Saturday, May 25, 2013

KCNC Skewers

Sheldon Brown teaches about the difference between "closed cam" skewers and "open cam" skewers.  The simply perfect Shimano skewers are an example of closed cam skewers.  I'm sure there are many examples of open-cam skewers, but one is my KCNC skewers that I bought with my custom-made wheels from White Mountain Wheels.

In 2011, after we got the bikes ready, gave some unfortunate sound-bites to the documentary film crew, and had a great ride from Valdez over Thompson Pass and into the late-evening half-light, my KCNC skewer opened on my front fork, a bump caused the fork to separate from the wheel, and I dented the pavement with my (thankfully helmeted) melon.  That was the earlier version of the steel Gunnar fork without lawyer lips.

Since then I've been manic about checking and re-checking my skewers while riding.  I nonetheless convinced myself the first failure was operator error and I put the skewers to use with my Hed wheels on the rebuilt P2SL.  Today near the end of my ride I was descending a slight grade when the rear wheel separated from the bike, rolling out the back of the horizontal dropouts.  The bridge of the rear brake landed on the tire and I was able to stop without incident.  While replacing the rear wheel, I noted my front skewer had worked itself slightly loose as well.

Looking for others with similar problems, I found one advertising pitch:

"KCNC skewers are some of the most exotic and durable road skewers on the market. Get your KCNC products from Zen Cyclery."

Sheldon writes about open cam skewers that they were considered to be better because they could be made marginally lighter than closed-cam skewers.  But, he concludes, "The exposed-cam skewers are generally OK for vertical dropouts in back, and for forks with "lawyer lips", but should not be relied on with horizontal dropouts or plain forks."

I suppose I could put them back on the Gunnar, the one bike I have in regular use with vertical dropouts and lawyer lips (on the new fork).  I think I'll go a step further, however, and pitch them.  Saving a very few grams of non-rotating mass just is not worth it.


sam said...

Glad to hear that disaster was averted. I wasn't convinced that your skewer was the issue in Alaska, but with this additional data point, it certainly seems to at least be a contributing factor (though that rock would have caused a crash regardless).

I wasn't aware of the functional difference between cam types, thanks for the pointers. I have a pair of KCNC skewers that have been on order from Jenson for months now, but not delivered. I'll likely not use them at this point. Agreed that 50 grams is not worth the risk.

The shimano skewers seem to be the ideal design. Easy to use, and as far as I can tell, bulletproof.

Unknown said...

After your heads-up before Mountains, I checked them pre-ride, and then again mid-ride, and finally after. They held like champs. I wonder if yours are defective somehow. In any event, I have vertical, so maybe less of an issue. I have plenty of spare skewers if you'd like some.

Max said...

Yes, I'm confounded as to why mine are problematic while others do not seem to be. (There is very little KCNC bashing online.) Hard to imagine what about such a simple mechanism could be defective.

Damon, feel like reporting on what it's like riding 13 lbs of glue at high speed on the descents around Blacksburg?