New bike - stem clamp not tightened resulting in catastrophic failure

[4F]

Wouldn't have happened with a quill stem, old skool rocks

 

[Norm]

I think that several have misunderstood the OP. Or maybe I have.

The way I have read it, it's not the clamp from the stem to the steerer which went but the clamp from the stem to the bars.

So, for instance, a quill stem could still fail if not properly tightened onto the bars, the stem wouldn't be damaged and so on.

I can also imagine (but only just) that if the bars were just clamped by the top two bolts, for instance, that it could feel ok to someone who hadn't ridden for a while until both of those bolts sheared and dumped you face first onto the tarmac the first time you braked hard.

Not supporting the OP or disputing many of the counter claims, just that I think many people are considering the clamp at the wrong end of the stem.

 

[4F]

but the clamp from the stem to the bars.

So, for instance, a quill stem could still fail if not properly tightened onto the bars, the stem wouldn't be damaged and so on.

yep same clamp as we are all referring to. Given that I have to thread my bars through my quill the only way my bars could drop off in the alleged same way would be for the quill to fracture.

Even more unlikely a scenario than the "client".

 

[youngoldbloke]

If you are worried about it happening to you fit these.

 

[Norm]

yep same clamp as we are all referring to. Given that I have to thread my bars through my quill the only way my bars could drop off in the alleged same way would be for the quill to fracture.

Yes, I can see that (although the fracturing quill was what I meant) but the other comments about, for instance, damaging the stem or the bike becoming uncontrollable before the failure.

 

[Mark_Robson]

Couple of rides in the stem clamp drops off, bars with it. Appears not to have been sufficiently tightened. No serious injury, but a long walk home.

Although the story has evolved from the OP the above suggests to me that the "clamp" failed because it was slack. If the face plate was that slack then the bars would move laterally as well as rotate. This IMO would make for an unridable bike.

 

[abo]

Although the story has evolved from the OP the above suggests to me that the "clamp" failed because it was slack. If the face plate was that slack then the bars would move laterally as well as rotate. This IMO would make for an unridable bike.

I'd agree with this, even me being a total n00b. Even a small slackening of the face plate would result in the bars becoming loose enough for me to think 'something wrong here' and at least get off and have a look.

 

[ianrauk]

I'd agree with this, even me being a total n00b. Even a small slackening of the face plate would result in the bars becoming loose enough for me to think 'something wrong here' and at least get off and have a look.

Exactly. Even the most non bike mechanically minded would have felt something amiss.
I can't imagine the OP was so green as to have not noticed that the handlebars would have felt lose. They would have turned in the stem for a starters.

 

[zigzag]

the op story is dodgy that's for sure, BUT i've seen a front plate breaking off after a crash. the stem (not sure if oem or aftermarket) was installed on a good quality road bike, the crash was tipping over on a side at low speed. it was a two bolt clamp and the steel bolts came out with aluminium spirals around their threads. luckily another stem could be sourced and the rider continued his journey.

 

[Angelfishsolo]

I'm quite happy to accept that a faceplate could come off after a crash. However this is not what is being suggested.

the op story is dodgy that's for sure, BUT i've seen a front plate breaking off after a crash. the stem (not sure if oem or aftermarket) was installed on a good quality road bike, the crash was tipping over on a side at low speed. it was a two bolt clamp and the steel bolts came out with aluminium spirals around their threads. luckily another stem could be sourced and the rider continued his journey.

 

[colinr]

My sister had her handlebars come off due to a bolt dropping out of an adjustable quill stem. Probably worked loose over time, there's no way she would have been touching the bike with any tools, didn't suspect anything was amiss until she found herself holding the handlebars separate from the bike.

Point being, not everyone knows how to maintain a bike nor do they necessarily notice when something isn't how it should be. Even if it's blindingly obvious to you lot what ride bikes all the time.

I'm assuming the bike in question had flat bars, drops with a loose faceplate would just run away as soon as you leaned on the hoods.

 

[abo]

My sister had her handlebars come off due to a bolt dropping out of an adjustable quill stem. Probably worked loose over time, there's no way she would have been touching the bike with any tools, didn't suspect anything was amiss until she found herself holding the handlebars separate from the bike.

Point being, not everyone knows how to maintain a bike nor do they necessarily notice when something isn't how it should be. Even if it's blindingly obvious to you lot what ride bikes all the time.

I'm assuming the bike in question had flat bars, drops with a loose faceplate would just run away as soon as you leaned on the hoods.

I reckon I'd notice even a flat bar start to turn in the stem

 

[Angelfishsolo]

Subtle things like the gear shifters and brake levers being in the wrong place for example

I reckon I'd notice even a flat bar start to turn in the stem

 

[colinr]

I'm trying to visualise it. As long as you were holding onto the bars and not pulling hard on them (let's assume a very gentle ride) you could conceivable ride unaware of them being slightly loose. But loose enough to drop off, I have to agree that you'd be riding with your brakes perpendicular to the ground. I'd hope that would sound alarm bells, but you never know!

 

[Chris.IOW]

I'd hope that would sound alarm bells

Possibly not, the bell would be in the wrong place as well and therefore difficult to sound.