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measurement of handlebar stem

Discussion in 'Bicycle Mechanics and Repairs' started by alecstilleyedye, 12 Apr 2008.

  1. alecstilleyedye

    alecstilleyedye nothing in moderation Staff Member

    between which two points do i measure the handlebar stem to ascertain its length (so i can order a new one the same length).

    cheers in advance if anyone knows.
     
  2. Smokin Joe

    Smokin Joe Legendary Member

    Centre of steerer to centre of bars.
     
  3. Dave5N

    Dave5N Über Member

    Alex - centre to centre.
     
  4. Foghat

    Foghat Veteran

    If you're really particular about the dimensions of your bikes and geometry of your set-up, then bear in mind:
    • one manufacturer's 130mm (or whatever) may not be exactly the same as another's
    • oversize bars are about 6mm larger in diameter than 'ordinary' bars, so the centreline of the oversize bars will be 3mm further away, increasing reach by the same amount
    Maybe this won't concern you, but I have all my bikes set up to 1-2mm tolerance in the critical dimensions; this is because I notice the difference otherwise, and don't feel right if they're out.
     
  5. Shirley a centre to centre measurement is a centre to centre measurement irrespective of the diameter of bar or steerer.
     
  6. Foghat

    Foghat Veteran

    Yes, that's true. But manufacturers' centre-centre measurements are more nominal than precise, so they can't be trusted (certainly not between manufacturers, and not even between different models of stem by the same manufacturer) and should be checked manually....if accuracy is important to you.

    The point I was really making is that when measuring the critical horizontal centre-of-BB to bars dimension (assuming saddle is already correctly positioned behind BB), it is far easier to do it from the front of saddle to the rear of the bars at the centre next to the stem with the wheel dead straight. When doing this, one should factor in the fact that oversize bars' centrelines are 3mm further away than 26.0mm bars.
     
  7. Smokin Joe

    Smokin Joe Legendary Member

    I don't get that.

    The centre line will be exactly the same distance from the tip of the saddle no matter what the diameter of the bars.
     
  8. Foghat

    Foghat Veteran

    It's all to do with how one practically makes the measurements.

    As it's far easier to measure the distance-to-bars dimension by using the end of the tape abutting the rear of the bars, and the flat of the tape to visually line up the front of the saddle with a millimetre increment on the tape, one needs to be aware of the additional 3mm on oversize bars.

    You could use the tape the other way round, or try the end of the tape where you think the centre of the bars is, but estimating by eye where the centre of the bars is is harder, and in the second instance it's difficult to keep both hands exactly in place when looking closely at one hand.

    As most stems seem to be available in 10mm increments, those 3mm can be quite important in attaining the right reach.
     
  9. briank

    briank New Member

    Hold up, Joe

    Distance from tip of saddle to centreline of bars=dist from tip of saddle to reasmost edge of bars + radius of handlebar tubing

    Since O/S bars are about 6mm greater diameter than 'standard' ones, the radius is 3mm greater so the centreline is 3mm further from the tip of the saddle.

    Yes?
     
  10. Smokin Joe

    Smokin Joe Legendary Member

    Fcuk me, this is getting complicated.

    The distance from the tip of the saddle to the centreline of the bars will be the same whether the bars are 1/4" in diameter or two foot.

    Think about it.
     
  11. OP
    OP
    alecstilleyedye

    alecstilleyedye nothing in moderation Staff Member

    i found that, after redoing the brake cables (and hence redoing the bar tape), i got the shifters in a more comfortable position, so i'm putting the new stem on hold.

    i'll bear all the advice in mind though. cheers :angry:
     
  12. 02GF74

    02GF74 Über Member

    centre to centre. regardless of saddle diameter, shifter position, lottery numbers, bar diameter, weather outside, number of wasps in your lager .......etc
     
  13. Dave5N

    Dave5N Über Member

    swoti sed :biggrin: