I've been riding a recalled 140mm Control Tech stem since 1993-ish.  It's got probably 100,000+ km's on it and it's still going strong.  Yeah, I'm a dipstick for not swapping it out, but at this point, if it was piss-poor, I'd have two fake front teeth and a huge dental bill by now.  Errrr - wait a second, I do have two fake front teeth, but the ol' man got stuck with that bill back in 1993 and that is a story for another day!

So, what's my point?  My point is that a year or so ago, I got all freaked out by stems that were being sold that weighed less than 100 grams.  Saving a few measly grams on a stem didn't seem quite right, so instead of just bitchin' to my buddies about how people are crazy ;-), I designed and built a fixture to test these superlight stems until failure.  I found out some interesting things (sorry, can't tell you all the details since samples and fixtures cost money) along the way.  And, by the way, it was a long way - some of the better performing stems stayed on the fixture 24/7 for more than a week!  Others didn't make it more than a day....

This time around, I knew I wanted to give out the information for free, so I tried to streamline the process as best I could - yep, I'm that lazy and cheap!  I tested one stem (a 1" steer tube clamp Control Tech) in the vertical direction at the maximum level my test system was capable of, ~1000 lb.  I cycled in one direction until the stem failed.  I thought destruction would be had quickly...

5,026 cycles later, I had my desired result:

Figure 2.  Broken stem on the versa-fixture!

and made sure that I had the momentous occasion preserved in video format:

(click on image to view a ~165 kb *.wmv file - need windows media player to view)

For all you material science and failure analysis experts out there, here are some close-ups of the failure surface so that you can try to determine what happened:

Figure 3.  Failure surface shots.

Other than this kind of stuff being real exciting to watch and obsess over, what can we all learn?  We should be able to take away some insight into where a stem is most likely to fail, and subsequently, where we should be inspecting them on a regular basis.  When I inspect my stem I hit the following spots with the ol' eyeball:

-extension tube/steer tube clamp junction

-bar clamp/extension tube junction

-around the heads of any faceplate bolts

-center span of the faceplate

-around the heads of any steer tube clamp bolts

This is by no means a complete inspection list, but I reckon its as good a place as any to start.

Did I mention that I was impressed with this result?

Impressed?  Updated!

8/27/05

Words and Images by: Kraig Willett

Back in April, I received (for free) two high-zoot carbon stems and two carbon handlebars from Zipp for evaluation/publicity purposes.  As is the case with new product introductions, Zipp was hot to ge

cyclingnews.com

pezcyclingnews.com

roadcycling.com

I could continue with the links, but the sites linked to above all kind of say the same thing - and I don't want to bore you with any more techno-babble.