stem fatigue and lifespan?- Mtbr.com
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  1. #1
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    stem fatigue and lifespan?

    In regard to fatigue, how long do you use your stem until you replace it? No hypothetical answers please. I'm asking for those that have used a stem so long that they decided to toss it out of concern.
    I've been running the same old Chromag HiFi since 2012 for thousands of miles in all kinds of conditions and it's now the only thing to have remained through 5 different bike builds. At what point should I consider replacing it? I've used a torque wrench every time I've installed it. But it's been crashed too many times to remember (literally! concussions!) and there have been a few rough edges that I've filed.
    I recently threw a handlebar in the trash because I had used it for 4,500 miles of rough rigid bikepacking and didn't want to take chances with fatigued metal on my next longish distance outing.

    Where do you strike a balance in terms of getting a stem that you want to last for years without getting some super heavy block?

  2. #2
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    I've got a Bontrager stem that is probably 20 years old and saw heavy use its first 10 years, and intermittent use since. It is very light stem, 120mm, that took a sound thrashing and still seems to be in good shape. Never really thought about it fatiguing out - maybe I should.

  3. #3
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    ^^^ yeah. Sounds like a legit concern, but I've never been aware of anybody being concerned about it...so I did the natural thing, googled it, and found this:

    https://www.sheldonbrown.com/rinard/stemtesting.htm

    Not totally relevant, but interesting.

    Unrelated: I visited and toured Bill Holland's frame fabrication shop outside San Diego back in 2013.
    Do the math.

  4. #4
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    I retire cockpit parts when there's notable gouging from wrecks, that's for sure. Haven't had to do this with a stem, but I retired a handlebar last fall because of damage sustained in a crash. Not even a bad crash. Just hit things wrong. A rock gouged them in one spot, and in another, my dropper lever clamp scored the bar. I rode out, but was nervous and riding super chill the whole time.

    I'd also replace if there's any notable corrosion or oxidation occurring. Anything galvanic near the bolts, or anything like that. I haven't had that happen to any of my bikes, but I've seen it on others.

  5. #5
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    Good feedback. I suppose I should retire the stem. The gouges were years and at least 10,000 miles ago and I never noticed any weird feeling. I did a decent job filing the edges but its definitely missing a couple cubic millimeters of material. The bars twisted and it grinded on the back of the stem where it clamps to the steerer tube. It's pretty burly and overbuilt freeride stem so I figured it's not a big deal. I used my digital caliper and the faceplate/stem clamping surface width is 50mm. That's 4mm wider than the Paul Component Boxcar stem. I wish the width of stems was more commonly stated.

    My understanding is that my 7075 alu stem is less prone to fatigue due to corrosion whereas 2024 alu like a Paul Component doesn't hold up to corrosion as well. I also wonder how pure the 7075 is anyway, the Chromag stem doesn't have a country makers mark. Cutting some grams would be nice but not the priority.


    I mention Paul Co because they're in California, I'm in California, the stems are light enough and the owner got back to me regarding questions which is a good sign to me. Never bought Paul Co before.

    I wonder what the error rate in the Holland Cycles test was. And if the test was peer reviewed and repeated by any third party. Somewhat suspect when the company performing the test finds that their product lasts the most cycles. Not that its worthless, also not surprising the company producing the stem is the only one investing in testing it. I'd like to see this data become more available and see some meta analysis.

  6. #6
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    One thing I do if I'm nervous about a bar or stem is just put a heck of a lot of force on it in different directions. I figure if it doesn't fail then, it won't fail under riding loads. It's a judgement call as to how much force to apply vs what's going to occur while riding.

    As far as Bill Holland, in my meeting and tour of his shop I got the sense that he's totally legit. He seemed totally down-to-earth and there was nothing about the materials or his methods that he didn't or wouldn't discuss. However, that's just my impression.
    Do the math.

  7. #7
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    Quote Originally Posted by flypower View Post
    I wonder what the error rate in the Holland Cycles test was. And if the test was peer reviewed and repeated by any third party.
    Companies do all sorts of in-house testing that's not peer reviewed. All of 'em do (or at least, the ones I'd be willing to purchase from do). Most don't share the results, though, because it's considered a trade secret in many cases.

    I've seen the testing rooms at a number of component manufacturer facilities, and the way they test a given component is always a little bit different, too. A fair number build their own testing rigs, too. These places always keep guests a certain distance away from those testing rooms, and aside from occasional videos on youtube, I've never seen one in operation while I was there.

  8. #8
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    I've seen the testing that they* do for handlebars and the handlebars all broke before the stems did.

    * Zedler, Syntace, and other German testing sources

  9. #9
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    Quote Originally Posted by Harold View Post
    Companies do all sorts of in-house testing that's not peer reviewed. All of 'em do (or at least, the ones I'd be willing to purchase from do). Most don't share the results, though, because it's considered a trade secret in many cases.

    I've seen the testing rooms at a number of component manufacturer facilities, and the way they test a given component is always a little bit different, too. A fair number build their own testing rigs, too. These places always keep guests a certain distance away from those testing rooms, and aside from occasional videos on youtube, I've never seen one in operation while I was there.
    My concern with companies building their own testing methods to test their stem development against is that they build stems that are strong for their testing system. That system might suggest those stems are strong under those tests and that some other manufacturers stems are weak under those same tests. I wonder how many times they repeat the tests. This all sort of seems like helmet safety testing. Little peer review and little available information.

  10. #10
    since 4/10/2009
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    Quote Originally Posted by flypower View Post
    My concern with companies building their own testing methods to test their stem development against is that they build stems that are strong for their testing system. That system might suggest those stems are strong under those tests and that some other manufacturers stems are weak under those same tests. I wonder how many times they repeat the tests. This all sort of seems like helmet safety testing. Little peer review and little available information.
    To some extent. But how many different ways can you test a product like a stem? There might be subtle differences, but they're not likely to be huge. But, enough to make it more difficult to compare tests between two different companies.

    And further, the test posted above was for quill stems only. There were two bolt failures, but most of the others were pretty specific to quill stems.

    Cracked in quill at bottom weld.
    Cracked in extension at quill.
    Welds polished around quill. Did not break.
    Cracked in quill, across weld.
    Cracked in quill, across weld.
    Quill cracked below bottom weld.
    Cracked along top of extension and on the compression side of quill weld.
    Cracked in quill, across weld.
    Cracked in extension at handlebar clamp. Across weld.
    Threadless stems are a good bit more durable, and I'm sure you can make a solid argument that shorter ones are even more so. Failures seem to be rare enough that finding reports of anything more than faceplate cracks doesn't turn up a lot (and mostly people TRYING to break stuff).

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  12. #12
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    I buy name brand non-weight weenie stems for an extra safety factor - Syntace and Shimano Pro are favorites. My bars may be 130g carbon but that stem is 150g forged aluminum. Don't want to do a George Hincapie (yes I know that was steerer crash damage).

  13. #13
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    Quote Originally Posted by Harold View Post
    To some extent. But how many different ways can you test a product like a stem? There might be subtle differences, but they're not likely to be huge. But, enough to make it more difficult to compare tests between two different companies.

    And further, the test posted above was for quill stems only. There were two bolt failures, but most of the others were pretty specific to quill stems.



    Threadless stems are a good bit more durable, and I'm sure you can make a solid argument that shorter ones are even more so. Failures seem to be rare enough that finding reports of anything more than faceplate cracks doesn't turn up a lot (and mostly people TRYING to break stuff).
    Fair points and really I'm not too concerned about it. I just wish there were some industry standards that were available and it'd be nice to know which variables are being controlled. I can better information on ball bearings from Enduro and Ceramic Speed than I can get on stems and I'm really not worried about getting hurt cracking ball bearings. Of course, that's a function of the American Society for Testing and Materials (ASTM standards).

    I can think of a handful of variables and can imagine there are plenty of different ways to apply force to a stem. Hire a team of engineers and they'll come up with a bunch more ideas. I do wonder how many companies have tasked a design team specifically with the development of the testing system. I should probably start asking companies more about the testing process they use.

    One could use an angle guide jig to test different angles of applied force and do it at different angles with different amounts of force with different amounts of weight already fixed to the stem or handlebar, etc. I figure my stem is cycled through 100 different types of force every minute of rough riding. I've done thousands of miles with a Revelate Designs handlebar bag and feedbags. Sometimes the feedbags have 1.5 liters each and I've fit a 64 oz Nalgene onto a King Cage Manything Cage onto one of their stem cap bottle mounts. So, lots of weight applied at different angles with a lot of different amounts of force applied.

    I can also see problems with standardized testing for stems being a cost prohibitive part of production. But I am not a big fan of riding components that doesn't have a safety standard. Having dabbled a bit with rock climbing and knowing a bit about those standards, I feel that cycling is a little loose when it comes to accepting things as 'safe'.

  14. #14
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    Quote Originally Posted by flypower View Post
    I feel that cycling is a little loose when it comes to accepting things as 'safe'.
    Yes, it is. FWIW, the Euro standards often do have requirements for more standardized testing. Since you seem to be interested in that, take a look at some of those.

    It's infinitely better now than it was, say, during the weight weenie craze of the 90's when stuff was drilled out excessively, compromising the product.

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