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Thread: Thomson X2 Stem Breakage ???

  1. #61
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    Default Re: Thomson X2 Stem Breakage ???

    Quote Originally Posted by duende View Post
    +1. Also, what's odd to me is that I've used a single bolt Cinelli 1A stem for years no no slipping. Still do on my Eroica Ciocc ride.

    Go figure.

    I went through two of them, and they were practically the only bike components I've ever broken. The first one was installed with grease and no carbon paste, tightened to slightly under torque spec, it slipped slightly after about two months and when I went to tighten it, it already had a partial crack that would flex when tightening the bolt. The second one was installed with grease and with carbon paste. It stopped slipping in the stand at an even lower torque setting, and everything felt good. At three months, the face plate just shattered. Thomson honored both breakages. I only used the second X2 because, as pointed out above, the X2 uses quite a shorter stack height, and it meant that I couldn't swap to another stem with significantly greater stack height without replacing the fork. I ended up doing just that.

    The X2 doesn't have to have such an atypically short stack. It makes it a problem solver if you already cut your steer too short, but it also encourages you to cut your steer too low for any other stem. I hate it for that reason alone.

    The thing about the old Cinelli stems is that they were made from such a soft aluminum that they would stretch and bend and whatever else before they'd ever break. You rarely saw a 1-A break, just like you rarely saw an original 63, 64, 65, or 66 break. They'd bend easily but the alloy was soft enough that it was very forgiving of crashes and abuse. It was only when brittler alloys and heat treating showed up that stems and bars started breaking with this kind of frequency.

    I'm not sure with the X2 that it's simply a matter of being CNC'd. I agree that a forged stem can be very reliable and trustworthy, but the quality of CNC blanks (many of which are actually forged and then turned) has lessened any issue with those designs. I don't think the X2 went through that sophisticated a design analysis in the beginning, plus it was originally billed for its lighter weight. To make a stem lighter, stiffer, and also to save weight by decreasing the clamping height on the steer all requires that the stem be made from a very rigid alloy. Rigid doesn't have to be brittle, but it often is. I think this is partly a design flaw, partly a choice of metal. Regardless, I'm in the camp that won't use an X2 and recommends against them. The X4 is extremely durable, and on the track I'll recommend the X4 as the only worthy alternative to a stem like the Pro Vibe (which is massively overbuilt and a completely forged shaft and head).
    Lane DeCamp

  2. #62
    Join Date
    Jul 2008
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    Default Re: Thomson X2 Stem Breakage ???

    Quote Originally Posted by 11.4 View Post
    I went through two of them, and they were practically the only bike components I've ever broken. The first one was installed with grease and no carbon paste, tightened to slightly under torque spec, it slipped slightly after about two months and when I went to tighten it, it already had a partial crack that would flex when tightening the bolt. The second one was installed with grease and with carbon paste. It stopped slipping in the stand at an even lower torque setting, and everything felt good. At three months, the face plate just shattered. Thomson honored both breakages. I only used the second X2 because, as pointed out above, the X2 uses quite a shorter stack height, and it meant that I couldn't swap to another stem with significantly greater stack height without replacing the fork. I ended up doing just that.

    The X2 doesn't have to have such an atypically short stack. It makes it a problem solver if you already cut your steer too short, but it also encourages you to cut your steer too low for any other stem. I hate it for that reason alone.

    The thing about the old Cinelli stems is that they were made from such a soft aluminum that they would stretch and bend and whatever else before they'd ever break. You rarely saw a 1-A break, just like you rarely saw an original 63, 64, 65, or 66 break. They'd bend easily but the alloy was soft enough that it was very forgiving of crashes and abuse. It was only when brittler alloys and heat treating showed up that stems and bars started breaking with this kind of frequency.

    I'm not sure with the X2 that it's simply a matter of being CNC'd. I agree that a forged stem can be very reliable and trustworthy, but the quality of CNC blanks (many of which are actually forged and then turned) has lessened any issue with those designs. I don't think the X2 went through that sophisticated a design analysis in the beginning, plus it was originally billed for its lighter weight. To make a stem lighter, stiffer, and also to save weight by decreasing the clamping height on the steer all requires that the stem be made from a very rigid alloy. Rigid doesn't have to be brittle, but it often is. I think this is partly a design flaw, partly a choice of metal. Regardless, I'm in the camp that won't use an X2 and recommends against them. The X4 is extremely durable, and on the track I'll recommend the X4 as the only worthy alternative to a stem like the Pro Vibe (which is massively overbuilt and a completely forged shaft and head).
    Yes, use X2, be careful how you cut it or now your steerer is too short for a "normal" stem.

    The 10d is also worth about a 5mm spacer for 110 length. When I swapped from a X2 to a Fizik stem (7d) I took out a spacer.

    So now you have to have enough steer to accommodate a change in both the stack and the stem angle
     

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