Cracked Thomson Stem faceplate 25.4

[John U]

Super suprised to notice this just now.

I've been using Thomson stems for 18 years. I fell in love with the Elite when I discovered the non-knee gouging design on the back of the stem. None of them have ever given me any issues. Always carefully torqued to the correct levels. Even more so with this particular one as they're holding Easton Carbon Monkey Lite bars (probably means nothing to quite a few of now ).

This is the first silver one I've ever had. Wonder if there's any difference in the make up. I've got a spare black 25.4 stem. Looks like I'll need to use it.

 

[Oddjob]

Has been known to happen in older ones. Haven't seen it in more modern ones.

Should always use grip paste, torque wrench and do the bolts up in a cross cross pattern.

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[Flow-Rider]

Pretty sad if you can crack one with carbon bars, maybe it binds on the boltholes when you pull it down too far.

 

[John U]

Quite literally done by the book. I've got the Thomson instruction booklets wedged in behind my shadow board. I follow virtually everything they suggest.

Greased the threads and not the heads. Torqued to 5.6 Nm (not the recommended 5.5Nm) with one of these. I guess that 0.1Nm shouldn't be a deal breaker and better to go a 0.1Nm too tight than 0.1Nm too loose. My torque wrench won't do 5.5Nm. Equal gaps on both sides of the face plate.

It must just be an age thing as it hasn't had a huge amount of work, but it's at least 8 years old. I swapped it out for an identical black one tonight.

Still great stems. I imagine if it had let go I still would've had enough control to stop.

 

[The Duckmeister]

Basic metal fatigue, which aluminium is particularly prone to.....

Stem faceplates don't contact the stem itself (otherwise it wouldn't clamp the bar properly), so the bolt tensions are trying to bend the plate around the bar. 25.4mm forms a tighter bend, therefore more stress through the plate vs bigger-diameter bar -> increased risk of fatigue crack with age.

 

[nzhumpy]

I had a simlar issue a few years ago, not the faceplate but still a failure...contacted the local distributor and had new one within the week