I think this has more to do with the practical dominance of vertical dropouts. You may have noticed all the recommendations against using external cams with stationary trainers though.

The cans of external type quick releases aren't made as eccentric as internal cams because it would make them uncomfortable to use. This not only limits the maximum possible clamping force (not really important since you don't really need or want the absolute maximum for every day riding), but it also makes it easier to misjudge and undertorque them. And then there are all the cheap versions with horrible plastic cam beds that can also come out of alignment and cause catastrophic failure. Internal cam is simply a better design.

Faiwheel Bikes skewer review provides some insight in the functional differences between various quick release designs (see the listed cam travels for example): High End Skewer Review - Fairwheel Bikes Blog

So it is not that external cam skewers cannot or don't provide suffice clamping force, but rather that it can be harder to achieve and maintain sufficient clamping force due to the design and typical construction elements.

That makes sense, and is what I suspected.

I don't get what you're saying about the predominance of vertical dropouts and stationary trainers has to do with it, though. It is more important to have proper clamping force in adjustable dropouts, but as I've been saying, I doubt it is beyond the capability of the external cam design to deliver that force. Harder given the construction elements often employed in the design (like plastic beds, soft alloys, and short lever arms), yes, but in the same way a cheaply made internal cam skewers (and yes, before the CNC boom when making cool external cams possible, badly made internal cams existed and broke) didn't mean a fundamental failure of that design, so too do not the cheapest, worst made, no-brand and Chinese knock-offs mean the external cams don't work either.

As for the stationary trainer use, isn't it simply that the clamps need a solid purchase on the skewer, which the housing of an internal cam provide?

product in question

http://www.amazon.com/XLC-Wheel-Skew...release+skewer

ok, i should be just letting this go, but what the hell, here we go.. its just possible that in using alloy they did not use a strong enough metal for securing the wheel to the frame dropout.. not vertical drops.. just cannondale standard alum frame, in fact i examined the QR part in question, and the surface on the clamping suface , that sould have teeth to cut into the dropout surface was smooth, i took this QR to the bike shop, and the owner gave me a lecture to "NEVER USE THESE HEX KEY QR's ever again" because the metal used is not strong enough to hold to the surface of the dropout, and the clamping method is so easy to over or under tighten, and even when you have it at the right amount its still not worth the gamble,, unless 26gm is per wheel is worth that risk.. gave me a set of new QRs if i would let him destory the ones i brought in... i will say this.. using standard QR alum, or steel, this has never happend to me again.. but i will take fulll responsibility but i have never had a total fail of any QR besides thoes,, they may be s simple device,, but its not worth the risk for a clean look or the weight savings... but im not an authority on any of this stuff this is just personal experience,, i aske the shop owner if the accident was my fault.. he said NO.. its a bad design.. and DONE!!

Vertical dropouts more accurately position the wheel and require less clamping force as the dropout itself restrains the wheel from being pulled forward by the chain.

Nearly certain this has everything to do with the trainer design and nothing to do with the clamping force of an external cam skewer.

Not all external type quick releases have a limited stroke. And, all else equal, a limited stroke also has the exact opposite effect of what you seem to be implying. The clamping force generated by a skewer comes down to input force times mechanical advantage of the skewer minus friction. Mechanical advantage increases assuming a constant lever arm length and decreased eccentricity of the cam. Internal cam skewers have an advantage in that they have very low friction by means of using hardened steel parts with lubrication. External cam skewers rely on anodized aluminum against reinforced nylon (or similar polymer) which, combined with some road debris and maybe some corrosion on the pivot, has far higher friction. A little chain lube on that parts solves that if/when it becomes an issue.

Fact is, external cam skewers can be made lighter weight than internal cam and still generate sufficient clamping force. That cheap versions exist doesn't make all of them junk, just the cheap crap ones.

While you seem to understand the relevant issues, you keep taking it back to the shop owner, whom you claim asserted the design of hex key skewers is bad prima facie, however I think this is the completely incorrect takeaway.

Besides being functional, bog-simple, light and aerodynamic, they also offer security against theft and accidental release. Whether or not any of those features are worth two cents to you is beside the point; they're elements of the design. Not bad design at all.

What seems to have happened here is that you bought the cheapest hex type you could find, and received a product generally inferior (probably; grip teeth being an absent feature, alloy another possible point), but definitely inferior to your needs. You may have over-torqued them, as well, beyond their rating, and perhaps beyond what was necessary for retention, but we can't know either thing.

So the take-away should be simply that those were bad hex skewers. The purchased ones you linked to were an off-brand at $13/pair. Control Tech, though not under the same ownership they were in the early '90s, has been making these hex skewers for probably two decades at least; they are $60: http://www.amazon.com/Control-Tech-S...ol+tech+skewer

I cannot certify that the Control Tech skewers would sustain the torque you applied the others, but given the longevity of the design, the presence of grip teeth on the nut, and the greater cost, I'd say the odds of them being better than those which you purchased are very high. I used Control Tech hex skewers, two pairs, back in the early-to-mid '90s, on two Bridgestone MTBs with adjustable dropouts without any problems during road or trail use.

As for the risk of overtorque-ing hex vs. lever-throw skewers, I will agree it's greater for hex simply given the length of hex keys generally available and the general absence of user awareness with regard to metering torque when applied by hand and without a gauge. However, it's entirely possible to over tighten and ruin lever throw skewers as well, simply by overtightening the nut when the lever is fully open, and then forcing it closed. So it is absolutely not the case that lever skewers absolutely prevent orvertightening, though they do reduce the chance.

I wonder if the preset torque Allen keys would provide appropriate torque for secure engagement of the hex key type skewers. They generally come in 4 and 5 Nm settings IIRC. Just referring to the readily available ones that are offered for bike work by folks like Giant and Ritchey. I think they are all made by the same manufacturer and just rebranded. Anyway they are certainly compact enough to carry in one's one-bike or in-jersey tool kit. My Giant one comes with 4, 5, and 6 mm hex key heads. What size Allen key is required for the skewers?

"If you have any doubts about your ability to correctly install the race skewers, please return to your dealer to insure proper installation."

--- http://www.controltechbikes.com/imag...ace_skewer.pdf

Translation: it's not that hard.

I recently bought a frame with horizontal drop-outs, and asked the framebuilder if there were any caveats I should know about. The first thing he told me was not to use external cam skewers in the rear dropout, as he said the wheel will slip out of alignment. This is for a cross bike that is designed to ridden rough terrain.

Perhaps an external cam skewer would be "enough", but my experience with them is that they feel wimpy compared to the standard old style, so my anecdotal feeling matches what Sheldon Brown says. All but one of my wheelsets have the old-style cam, as they all have Shimano hubs. If you have vertical dropouts it's not an issue.

Years ago (when Sheldon was still alive and would post on the Forum) his site complained that the exposed can types could be tightened with the handle cam not properly seated in the curved spacer, resulting in a dangerous situation.

Interesting that this is no longer mentioned on the site...

While we're in the neighborhood,

could we dial in the meaning of "700c"?

This refers to a specific size (bead seat diameter) of clincher rim, & corresponding tire.

That tire has a width, measured in mm e.g. 25mm.

A QR skewer can be used in several wheel sizes.

Tubular rims are not 700c.

Only consider a weight weenie skewer with a vertical dropout frame.

Otherwise Just buy a Shimano Internal cam, steel sxkewer if you Don't have a vertical dropout frame .

People trash rear wheels first (rim damage) so rear skewers, from those discarded wheels , are abundant in Bike Shops.