Taller head tube or reversed stem, which is safer?

Discussion in 'Cycling Equipment' started by mikael17128, Jun 25, 2007.

  1. mikael17128

    mikael17128 New Member

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    I want more comfort for longer rides so I reversed my stem to the upside. This strikes me as something that will make the bike less stable / manuverable. My question is whether there is any material difference between reversing the stem (as I have done) and buying a new frame that has a taller head tube of exactly the same height difference as my flipped stem?



    For whatever reason I feel the taller head tube would be more stable / safe. Any of you engineers care to prove me wrong?



    Mike Wesler
     
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  2. gclark8

    gclark8 New Member

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    Just use a stem riser, black or silver.

    I fit them to Giant CRXs almost weekly. ;)
     
  3. alienator

    alienator Well-Known Member

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    Your stem has zero to do with the bike's stability. Weight distribution, frame geometry, and fork geometry are what contribute to stability. By flipping the stem you've done nothing to change any of that. Sure, weight distribution might change some miniscule amount, but it won't be anything you'll notice....ever.
     
  4. mikael17128

    mikael17128 New Member

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    Thanks for the input...So your saying that whether my stem is rises or my head tube is taller, the stability of the bike will be the same? It's all about weight distribution? I hope you're right, I don't want to buy another frame!

    I disagree with your hypothesis about 'miniscule' changes in weight distribution. I once flipped the stem on an already oversized bike and it became downright dangerous (IMO).

    Mike
     
  5. alienator

    alienator Well-Known Member

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    Well, believe what you will, but if you do the math, the change in the bike/rider system's CG as a result of flipping a stem is so very small....very, very small. If the bike became downright dangerous, then something else happened. It was nothing to do with the stem's orientation. Full stop.
     
  6. 1id10t

    1id10t New Member

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    I've flipped my stem on several ocassions with different bikes and haven't noticed a difference in handling. Many stems these days are reversible; I don't imagine the manufacturers would market it that way if they thought it would be dangerous.
     
  7. gclark8

    gclark8 New Member

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    I convert and build flat bar bikes, the stem makes more difference than changing the seat post!

    I use a set of bathroom scales under the front wheel for all weight calculations. NO ONE gets out of here with less than 35% of the gross weight on the front wheel!

    I found if you go higher with the steerer tube you have to go longer with the stem.

    The Stem Riser with the original stem, droped, or a longer adjustable stem, may be the answer.
     
  8. artemidorus

    artemidorus New Member

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    George, could that be because changing the seat post makes little difference, rather than because the stem makes a big difference? Are you talking up/down or fore/aft with the seat?
    For the OP, I would say, try the bike with the flipped stem and keep it if you think it is comfortable and stable. You'll notice any loss of stability, but I doubt that there will be one.
     
  9. mikael17128

    mikael17128 New Member

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    I should know better to argue with an alias called "alienator" but I feel this needs to be addressed. YOU ARE WRONG, period. I just rode my bike with the flipped stem and didn’t notice all that much difference. There was, however, a difference. It was not huge, it was not very very slight as you claim it should be; there was a moderately different ride quality. This was on an undersized bike, so the flipped stem returned me to a more normalized center of gravity. When I flipped the stem on my former oversized bike it became, as I have said, downright dangerous. I noted this danger while coming down a mountain at 35 miles per hour. And no, it was not because I was going so fast or the road quality was poor. It was because my center of gravity was too high.



    I will reply to your postings no further.



    MRW



     
  10. alienator

    alienator Well-Known Member

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    What a dick! Did your mommy not love you?

    FWIW, I did not piss in your Cheerios. I gave you objective, factual answers.

    Since we're talking about objectivity, it's important to point out how bad your little "experiment" was. It proved nothing, other than your too stupid to actually do a valuable test.

    I have--as have tens of thousands, if not more, of other cyclists--have flipped stems without changing stability one iota. Of course, that's because stem angle has virtually dick to do with stability. Given the tone of your response, I think it's safe to say that you wouldn't come close to understanding a scientific or mathematical answer, so suffice it to say that your knowledge of bike stability is as inadequate, at least, as your ability to read tone in a forum post.

    Of course, the makers of stems and bikes know that flipping a stem does sod all to change stability, but that doesn't mean a dolt like you does.

    Piss off, princess.
     
  11. thomas_cho

    thomas_cho New Member

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    Seems like you have an oversized and an undersized bike. Perhaps a proper fitting bike might resolve whatever problems you have.
     
  12. hd reynolds

    hd reynolds New Member

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    Regardless on the issue on stability, an A-Head type system with the stem clamp as near as possible to the upper headset is safer since this puts less strain on the steerer tube in this area where it is most prone to failure (failure like Hincapie's crash at paris-roubaix).
     
  13. kdelong

    kdelong Well-Known Member

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    Just tried a ride with mine reversed and the only difference was that I was not used to the slightly lower riding position. I did feel any hint of danger though, and no loss of stability but then I'm pretty unstable as it is anyway:D .
     
  14. gclark8

    gclark8 New Member

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    HI Mike,

    I would like more information before giving a specific answer:
    What exacty is the bike, pix please?
    Post a link to the bike's Geometry, please.
    What size is the bike?
    How are you set up, seat position, seat height, stem length, crank length, pedal type?
    Pedaling style, lo or hi cadence, heel or toe down?
    Your height?
    Your weight?
    Your Age?

    All this will help in getting back on topic and giving you an informed answer. ;) (see also set up pix in Post 7 above)
     
  15. gclark8

    gclark8 New Member

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    I am referring to the fore/aft movement of the C of G of the bike. An extreme comparison is aTT bike 50/50 and a Ladies Comfort Bike 70/30.

    If you follow the logic of the previous arguements, then all riders must be on the same (small) size bike, to keep the weight low. :eek:
    (This week I'll ride "Little Jackie's" 24" Wheel Huffy)
     
  16. mikael17128

    mikael17128 New Member

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    George, here are my specifics…



    Bike: 2007 TREK Madone 5.9 (58cm).

    Geometry link: http://www2.trekbikes.com/bikes/bike.php?bikeid=1476000&f=1

    Set-up:

    - Bontrager 5mm setback seatpost

    - Sella Italia Prolink light saddle (set mid rail)

    - Stem: Inverted Zipp 145 stem with no spacers

    - Bars: Zipp contour (46 cm outside to outside)

    - High cadence (mid foot)

    - 6’0”, 170, 40 years



    I tested the bars again today. Found the new geometry with the flipped stem to be much more comfortable for the hands without too much of a sacrifice in safety. My question is whether I should buy one of the newer Madone frames with the taller head tubes? The way my bike is handling with the flipped stem I feel I have probably already answered my own question, ie. no (not worth the $$$).



    However, this still leaves the original question unanswered: Would a new 58cm “performance” Madone with a 3cm taller head tube and a downward angled stem be safer than my model with a flipped stem?



    Mike

     
  17. gclark8

    gclark8 New Member

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    Quick questions, what length stem? C-C.
    Crank length?
     
  18. CAMPYBOB

    CAMPYBOB Well-Known Member

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    The Zipp 145 stem has a 10 degree angle. The height change for reversing the stem would be approximately 1.72" (44mm) for a 120mm reach example. Approximately 1.57" (40mm) for a 110mm example.

    I can not see raising or lowering the torso by those amounts to cause the bicycle to somehow become "dangerous" or unsafe. The change in CG would be pretty small...certainly much less changed than riding while sitting up or while in a deep crouch or going nose-down/ass-up in a sprint.

    You state that the current setup has no spacers. It is perfectly safe to ride the bike with a 30mm stack of spacers under the stem and the 30mm maximum spacer dimension is limited by the safety of the leverage point of the stem on the steerer tube. Since you are not changing the leverage point of the stem on the steerer tube, you are not inducing an unsafe condition there.
     
  19. mikael17128

    mikael17128 New Member

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    110mm stem

    175mm cranks

    Looks like the other poster has determined that there is a 4cm difference in height.

     
  20. gclark8

    gclark8 New Member

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    I agree with Bob.

    Thank you for the response, we are now playing with a full deck.

    Was the bike purchased as a result of a professional fitting service and were you fitted to the bike at the time of purchase?

    If yes, go back to them, it may not be the right bike for you. The steerer tube is quite steep, the wheel base short, the chainstay short, and with the widely spaced low spoke count wheels, it would be a twitchy bike to ride anyway.

    I could many some suggestions as to better fit, but won't as I now believe it is the wrong bike for your purpose.
     
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