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stem lenght

vision267vision267 Posts: 149
edited September 2009 in Road beginners
Silly question but hear goes currently have a 110mm stem on my bike but it feels too cramped.Would a 120mm or even a 130mm throw out the handleing that what my local bike shop said,and strongly adviced against it?The oringal stem lenght of the bike is 100mm but i then got a compact handle bar.To compensate I got a 110mm stem but it still seems too cramped.Now I am a little fitter I feel I need a little more of a streach dont want to put on the handle bar that came with the bike?

Posts

  • gkerr4gkerr4 Posts: 3,408
    130mm would be about the limit I think - that said, have a look at some of the pro's bike - tom boonen in particular uses a massive stem - it must be about 150mm!

    Get one and try it - it' can't be that bad and you won;t know any other way - just find a bit of a cheapo - ribble were selling off end-of-line ITM stems a while back, they might have some left.
  • Last time I saw Big Tom he crashing in the tour de France,I think I saw him crash 4 times.No only kidding trip to the local tomorrow thanks for the reply
  • N4PALMN4PALM Posts: 240
    I believe a common way to set up is to have the centreline of the front of your bar drops line with the front hub. If you are in front of the hub this will slow your steering and if behind this will quicken your steering.

    This will depend on wether you liek twitchy handling or stability.

    As you have a compact bar I'd imagine you are still behind the hub. The risk of going too far in front of the hub is that too much weight will be on the front wheel that is all.
  • redddraggonredddraggon Posts: 10,862
    120mm stems are fine even on very small frames.
    I like bikes...

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  • Thanks guys,I just dont know what that man in the shop was going on about saying it was very dangerous. :wink:
  • Your LBS know nothing. A long stem will make you look like a pro which in turn will make you go faster :)
    Cannondale Supersix / CAAD9 / Boardman 9.0 / Benotto 3000
  • Thanks oscarbudgie got a 120mm stem just came back from a short ride.It feels fantastic wish I done it ages ago spot on advice on this site very greatful
  • Got tje stem from a different bike shop
  • im running a 110 at the moment and just picked this up cheaply to give a longer one a try, bit of a bargin! more so if I offload my old stem for a fiver!!!

    http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 516wt_1165
  • kfinlaykfinlay Posts: 763
    Sorry to hijack this thread a little but can anyone tell me how to measure the stem length - not sure where to measure from and to? If you get what I mean. Is it from the centre of the handlebar hole to the centre of the steerer hole?
    :?

    TIA
    Kev

    Summer Bike: Colnago C60
    Winter Bike: Vitus Alios
    MTB: 1997 GT Karakorum
  • gkerr4gkerr4 Posts: 3,408
    kfinlay wrote:
    Sorry to hijack this thread a little but can anyone tell me how to measure the stem length - not sure where to measure from and to? If you get what I mean. Is it from the centre of the handlebar hole to the centre of the steerer hole?
    :?

    TIA

    yes - thats exactly it - centre to centre.
  • neebneeb Posts: 4,430
    Sorry to hijack this thread a little but can anyone tell me how to measure the stem length - not sure where to measure from and to? If you get what I mean. Is it from the centre of the handlebar hole to the centre of the steerer hole?
    Confused

    TIA

    yes - thats exactly it - centre to centre.
    Beware however, it is quite difficult to do when the stem is on the bike. You really need to measure the side of the stem at the midpoint. Because the stem is angled, if you measure from the top you will get a longer measurement, and if you measure from the bottom you will get a shorter one. This can make a difference of about half a centimeter. And it goes without saying, if you have spacers on top of the stem and you measure from the center of the top cap to the center of the bars, the measurement will be even longer!
  • neebneeb Posts: 4,430
    Just to clarify:
    stem.jpg
  • kfinlaykfinlay Posts: 763
    Thanks for that guys, just looking to fine tune my riding position bit by bit and try to take time to assess each change before going onto the next, not that I think there is much I need to do as I find my bike very good so far.
    Kev

    Summer Bike: Colnago C60
    Winter Bike: Vitus Alios
    MTB: 1997 GT Karakorum
  • cjwcjw Posts: 1,889
    neeb wrote:
    Sorry to hijack this thread a little but can anyone tell me how to measure the stem length - not sure where to measure from and to? If you get what I mean. Is it from the centre of the handlebar hole to the centre of the steerer hole?
    Confused

    TIA

    yes - thats exactly it - centre to centre.
    Beware however, it is quite difficult to do when the stem is on the bike. You really need to measure the side of the stem at the midpoint. Because the stem is angled, if you measure from the top you will get a longer measurement, and if you measure from the bottom you will get a shorter one. This can make a difference of about half a centimeter. And it goes without saying, if you have spacers on top of the stem and you measure from the center of the top cap to the center of the bars, the measurement will be even longer!

    Don't worry about that, it's a very small difference.

    For a 6 degree stema 120mm stem would measure as 119.34 (cos 6 = 0.9945)
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    Focus Izalco Team
  • neebneeb Posts: 4,430
    Don't worry about that, it's a very small difference.

    For a 6 degree stema 120mm stem would measure as 119.34 (cos 6 = 0.9945)
    I think you're wrong.

    You're failing to take account of the stack height of the stem.

    Taking a 110mm stem measured from the side center to center, if you are measuring from the top you are finding the other long side of a triangle where the short side is (say) 15mm (half of a 30mm stack height), and the angle between the short side and the known long side is 96 degrees.

    x squared = 15 squared + 110 squared - 2 x 15 x 110 x cos 96
    x= 112.56.

    Interestingly, the error measured from the bottom seems to be less:

    y squared = 15 squared + 110 squared - 2 x 15 x 110 x cos 84
    y= 109.45

    I didn't know that until you forced me to work it out... Actually I still don't get it because I'm sure when i measure it the error from the top is about the same as from the bottom, and not as much as 1.5cm. Maybe there's an error in my working out.

    I generally prefer to take the empirical approach and just use a ruler.. :wink:
  • cjwcjw Posts: 1,889
    Isn't the stack height constant though from one stem to the next. I was considering the case of simply measuring fixing point to fixing point of the stem?

    So if you replace a 120mm stem with a 100mm stem you are changing the reach by 20mm regardles of stack heigh (as that stays the same).
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    Focus Izalco Team
  • neebneeb Posts: 4,430
    So if you replace a 120mm stem with a 100mm stem you are changing the reach by 20mm regardles of stack heigh (as that stays the same).
    Yes, but if you are trying to measure your stem to find out how long it is, you will get misleading results if you measure from the top. You are right that if you know your stem length already, it's not a problem, a 1cm longer stem will increase your reach by 1cm. But if you don't know your stem length and want to know what size of stem to buy to get the right fit, you need to measure your current one. The error measured from the top is potentially enough so that you could think you have a stem of of the next size up, and end up buying a replacement of the same size.. :)

    I'm just waiting for someone to make the obvious obscene analogy... :lol:
  • cjwcjw Posts: 1,889
    Ok... got you now.

    Just checked my stem and, by peering at the side very very carefully I can work out the length pretty acurately, just by eye, with no ruler, calipers or micrometer.......it's written there :lol:

    Of course ..... regardless of what the ruler says, it's much more than 6 inches :oops:
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    Scott Scale 10
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