Back in the early 70's we sold mostly French bikes in the entry level to mid price range models. The better quality Italian bikes that we carried came with Cinelli or 3TTT forged stems plus we sold British and Italian frames.
French size 22mm Cinelli and 3TTT stems were rare as hen's teeth. Standard 22.2mm stems plus Cinelli and 3TTT bars too.
We were young and dumb back then. It was common to fit a wrong sized bar into a stem. Occasionally one of those stems made for a 26.4mm or 26mm bar broke when trying to clamp down on a 25mm or 25.4mm bars.
By the mid 70's common sense, conventional wisdom and experience (bad) and that practice became a no-no among knowledgeable bikies...
Here's a Cinelli 1a stem that that I'd been using since 1975 with 25mm bars. A few years ago I decided to install wider bars with a larger center section. There was a high pitched musical ping as the front of the stem flew off when I gently tried to expand it.
This is a 3TTT Record stem someone gave me on close inspection, I found a bunch of cracks.
The cracks could have resulted from clamping down on an undersize bar or a flaw in the metal called a seam lap or both?
Both of those stems were made of forged aluminum as are the other Cinelli and 3TTT stems mentioned above.
When you buy a used stem, you have no idea of it's history!
It's important to closely inspect a stem - any stem - before using it. Anything that looks odd should be checked with a 10x to 15x loupe or magnifying glass. Closeup pictures with a digital camera can work too.
A few years ago I bought a new Nitto Pearl stem. As I was looking it over, admiring the beautiful finish, I saw something that looked like a scratch. On closer examination I found that it was a crack, either a material or forging flaw.
In their defense Nitto has one of the best reputations for making quality products in the bike industry. Any manufactured products could have unknown defects!
After some searching I found their Japanese website and emailed them pictures with the details.
They got back to me the same day. I received a new replacement stem sent directly to me from Japan the next day.
Nitto even included a prepaid overnight shipping package for returning the defective stem to them so that they could quickly analyze it! They told me that they reinspected all of their inventory.
Have you ever tried to deal with an Italian manufacturer???
To change the subject a little, in the early 70's I had 2 bike boom cast aluminum (death) stems break off while I was test riding customer's bikes, also the top of a steerer on another bike.
I started doing a crude test before getting on any bike that I wasn't familiar with. Holding the bars I subtly lift the front wheel about 2" and bounce it a few times to see if anything feels loose. Over the years I've come across stems, steerers plus fork crowns that were ready to fail.
verktyg
Chas.