Stem Snapped, help?

when installed correctly, it'll stand the test of time.

i.e. a poorly fitted Chris King headset won't despite being a 'fit and forget' headset.

I concur, it looks like it wasn't attached completely evenly, it's right up against it at the top so I imagine there will be a healthy gap at the bottom (can't tell from the photo however) when there should be a gap at the top and bottom (I imagine, as this is how my stem looks when attached)

The fact it cracked there isn't completely surprising as this is the section with the smallest cross section and therefore the weakest so with Rod yanking away at the bars this is the section that will suffer the most and eventually ping, especially when it hasn't got as much flexibility to spread the stress due to the clamp being right against the stem at the top. Does that make sense, bit tired at the mo!

Although the fact that you can get Thomson clamps also brings into question the quality of the clamp to start with!

^ yep this is why I'm assuming I over-tightened it (although I don't think the top gap was so small before it snapped).

As I say, the only surprising factor for me is that I have arms like Rasmussen and used a matchbox sized allen key to fit it - so, at the time, I think I'd been working on the assumption I needed to give it a lot of welly (and that only Geoff-Capes-types, with monkey wrenches and ultra-bling carbon needed to worry about torque).

Anyway, I refitted the replacement with a torque wrench (the gap is still tiny but at least there is one, and it's even with the bottom) so if it happens again I'll update the thread (or die horribly).

I was actually thinking the same thing after I posted my pseudo failure analysis, the gap probably closed when it snapped! Also you say you've done thousands of miles on it so fatigue has probably played a part in it as well.

At least you could replace the part without having to replace the whole thing!

However RPM was saying that those Thomson are prone to breaking when it come to track racing.

They break, especially on standing starts when you put in the beans. Dunno, how much do you weigh?

Aah, so a known problem! This does much to explain the fact they are sold separately.

Also a lots of stem nowadays have four bolts instead of two.