Broken stearing tube

My guess to was that perhaps I over tightened the new stem which compromised the integrity over a short time. I will have to check when I get the bike back if the shorter stem was longer but when I changed it out there was equal space when screwing in the top cap.

Unfortunately I didn't any others pics with a closer detail of the crack before I dropped off the bike.

I'm curious to see what Fox will say. Shop says they will look to see if the fork can even be re-built with an average cost around $175. The other option would be that they may offer between 10-40% off a new fork.

What would the right amount of torque be on tightening the stem to the fork?
 
Found a closer shot of it
8B474A39-525F-4A94-88BA-857874B6B2E3.jpeg
 
Hmm, that's wild. Not sure I'm buying the over tighten thing or that the new stem was too tall. Since it snapped off below it all. Possibly over tighten but unless you put a ratchet on it I'm not sure you could really do that kind of damage with an Allen key.
 
I'm with @gtluke on over tightening because those stem bolts are not terribly strong. I've stripped one relatively easily before. Thinking they will strip before doing any damage to the steerer.
 
I don't think tightening the stem actually damaged the steerer, It was that the stem didn't rotate under the torque of the crash.
with the age, and perhaps a little weakening at the edge along the star nut, snap!
 
classic case of catastrophic aluminum stress failure
no wonder Luke won't ride aluminum bikes, next year switching all bikes to steel and plastic
 
Is that dirt packed in the steerer tube attached to the stem? At first I thought it was the star nut but doesn't look like one I've ever seen before.

Speaking of star nuts, was it set to the correct depth? I would imagine a shallow setting on a star nut could play a factor.
 
From what I see of the picture, it looks like the steerer tube only went half way into the stem. My guess would be that there was enough leverage to rip it out if you bashed a rock.
 
Xler8 said:
Is that dirt packed in the steerer tube attached to the stem? At first I thought it was the star nut but doesn't look like one I've ever seen before.

Speaking of star nuts, was it set to the correct depth? I would imagine a shallow setting on a star nut could play a factor.
Click to expand...

star nut doesn't matter. once you tighten down the stem you can take the top cap off, doesn't do anything besides set the tension, which is permanent after the stem is clamped down.
 
fidodie said:
I don't think tightening the stem actually damaged the steerer, It was that the stem didn't rotate under the torque of the crash.
with the age, and perhaps a little weakening at the edge along the star nut, snap!
Click to expand...
doh, didn't think of that. but I guess. Seems like twisting the steerer apart would require a LOT of power.
 
qclabrat said:
classic case of catastrophic aluminum stress failure
no wonder Luke won't ride aluminum bikes, next year switching all bikes to steel and plastic
Click to expand...
yeah, F aluminum. I won't use it for frames or handlebars. It's method of failure is frightening. And it rides like shit.
It's getting better though. My thomson seat posts are amazing and they are aluminum.
There are now more than a few cars being constructed out of aluminum. It's traditionally never been used because of how poorly it rides and how poorly it reacts in impact. It shatters instead of crumpling, and it resonates like crazy. But with better blends and computer modeling it seems to be a thing that may happen. Aside from hoods and doors and other non structural body pieces like a pickup bed, the audi A8 is the only thing that comes to mind that isn't a boutique or sports car.
 
gtluke said:
yeah, F aluminum. I won't use it for frames or handlebars. It's method of failure is frightening. And it rides like shit.
It's getting better though. My thomson seat posts are amazing and they are aluminum.
There are now more than a few cars being constructed out of aluminum. It's traditionally never been used because of how poorly it rides and how poorly it reacts in impact. It shatters instead of crumpling, and it resonates like crazy. But with better blends and computer modeling it seems to be a thing that may happen. Aside from hoods and doors and other non structural body pieces like a pickup bed, the audi A8 is the only thing that comes to mind that isn't a boutique or sports car.
Click to expand...

The biggest reason why aluminum hasn't been used for chassis is it's so hard to work with. Welding is harder to do compared to the factory spot-welds done in the past. And it's nearly impossible to do a cheap/fast steel to aluminum fastening method. Like if you want to use aluminum frame rails but steel floors and bulkheads. Or ABC pillars made of steel but aluminum bulkheads, etc. Not to even mention galvanic corrosion. Plus aluminum has historically been expensive.

Much easier to make bolt-on parts that are heavy in steel out of aluminum to minimize weight. Crossmembers, suspension arms, door impact supports, etc. Body panels are actually hard as Aluminum is hard to stamp. Castings are much easier.

For this steerer tube, I'd want to see more close up pictures. It could have been a scratch on the tube 10 years ago from a loose & then spun stem creating a stress riser that took a long time to materialize.

-Steve
 
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