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Riding home after a late shift at silly o'clock in the morning there was a loud bang; it was all I could do not to go over the front of the bike. It was dark and I had no idea what had happened. More to the point I was doing 30mph downhill. The bike swerved right, I hit the tarmac scraped down the road on my back, off the side of the road down an embankment and into a tree..... a downhill skier could not have done it any better 10 out of 10 for style  41
Once I had checked all my body parts were in the correct place, I looked at my bike....
It appears that one of the two bolts holding the bars to the stem had snapped. The second bolt ripped out causing the handlebars to become detached.....
Luckily I had some electrical tape in my bag, I re-attached the bars and rode home  16
Looking at the stem.... two bolts???? What was I thinking????? What a s**t design....  14
Maybe I am being a bit harsh; I have had this stem for some time and I have used it on unforgiving territory, or British roads as they are also known.
Anyway; I have skin missing on my face, shoulder, hip and knee along with very colourful bruises on both of my thighs. Not forgetting the general aches and pains..... I am feeling very sorry for myself  2
I am writing this just to warn others to look very critically at their stem and ask yourself is it fit for purpose?
This incident could have been so much worse....

41 comments

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Al'76 [110 posts] 2 years ago
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Not criticizing, but did you mount the bar using a torque wrench? Could see this happening if the bolt was done up silly tight, but like to think it would not happen under normal circumstances....

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Gasman Jim [163 posts] 2 years ago
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I used to be a fan of the 2 bolt Thomson X2 stem.... until the faceplate deformed and wouldn't then grip the bars sufficiently to stop them rotating forwards when correctly torqued, (and I'm only 71kgs).

I now use the 4 bolt X4 stem on all my bikes. Much more secure.

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glynr36 [637 posts] 2 years ago
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Perhaps you should title this 'Do you trust your bolts'

The stem didn't fail the bolt did, most likely due to over torquing it.
The second came out due to the abnormal load on it more than likely.

Invest in a torque wrench.

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southseabythesea [150 posts] 2 years ago
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Ouch! I could add to that do you trust your LBS, when I got my cross bike home I gave it the once over and found that the headset bolts were loose even though they insisted giving it the once over before I took it home. Always check 'em with a torque key, bike shop or not.

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drfabulous0 [409 posts] 2 years ago
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Two bolts is a poor design as you now realise, if they are not tightened evenly then one can be taking excessive force, four bolts or one are better. I've seen a few failures like this though, threads stripped and cracks and even once a stem shear off at the weld, luckily none of these resulted in injury but poor manufacturing quality was the issue in all these cases rather than incorrect installation.

I've been a bike mechanic for many years and I have to warn you guys not to put to much faith in reccommended torque settings, it is not uncommon to do up stem bolts to the manufacturer's specification and find that the bars will slip under a slight load. An experienced mechanic can not only make a fair estimate of torque without the torque wrench but can also feel when the bolts are under sufficient but not excess tension.

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arfa [767 posts] 2 years ago
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Would you be able to name the brand ?

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stuke [335 posts] 2 years ago
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I had a stem faceplate fail once due to corrosion, it'd done a couple of harsh winters.
A big tug on the bars pulling onto a roundabout at rush hour and the faceplate disintegrated leaving the bolts in situ. Luckily I rode no handed across the roundabout like a boss carrying the bars, more luck than judgment mind  3

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SideBurn [890 posts] 2 years ago
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I have to admit I did not use a torque wrench, but I am not a ham fisted bugger. Obviously they could have been over or under tightened. But as I have said they have been fitted for some time. I am wondering if the bolts could have become brittle through use? Work hardened? So maybe I should have changed the bolts?The stem is an ITM Millennium, but now it has broken I think it looks a bit flimsy...
Thanks for the responses  4

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giobox [356 posts] 2 years ago
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SideBurn wrote:

I have to admit I did not use a torque wrench, but I am not a ham fisted bugger.

When I used a torque wrench for the first time I was very surprised at how little pressure the 4 to 6nm most stems (in fact most bicycle bolts) spec is. If you've never used one, there is a good chance you will be surprised at how much you are over-tightening everything on your bike. It's worth having a quick shot of one to get the feel.

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Jimmy Ray Will [487 posts] 2 years ago
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ITM Millennium!!! Isn't that over 10 years old? I think that, right there is your problem.

Truth is the stem/bar interface is never going to be that brilliant from an engineering point of view... but things have moved on significantly from those Millennium days.

Muchos kudos for simply taping your bars back on and riding home... that is truly hardcore!

Get well soon.

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SideBurn [890 posts] 2 years ago
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Jimmy Ray Will wrote:

ITM Millennium!!! Isn't that over 10 years old? I think that, right there is your problem.

This is what I am thinking.... I cannot be the only one with an 'antique' stem  39

Muchos kudos for simply taping your bars back on and riding home... that is truly hardcore!

Thank you  16

Get well soon.

Mind you, it was a choice between ringing 'er indoors at silly o'clock for a lift home..... or risk death with taped up bars....
Not much of a choice really  17

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farrell [1950 posts] 2 years ago
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Quote:

I am writing this just to warn others to look very critically at their stem and ask yourself is it fit for purpose?

Maybe *that* is what Chris Froome is doing?

http://chrisfroomelookingatstems.tumblr.com/

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jollygoodvelo [1477 posts] 2 years ago
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Jimmy Ray Will wrote:

Truth is the stem/bar interface is never going to be that brilliant from an engineering point of view... but things have moved on significantly from those Millennium days.

I've noticed quite a few of the pros riding one-piece stem/bar combinations recently. Seems like a far more sensible approach to me.

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gmac101 [135 posts] 2 years ago
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When you design a bolted connection like stem / bar joint you calculate the tension in the bolt that gives you a strong enough joint. The problem is that measuring the tension in the bolt is pretty tricky without special equipment so the most practical thing to do is measure the torque you impose on the nut or the bolt head as a "proxy" for the actual bolt tension. The problem is that it's not very accurate! It's a classic first year engineering degree lab to torque up a series of bolts in different conditions and then measure the actual tension in the bolt. If I remember correctly it's about +/- 25% accurate. The problem is that friction in the bolt/nut system eats up the torque and very little is used to actually tension the bolt but the friction in the system is also very dependent on condition. Some factors include, bolt & nut material, type of grease used (if any) location of the grease on the bolt, foreign bodies & corrosion. If you don't replicate the conditions the manufacturer assumed when they worked out the recommended torque you could be a long way out from the bolt tension intended. And of course we are all using calibrated torque wrenches aren't we? So Dr Fabulous0 when you torqued up to the manufacturers recommendation you may well have prepared the bolt better the manufacturer expected and so didn't reach the required tension.

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Kapelmuur [335 posts] 2 years ago
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Jimmy Ray Will wrote:

ITM Millennium!!! Isn't that over 10 years old? I think that, right there is your problem.

Truth is the stem/bar interface is never going to be that brilliant from an engineering point of view... but things have moved on significantly from those Millennium days.

Muchos kudos for simply taping your bars back on and riding home... that is truly hardcore!

Get well soon.

Oh dear, you've got me worried about my 40+ year old bike on which I'm planning to ride the Retro Ronde.

Will it fall apart on the cobbles? Is there any way to check, short of ultrasonic inspection?.

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MKultra [396 posts] 2 years ago
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I have never had a stem fail on me or a bolt snap (for now touch wood), I also have never used a torque wrench on ally or steel stems.

With the exception of carbon where it is critical to get it right with a torque wrench I would be of the opinion that if you don't have the feel for getting it right yourself with just an alan key then perhaps you should be taking it to the LBS rather than doing it yourself.

I await the storm of pedantic rage but be honest chaps, buying a torque wrench is not a cure for being cack handed.

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SideBurn [890 posts] 2 years ago
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Crosshouses wrote:
Jimmy Ray Will wrote:

ITM Millennium!!! Isn't that over 10 years old? I think that, right there is your problem.

Truth is the stem/bar interface is never going to be that brilliant from an engineering point of view... but things have moved on significantly from those Millennium days.

Muchos kudos for simply taping your bars back on and riding home... that is truly hardcore!

Get well soon.

Oh dear, you've got me worried about my 40+ year old bike on which I'm planning to ride the Retro Ronde.

Will it fall apart on the cobbles? Is there any way to check, short of ultrasonic inspection?.

Looking at my 30+ year old bike/stems they are very solid looking and look better engineered than this relatively modern stem. I have never known one ancient or modern breaking. I am reassured that no one seems to be saying, "This has happened to me...."
Suggests I am just unlucky...

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glynr36 [637 posts] 2 years ago
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MKultra wrote:

I await the storm of pedantic rage but be honest chaps, buying a torque wrench is not a cure for being cack handed.

That's exactly what it is a cure for, do bolt up to specified torque, then stop.
Not, tighten, tighten, tighten, and then a bit more till you think you got 11.8Nm

The thing is most people don't realise just how little 15Nm and less is, especially when they're swinging off the end of an XL length Allen key.

You can even get the ones that stop going beyond the set torque if you're really stupid/hamfisted.

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racyrich [260 posts] 2 years ago
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Not quite happened to me, but my clubmate's stem faceplate cracked. Luckily I happened to notice it when we were stopped, so a careful ride thereafter, no swinging out of the saddle. Stem binned.

I've had a nosebolt go on a Cinelli 1A stem, but that was due to overtightening. Very hard to get them tight enough to stop the bars moving if you hit a hole. After such an incident I wanged it up. Next day, speeding throguh some village in the Ras - BANG - bars shoot round and flop sideways. Lucky to stay upright there.

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jellysticks [95 posts] 2 years ago
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gmac101 wrote:

When you design a bolted connection like stem / bar joint you calculate the tension in the bolt that gives you a strong enough joint. The problem is that measuring the tension in the bolt is pretty tricky without special equipment so the most practical thing to do is measure the torque you impose on the nut or the bolt head as a "proxy" for the actual bolt tension. The problem is that it's not very accurate! It's a classic first year engineering degree lab to torque up a series of bolts in different conditions and then measure the actual tension in the bolt. If I remember correctly it's about +/- 25% accurate. The problem is that friction in the bolt/nut system eats up the torque and very little is used to actually tension the bolt but the friction in the system is also very dependent on condition. Some factors include, bolt & nut material, type of grease used (if any) location of the grease on the bolt, foreign bodies & corrosion. If you don't replicate the conditions the manufacturer assumed when they worked out the recommended torque you could be a long way out from the bolt tension intended. And of course we are all using calibrated torque wrenches aren't we? So Dr Fabulous0 when you torqued up to the manufacturers recommendation you may well have prepared the bolt better the manufacturer expected and so didn't reach the required tension.

I love this kind of stuff. Genuinely. I wish I knew about engineering.

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Flying Scot [918 posts] 2 years ago
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I remember these ITM 2 bolt stems failing about 10 years ago, the bolts were gash and there was the torque vs thread friction issues.

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SideBurn [890 posts] 2 years ago
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Flying Scot wrote:

I remember these ITM 2 bolt stems failing about 10 years ago, the bolts were gash and there was the torque vs thread friction issues.

I have been lucky for 10 years?  22

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gmac101 [135 posts] 2 years ago
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Careful Jellysticks who you say things like that to - most engineers can talk for hours about this rubbish if you let them - Let me tell you about inviscid hydrodynamics......

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Flying Scot [918 posts] 2 years ago
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SideBurn wrote:
Flying Scot wrote:

I remember these ITM 2 bolt stems failing about 10 years ago, the bolts were gash and there was the torque vs thread friction issues.

I have been lucky for 10 years?  22

Possibly, I just remember reading about it before, though they werent the only ones, I've no experience of it myself.

I'm using a 20 year old titanium quill stem on my road bike.

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dafyddp [391 posts] 2 years ago
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Glad you survived in one piece, a 30mph tumble in the dark must be horrific.
Outside of cycling, I enjoy a spot of rock climbing and it's interesting to compare the industry response when equipment fails like this. In the event of safety equipment failure, the standard practice is to send it straight back to the manufacturers, who by and large are incredibly responsive - precautionary recalls are not at all uncommon. SRAM hydraulic brakes aside, cycling manufacturers seem less bothered?

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surly_by_name [392 posts] 2 years ago
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drfabulous0 wrote:

Two bolts is a poor design as you now realise, if they are not tightened evenly then one can be taking excessive force, four bolts or one are better.

I've been a bike mechanic for many years and I have to warn you guys not to put to much faith in reccommended torque settings, it is not uncommon to do up stem bolts to the manufacturer's specification and find that the bars will slip under a slight load. An experienced mechanic can not only make a fair estimate of torque without the torque wrench but can also feel when the bolts are under sufficient but not excess tension.

Two bolts no worse than 4: http://www.eastoncycling.com/bike/wp-content/uploads/2010/04/RD-06-2Bolt... (Although now Easton have followed the fashion to 4 bolts, suspect you can't find this paper so easily on their website anymore.)

The bigger problem is not a faceplate that is too loose at recommended torque settings but one that is overtightened by someone who doesn't have the benefit of a torque wrench.

And the bit about "experienced" mechanics being magical - leaving aside the fact that this is a fairy tale, a mechanic who doesn't own/use a torque wrench doesn't deserve the sobriquet "experienced".

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MKultra [396 posts] 2 years ago
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surly_by_name wrote:
drfabulous0 wrote:

Two bolts is a poor design as you now realise, if they are not tightened evenly then one can be taking excessive force, four bolts or one are better.

I've been a bike mechanic for many years and I have to warn you guys not to put to much faith in reccommended torque settings, it is not uncommon to do up stem bolts to the manufacturer's specification and find that the bars will slip under a slight load. An experienced mechanic can not only make a fair estimate of torque without the torque wrench but can also feel when the bolts are under sufficient but not excess tension.

Two bolts no worse than 4: http://www.eastoncycling.com/bike/wp-content/uploads/2010/04/RD-06-2Bolt... (Although now Easton have followed the fashion to 4 bolts, suspect you can't find this paper so easily on their website anymore.)

The bigger problem is not a faceplate that is too loose at recommended torque settings but one that is overtightened by someone who doesn't have the benefit of a torque wrench.

And the bit about "experienced" mechanics being magical - leaving aside the fact that this is a fairy tale, a mechanic who doesn't own/use a torque wrench doesn't deserve the sobriquet "experienced".

So they were all rubbish before carbon came along and torque wrenches were needed?

Piffle.

It's the over complication of the subject/trade by middle class people with more money than sense, much like when they all thought they could retrain as plumbers back in the early noughties.

No it's not magical but neither is throwing money about or snobbery.

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surly_by_name [392 posts] 2 years ago
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MKultra wrote:

So they were all rubbish before carbon came along and torque wrenches were needed?

Piffle.

It's the over complication of the subject/trade by middle class people with more money than sense, much like when they all thought they could retrain as plumbers back in the early noughties.

No it's not magical but neither is throwing money about or snobbery.

My father - who I don't think was unusual among his generation - was able to work on the engine of his car. I seem to have a vague recollection of him having the top of the cyclinders off on at least one occasion. You would open the bonnet and there were all of the mysteries of the internal combustion engine laid out in front of you (with lots of extra room to stick your head in and swear when things didn't work as they were supposed to). The ECU in a modern vehicle (or a hybrid engine) isn't the kind of thing you fix on your driveway on a Saturday morning.

I don't think mechanics were rubbish before carbon came along. I think they were skilled in working with the technology they had in front of them. Technology has, I imagine you will concede, moved on a bit.

A BBB torque wrench costs c.£45. If this is too bourgeoisie for you, you can purchase a Ritchey torque key (with a 5/4/3 and T15 bit) which will let you know when you've reached 5nM (recommended for most stem bolts at steerer and handlebar; in fact probably about the correct torque for pretty much every bolt on a road bike you want to tighten regularly (bottle cage bolts, seat pin collar (although my Thomson collar has a ludicrously low torque setting of 2.8nM - try and get that right by hand) - not cranks or pedals) for a much more proletarian £12.

Nothing is without risk. Using a torque wrench and following manufacturers recommended torque settings is a (not particularly expensive, empirical) means of managing some of the risks inherent in working on your own bike. (Or you can manage the risk by taking your bike to a shop.) If you don't follow manufacturers instructions and something goes wrong then its easy to lose the argument that it was partly your fault.

If you spend a lot of money on bikes and parts (particularly lightweight parts, whether in carbon or aluminium) and you don't use a torque wrench (or you rely on a mechanic who doesn't use a torque wrench) you are an idiot.

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MKultra [396 posts] 2 years ago
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surly_by_name wrote:
MKultra wrote:

So they were all rubbish before carbon came along and torque wrenches were needed?

Piffle.

It's the over complication of the subject/trade by middle class people with more money than sense, much like when they all thought they could retrain as plumbers back in the early noughties.

No it's not magical but neither is throwing money about or snobbery.

My father - who I don't think was unusual among his generation - was able to work on the engine of his car. I seem to have a vague recollection of him having the top of the cyclinders off on at least one occasion. You would open the bonnet and there were all of the mysteries of the internal combustion engine laid out in front of you (with lots of extra room to stick your head in and swear when things didn't work as they were supposed to). The ECU in a modern vehicle (or a hybrid engine) isn't the kind of thing you fix on your driveway on a Saturday morning.

I don't think mechanics were rubbish before carbon came along. I think they were skilled in working with the technology they had in front of them. Technology has, I imagine you will concede, moved on a bit.

A BBB torque wrench costs c.£45. If this is too bourgeoisie for you, you can purchase a Ritchey torque key (with a 5/4/3 and T15 bit) which will let you know when you've reached 5nM (recommended for most stem bolts at steerer and handlebar; in fact probably about the correct torque for pretty much every bolt on a road bike you want to tighten regularly (bottle cage bolts, seat pin collar (although my Thomson collar has a ludicrously low torque setting of 2.8nM - try and get that right by hand) - not cranks or pedals) for a much more proletarian £12.

Nothing is without risk. Using a torque wrench and following manufacturers recommended torque settings is a (not particularly expensive, empirical) means of managing some of the risks inherent in working on your own bike. (Or you can manage the risk by taking your bike to a shop.) If you don't follow manufacturers instructions and something goes wrong then its easy to lose the argument that it was partly your fault.

If you spend a lot of money on bikes and parts (particularly lightweight parts, whether in carbon or aluminium) and you don't use a torque wrench (or you rely on a mechanic who doesn't use a torque wrench) you are an idiot.

The fact that you have manged to write 5 paragraphs defending the gross over complication of a simple mechanical task that the non-cack handed among us can do with their eyes shut just proves me right.

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glynr36 [637 posts] 2 years ago
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MKultra wrote:

The fact that you have manged to write 5 paragraphs defending the gross over complication of a simple mechanical task that the non-cack handed among us can do with their eyes shut just proves me right.

Over complication? Its the way it should be done properly.
And you say non-cack handed, how do you know your bolts are in the right torque range, suggests a lack of engineering knowledge...

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