ITM Stem Bolt - failure..sort of'

yenrodcp
yenrodcp Posts: 9,991
edited June 2007 in Workshop
http://www.fisheroutdoor.co.uk/public/i ... vmi9j6se44


3wks back I boought from Halfords some bolts same length as there was in the stem when bought except the they where chromed but goldish and not silver if you know what I mean.

Anyhow the ones supplied where old and discoloured and the section where the key went in was widened so new ones fitted the bill.

Anyhow was on a ride before and decided to adjust the the bars up a touch as you do except upon tightening the upper bolt went bang, oh ****, I thought - if its snapped from the head of the bolt then maybe the friendly man from the RAC parked up and messing around in his van will be able to hell but no the thread had 'gone' in the stem. So I rode it home taking it easy.

Got back and threw a longer bolt in the stem and it worked !

So the moral of this story is I believe that ITM supply their stems with too short bolts top affix the stems !!!

[:(!]

[;)] 'tuono nel mio cuore...[:)]
[;)] \'tuono nel mio cuore...[:)]

Comments

  • gbb
    gbb Posts: 1,240
    I assume youre saying the thread stripped out in the alloy.
    I also assume youre taking about the handlebar clamps...Looking at the pic of the stem..you only have TWO bolts to clamp the bars....and the threaded section doesnt look as though its that deep.
    Just peeked at my Bianchi stem...the bars are clamped by four bolts, not two...and each bolt goes a full 10mm into the threaded section of the stem...there is even room for longer bolts.

    Sadly...the design looks a bit deficient from a security or strength point of view.

    Go on then...tell me its the bolts that clamp the stem to the fork tube...[:D][:D][:o)]
    Chill out, fer Christsakes....
    Chill out, fer Christsakes....
  • yenrodcp
    yenrodcp Posts: 9,991
    Yeah, still giving me probs hence: http://www.cyclingplus.co.uk/forum/topi ... _ID=134509

    But I'm just trying ot find out if a 26.0mm clamp size will take the bars I have (itmpro260's) [url][/url] which are supposedly 25.8mm [?]


    <blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by gbb</i>

    I assume youre saying the thread stripped out in the alloy.
    I also assume youre taking about the handlebar clamps...Looking at the pic of the stem..you only have TWO bolts to clamp the bars....and the threaded section doesnt look as though its that deep.
    Just peeked at my Bianchi stem...the bars are clamped by four bolts, not two...and each bolt goes a full 10mm into the threaded section of the stem...there is even room for longer bolts.

    Sadly...the design looks a bit deficient from a security or strength point of view.

    Go on then...tell me its the bolts that clamp the stem to the fork tube...[:D][:D][:o)]
    Chill out, fer Christsakes....
    <hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

    [;)] 'tuono nel mio cuore...[:)]
    [;)] \'tuono nel mio cuore...[:)]
  • stevec205gti
    stevec205gti Posts: 366
    There are design rules for the number of threads/length of engagement (and I know thechnically there's only one continuous thread!) for a given bolt diameter - I would have thought it is more likely that the bolts have been overtightened rather than the whole system designed wrong, especially if you've been tightening things enough to round off the hex heads of the bolts in the first place.

    Burning brake blocks - the smell of fear
    Has the head wind picked up or the tail wind dropped off???
  • monty_dogcp
    monty_dogcp Posts: 382
    You only really need about three turns of thread to take the 'full load' so generally in engineering 6 turns is the accepted minimum. The reason is that there are tolerance or clearances between the parts and effectively the parts only mate effectively over the three turns - if there were zero tolerance, the friction would be excessive and the screws wouldn't turn. Sounds to me that the bolt has been over-tightened or that they weren't tightened evenly and so one bolt has take the whole clamping load - this is one of the reasons why a torque wrench is a good idea when fitting multiple-bolt stem clamps. Fitting 25.8 bars with a 26.0mm stem has been accepted practise for years - 0.2mm clearance is an acceptable engineering 'fit'
  • Lucky Luke
    Lucky Luke Posts: 402
    <blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by yenrod</i>

    Yeah, still giving me probs hence: http://www.cyclingplus.co.uk/forum/topi ... _ID=134509

    But I'm just trying ot find out if a 26.0mm clamp size will take the bars I have (itmpro260's) [url][/url] which are supposedly 25.8mm [?]


    <blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by gbb</i>

    I assume youre saying the thread stripped out in the alloy.
    I also assume youre taking about the handlebar clamps...Looking at the pic of the stem..you only have TWO bolts to clamp the bars....and the threaded section doesnt look as though its that deep.
    Just peeked at my Bianchi stem...the bars are clamped by four bolts, not two...and each bolt goes a full 10mm into the threaded section of the stem...there is even room for longer bolts.

    Sadly...the design looks a bit deficient from a security or strength point of view.

    Go on then...tell me its the bolts that clamp the stem to the fork tube...[:D][:D][:o)]
    Chill out, fer Christsakes....
    <hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

    [;)] 'tuono nel mio cuore...[:)]
    <hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">



    Which stem are you using ? I use these exact same bars with an ITM forged lite luxe stem , about œ20 for the stem if I remember , no probs .

    Luke
    Luke

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