motobecane Century Pro ... Better than Me
    *Bianchi Volpe ... Well, just 'cuz , Fuji Track SS / Fixie ... Mustache bars and a big grin
    Rans F5
    Easy Racers Tour Easy
    * Now that I'm 'Bent, I will probably unload all but the Fixie.

  3. #3
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    I was always under the impression that the distance from the center of the bottom bracket to the center of the dropout measured parallel to the top tube was considered the actual chainstay length. If you're not measuring parallel to the top tube, then you're measuring the diagonal of a triangle, not the shorter, parallel-to-top-tube distance. Of course, I could be wrong...

  4. #4
    'Mizer Cats are INSANE Mentor58's Avatar
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    Quote Originally Posted by FarHorizon
    I was always under the impression that the distance from the center of the bottom bracket to the center of the dropout measured parallel to the top tube was considered the actual chainstay length. If you're not measuring parallel to the top tube, then you're measuring the diagonal of a triangle, not the shorter, parallel-to-top-tube distance. Of course, I could be wrong...
    I don't think that top tube angle has anything to do with it. If I have 2 bikes with identical rear triangles, but one has a sloped top tube (compact geometery), and the other has a traditional geometry, they both still have the same distance from center of BB to dropouts, therefore the same chain stay length. That is a simple straight line measurement, not dependent on any other factors.

    Just my .02

    Steve W
    *Surly LHT ... Slow and Steady, *Motobecane Century Pro ... Better than Me
    *Bianchi Volpe ... Well, just 'cuz , Fuji Track SS / Fixie ... Mustache bars and a big grin
    Rans F5
    Easy Racers Tour Easy
    * Now that I'm 'Bent, I will probably unload all but the Fixie.

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    It has a headtube sticker (not badge) that says "Tensor Cycles, Darlington, England". It's lugged, traditional quill stem thing and the original freewheel is 6 speeds. The front fork also has alot of rake. Not fancy by any means but yeah. It also says "Panther" along the downtube.

    450mm does seem to me to be very touring length...it has braze ons for rack and fenders, yet none for waterbottles, did they only become popular later?

  6. #6
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    Quote Originally Posted by Mentor58
    I don't think that top tube angle has anything to do with it. If I have 2 bikes with identical rear triangles, but one has a sloped top tube (compact geometery), and the other has a traditional geometry, they both still have the same distance from center of BB to dropouts, therefore the same chain stay length. That is a simple straight line measurement, not dependent on any other factors. Just my .02 Steve W
    The angle of the top-tube when viewed from the side isn't what I'm talking about. Both top tubes you mention are still in the center of the bike when viewed from above. Viewing from above is what I'm talking about.

    The chainstays, however, angle outward from the center of the bike when viewed from above. Different bikes have different outward-chain-stay angles, depending on:
    1. the rear axle width
    2. how close to the center of the bottom bracket the stays originate
    3. on the length of the stays themselves

    Two bikes with identically long stays (measured parallel to the stay) would have different bottom-bracket-to-dropout lengths when measured parallel to the center of the bike (the top-tube center).

    I think the "proper" way of measuring is parallel to the center, not parallel to the stay. But, as I said before, I could be wrong...

    PS: I've posted the question in the framebuilders' forum to get an "official" answer.

  7. #7
    'Mizer Cats are INSANE Mentor58's Avatar
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    Quote Originally Posted by FarHorizon
    The angle of the top-tube when viewed from the side isn't what I'm talking about. Both top tubes you mention are still in the center of the bike when viewed from above. Viewing from above is what I'm talking about.

    The chainstays, however, angle outward from the center of the bike when viewed from above. Different bikes have different outward-chain-stay angles, depending on:
    1. the rear axle width
    2. how close to the center of the bottom bracket the stays originate
    3. on the length of the stays themselves

    Two bikes with identically long stays (measured parallel to the stay) would have different bottom-bracket-to-dropout lengths when measured parallel to the center of the bike (the top-tube center).

    I think the "proper" way of measuring is parallel to the center, not parallel to the stay. But, as I said before, I could be wrong...

    PS: I've posted the question in the framebuilders' forum to get an "official" answer.
    CLICK... (sound of the light going on). Yes, I'd agree with you 100 percent now. I sure didn't mean to imply that you would lay the tape against the stays themselves, it would be a straight line measurement from the center of the dropout to the middle of the bottom bracket, parallel to the top tube as you described. I'm going to blame it on lack of coffee for my bonehead mistake.

    Looking forward to seeing what the framebuilders say....

    Steve W.
    *Surly LHT ... Slow and Steady, *Motobecane Century Pro ... Better than Me
    *Bianchi Volpe ... Well, just 'cuz , Fuji Track SS / Fixie ... Mustache bars and a big grin
    Rans F5
    Easy Racers Tour Easy
    * Now that I'm 'Bent, I will probably unload all but the Fixie.

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