Looks to me like the clamp bolt in the stem on the right may not be original. Almost looks like a hex-head bolt for hex key/allen wrench.
But that's beside the point.

If you visit Hazardous bicycle handlebar stems you can see examples of failures of stems similar to the left hand one. Rather chilling. I haven't heard of Cinellis failing that way, but that may be just because they are relatively recent and made very well. Could be a different story when those become as old (and treasured) as some of the IAs (similar to the right hand model).

Ben

Did not see an example. The second and third picture are of the same stem, Modolo, that looks like the inverse design of an XA not the one on the left from the OP.

I don't know whether it's a coincidence or a real pattern, but: all the stems that I've seen, that failed in this way, were 3TTT stems.

https://lh3.googleusercontent.com/-V...2/IMG_8250.JPG

Correct, approx. 1 cm fore - aft. Cinetica also offered the same less integrated bar.

Interesting approach. I like the idea but the execution looks like it was a bit challenging, aesthetically.

That was my first observation. In theory this means less deformation on any given section of the clamp, which should mean less likelihood of failure.

I would guess that in practice it depends on the thickness and width of the clamping area, and the quality of the metal used. And the details of whatever forging technique was used. That's just a techie-sounding way to say either one could probably made to work just fine, or to fail if made wrong. So it probably boils down to aesthetics.

I have one of each (the OPs left example on the Nishiki and the OPs right example on the Raleigh). Both SR stems from the late 70s. They both work just fine for my purposes. As the guy who fell off the Empire State building said, while dropping past the 58th floor - "everything seems just fine so far".

I was going to say that!:) I decided to work with what was given. From a design POV, if they were designed by the same experienced person, it is likely that they would be equal in overall performance, but I am sure they were not. In todays design efforts, FEA along with other tools would be used to ensure there would be a margin of safety to avoid litigation or name brand erosion.