Life expectancy of a handlebar stem?

pjm-84
pjm-84 Posts: 819
edited February 2008 in Workshop
Yep I'm afraid mine cracked today whilst out riding the Primrose Path Audax sending me down the road in the process. Luckily it was single track descent with plenty of water and mud so I slid quite nicely on what it seems to be most parts of my body. Both knees right elbow, right side of the head and my upper back.

Thinking about sending TUNE a witty email and a nice picture showing the "two bits" of the broken clamping piece of the stem. However I'm wondering if their is a lifespan issue with these types of components. Something that I have to admit that I've never really considered before. I've had the stem just over 3years and it's worked it's way down to my training bike.

Thankfully I'm looking on the bright side and count myself very lucky at the moment. It could have been worse.
Paul

Comments

  • simbil1
    simbil1 Posts: 620
    Glad to hear you weren't hurt :shock:

    I've run stems offroad for 6+ years and have never seen or heard of one fail. Maybe it got over tightened one side or something causing some uneven stresses? If you can take a close up picture of the fracture it will be clearer what caused it.
    http://picasaweb.google.com/thefirstsimbil/Bikes
  • gkerr4
    gkerr4 Posts: 3,408
    i've never seen one fail - might well be worth sending something of to tune - at the least they might offer to replace the stem.
  • Raph
    Raph Posts: 249
    Very relieved to hear you didn't lose any teeth or worse.

    Sounds like a fault - not an issue of life expectancy. By fault I don't mean necessarily a manufacturing defect - is the diameter exactly the same as the bars? It's often said that .2mm difference will work ok, but it might put enough stress on the clamp that a tiny fracture will set it off to crack some time later when you hammer it down a hill. If not then it sounds like it could well be a manufacturing fault.

    I'm still using a couple of cinelli stems well over 20 years old, still occasionally hammering them over cobbles ... maybe I shouldn't be, but I think a good 10 years is a reasonable life expectancy for an aluminium part.

    I once had a stronglight crank start gradually disintegrating, bits of surface flaking away - if I'd carried on riding it I'm sure it would eventually have cracked and I'd never have had kids... but it was already over 10 years old at the time, and I think I'd started the rot by scraping it badly on rocks. Nowdays anodising and fancy lacquer seem to prevent the process beginning.
  • meagain
    meagain Posts: 2,331
    What everyone else says. I'm sure I've used ones 40-50 years old. Maybe the newer/expensive/ultra-light stuff DOES have a short(er) life, but THREE years is poor.
    d.j.
    "Cancel my subscription to the resurrection."
  • Raph
    Raph Posts: 249
    Maybe the newer/expensive/ultra-light stuff DOES have a short(er) life

    i'm sure it does - some of the most expensive stuff is often weaker than middle of the range gear. Showing my age here but I remember when Super Record was the same as Record gear but with cutouts - not all of it, but often it was better to go for the less swanky stuff cos it would last longer. I have a pair of old TNT hubs, they're nice and light but the bearings last about two trips to the shops.

    Don't know if any of this relates to stem mentioned above. Sorry, went off on one... :)
  • pjm-84
    pjm-84 Posts: 819
    Measuring the broken section the material is only 1.5mm thick which in comparsion to other stems in my garage is very thin.

    It's also very well machined but then again it's an Tune stem. In picture, taken from the top, the clamping gap looks tight however the gap at the bottom is the same. I was very impressed with the stem and I think in the search of performance its pared to the bone. Also being 6ft 5in and 15st 12lb I'm no lightweight racing cyclist although I can hustle up the hills pretty well.

    The stem has been on this bike since August 2006 and has done many thousands of Kms

    This is the newer version of my stem . Mine is the older model without the cut outs on the steerer section. Both have the same clamping plate.

    http://www.poshbikes.com/product.php?id=5

    Snapped image

    http://www.pjrm.co.uk/snap.htm

    The stem broke when I hit a relatively small but sharp pothole whilst braking hard on a single track 10-12% descent at about 23-25kph. I was running on 25c tyres pumped up to 100psi
    Paul
  • gundersen
    gundersen Posts: 586
    From 3TTT Users Manual:

    SPORT USE

    "We suggest you replace the stem after 10/15000 km sports use."

    "We suggest you replace the handlebar after 10/15000 km of competition use."

    OCCASIONAL AMATEUR USE

    "We suggest you replace the screws of the item every 2 years. We suggest you replace the stem after 5 years of occasional amateur use."

    "We suggest you replace the handlebar after 5 years of occasional amateur use."
  • simbil1
    simbil1 Posts: 620
    pjm,

    It's hard to see the fracture surface in the photo, but it looks like the fracture is shiny close to the bolt and rough every where else? That could indicate that a stress fracture had developed on the bolt side and was slowly growing. When you hit the pothole, there would not have been enough remaining material to take the shock and it all failed at once.
    Then again, it could be something else - returning it to the manufacturer is probably worth a go at least out of interest to see what they say.
    http://picasaweb.google.com/thefirstsimbil/Bikes
  • aracer
    aracer Posts: 1,649
    Whilst it's not nice to have bits fail (particularly parts like that), you are on the heavy side to be using such light parts. At your weight I'd seriously think about changing bits like that every couple of years if you want to use ultralight bits.
  • Blonde
    Blonde Posts: 3,188
    I know that forged rather than welded is best. Welds can break. Your stem doesn't look welded though. If you have previously crashed the bike it is possible that the metal was already fatigued or that only a tiny hairline crack had appeared which then resulted in a break at a later date. Some riders put their bike under more stress than others too. if you are a particularly aggressive or out-of-the-saddle-to-accelerate type of rider (who pulls on the bars a lot) you are more likely to get breakages. I don't think it's about weight as such, more about the stress you as a rider put the bike under. I know someone who has broken several stems and sets of bars. He is a tiny bloke, but is quite an aggressive rider and is out the saddle a lot. BTW 15 stone is not really very 'heavy'. My mum weighs about 20 stone and though not doing much cycling at the moment, did not brake any part of her bike when she was cycling.
  • redddraggon
    redddraggon Posts: 10,862
    It's a two bolt faceplate? I prefer to keep away from those, and stick to the "four bolters", they seem more reassuring (whether they are better is another matter - because I don't know).
    I like bikes...

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  • pjm-84
    pjm-84 Posts: 819
    Currently looking at the Thompson X4 and reviewing all my bike bits.

    The stem was a throw back from the Issac days (Isaac badged Tune stem) and will make a nice paper weight on the desk.

    I believe the stem broke on impact as the crack noise was very loud to the extent I thought the forks had broken. Both pieces are rough.
    Paul
  • aracer
    aracer Posts: 1,649
    Almost certainly a fatigue crack - they will let go with a bang when the crack gets big enough that the remaining metal can no longer take the load. Can't remember enough metallurgy to tell you what the crack should look like exactly, but you should expect to see 2 distinct failure areas - one where the crack grew, and one where it finally failed.
  • dennisn
    dennisn Posts: 10,601
    Is it a forged stem(with some cnc machining) or a strictly cnc'd one? Forged items are
    generally stronger(hubs, stems, and the like). And isn't Tune a maker of "lightweight"
    items? Sometimes "lightweight" stuff is just that, kind of "lightweight", if you get my meaning.

    Dennis Noward
  • simbil1
    simbil1 Posts: 620
    From what I remember of metallurgy, the fatigue fracture can be smoothed off a bit from the two sides rubbing together, or have corrosion 'tide marks' if a stress corrosion crack or can just look more mucky that the final failure as it is older.

    Wiki has a nice pic of one on a failed crank arm:

    http://en.wikipedia.org/wiki/Image:Pedalarm_Bruch.jpg
    http://picasaweb.google.com/thefirstsimbil/Bikes
  • pjm-84
    pjm-84 Posts: 819
    Nope both parts rough and very even in texture with no signs of smoothing. Jaggered lines are horizontal, parallel with the top of the bars rather then pendicular to. Looks like it just ripped apart.
    Paul
  • pjm-84
    pjm-84 Posts: 819
    Stem update...

    Tune have come back to me. The stem is lifetime so they would like the clamp back to examine / test. They are going to send me a replacement clamp.... yikes.

    I also now have a very nice small torque wrench. The remaining bikes have all been checked and all were below the torque figures specified although my brake levers were clamped a little tight to the bars on my new FS MTB. :roll:

    I just can't believe the required torque figures for the stem clamps bolts . Trek 13 to 17N/m and 16 N/m for the Deda.
    Paul

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