An unexpected end to my ride today

[GoLefty!!]

CAp, I am experienced in fatigue of thin walled cylinders both due to pressure foreces as well as mechanical forces hence I am pretty well aware that a light surface scratch will not lead to failure on its own. That why I asked if the bars had been crashed.

 

Bars are however exposed to corrosive chemicals inour sweat and that can be a contributing factor.

 

The Scratch Bornman points out is inconclusive in my view since the picture is a little out of focus to be able to apportion blame soley on that.

 

There are other factors as well such as material weakness.

the area where the bar broke is also where the highest bending stress will be since at that point the bar could be considered to be a cantilever built into a wall (the stem). Aluminium tha has not be properly heat treated could work harden in that area, lowering the stress limit reducing fatigue life and lead to sudden failure. I've seen this in many thin walled aluminium tubes

[Capricorn]

Agreed , but i never said that that defect JB pointed out in itself will cause failure. As i clearly stated elsewhere, it's a combination of many factors.

 

The point of the discussion is that these types of failures invariably do begin with a defect in the material. The defects internal to the material we cant do something about really, until it manifests itself.?

surface defects such as scratches we can do something about, the easiest being prevention as opposed to redressing them.

[techguy]

Question is how long was it creaking before it suddenly snapped?

[Lotus]

How long have you had that bar for? and how long since

it was installed did it break? The rust on the inside of your stem bolts

suggests it's been a while since that bar has been removed.

 

I got it about two or three years ago from a friend' date=' in perfect condition at the time. I re-fitted it about 18 months ago, after rebuilding the bike. It was resprayed, but not heavily sanded for preparation. The lacquer overcoat may have hidden signs of cracking. The stem bolts aren't really rusted, that's more like oxidation (yes, I know that's really rust by another name ).

I checked the stem today, and there are no signs of protrusions on it, and no scars on the bar where it clamped in.

 

Here's the problem I think.

 

 

The circled area shows what I think could be a scratch, it is the

grey area between the black anodising and while aluminium.

 

Have a look and see if it is indeed a scratch?

 

No, that's just the original anodizing peeking out from under the lacquer overpaint.

 

 

The "evidence" is known as beach marks - typically these radiate

out from the initiation point (think a stone thrown in water and the

ripples radiating from it).

 

Have a look at the fracture face and see if you can spot the

initiatiion point and beach marks - that'll give you and idea of why it

broke. In bars I would sat the most common initiation point is a scratch

caused by the stem rubbing the bars' date=' a scratch made when cutting the

bar tape (as someone else stated) or an impurity in the alloy (worsenede

bt drawing the bars).

[/quote']

 

 

 

What I can see are two sorts of texture. Area A" has these radial striations, while area "B" has a grainy texture.

http://i157.photobucket.com/albums/t57/grahamr_photo/F430/IMG_1070v2.jpg

That area marked "C" has some interesting marks, which I've closed in on here:

http://i157.photobucket.com/albums/t57/grahamr_photo/F430/IMG_1071v2.jpg

It's not exactly a crack, but it's the only area with this "broken" texture.

 

Have you ever crashed or fallen with those bars in

the past?

How old are they?

I did go down once before - a wet road and the front washed out in a corner. Only apparent damage was to ego' date=' the bike was fine (I broke it's fall).

Whetehr your bars are Carbon or Aluminium, they should be replaced

at least as often as the manufacturer recommends.

I can't say I've ever seen such a recommendation, TBH.

 

Question is how long was it creaking before it suddenly

snapped?

Wasn't creaking at all (although I wish I could say the same for myself after that!). I keep the bike well serviced and tuned, and as noise-free as possible, and I notice things creeping up (well, most of the time).

 

I think the lesson from this (and the great comments) is that this area and the seat post should be treated with care. Treat scratches with HUGE suspicion, and replace if you're in any way nervous about the integrity of the part.

 

I've ordered the new bar and stem with oversize (38.1mm) centre section and a 4 bolt stem. The thing that really annoys me now is not the cost of the new bits, but having to buy new bar tape again, because I did this 3 months ago. I'm partial to the Fizik tape, and the price we pay here is ridiculous (compared to CRC). However, I plan to be riding again this weekend, so no time to waste.

 

 

[Capricorn]

 

hot damn guvnor. u take awesome snaps! ?Tempted to ask for a 360 degrees set of shots just like your last one, on both ends of the broken bar...

That definitely looks like something, and it probably been there since manufacture. But shadows can play tricks on the mind. What does the other face look like in that same area? Was that spot at the top or bottom, or where on the bar?

Capricorn2010-01-12 06:51:04

[GoLefty!!]

Looks like it simply fatigued . The smoother textureed area is stress cracing and the mopre rough areas is simply where the metal separated due to there being insufficient area to hold the load.

 

 

Not sure howlong your friend used the bar and if he/she crashed the bar prior to selling / giving it too you. But the crack could have been there before you got the bars. I'd slap the friend on the back of the head...

 

Easton recommends 5 yr replacement cycle for bars and stems,

3T similar.

Others say nothing which I view with suspicion.

[firewolf]

so maybe the cost of a torque wrench is not so bad after all? I don't as yet have one.  Always thought I must get one.  Especially with all the carbon tubes on seatpots, bars, etc.

[Lotus]

 

That definitely looks like something' date='

and it probably been there since manufacture. But shadows can play

tricks on the mind. What does the other face look like in that same

area? Was that spot at the top or bottom, or where on the bar?

[/quote']

 

The other face mirrors the marks exactly, right down to the tiny fissures you can see in the "C" area. The epicentre of the "C" is exactly at 3 o'clock, to the rear of the bar.

 

 

Easton recommends 5 yr replacement cycle for bars and stems' date='

3T similar.

Others say nothing which I view with suspicion.

[/quote']

Thanks for that. In future I'm marking these parts with expiry dates!

 

Johan, if you're following this, how hard should one tighten the stem bolts without using a torque wrench (or is that a vital tool to own)?

 

 

[firewolf]

a mechi at the place that I work explained that the average male hand will produce more than the required torque even when "toning" down the percieved required amount.  Especially SA okes right? I am aiming to get a torque wrench soon.

[ZakAttak]

Bars, stems seatposts Frames, etc are all mass produced mostly.... These various components are extruded and bent to form the desired shape (Bars, Seatposts)... During extrusion, if the aluminium is to hot, it will cause a bubbling effect between particles causing the material to be weaker at various points....Cracks are also formed when the material in not properly cooled down or by rapid cooling.... These issues are protected by Quality Assurance before made good for sale, but sometimes during Non destrucive testing (NDT), these issues pass, but the testing inevitably makes that particular component a bit weaker in lifespan.... Hence companies offer your various warrantees and guarantees on components... I say, if something like that did happen to you with whatever manufacturer, bring it to there attention as they would appreciate the feedback and find ways on improving on their NDT...

[firewolf]

this kind of equipment failure is super serious! It can be fatal!  And the fact that it happened with no warning is so damm dangerous.  If it were me I would make a very big deal about it.. letters and pics to manufacturer/dealer, letters to bike mags, etc. 

[GoLefty!!]

problem is the bars are 2nd hand and were repainted before he took ownership of them whch means the previous owner could have been a devious schmuck

[Lotus]

Truth be told, I was the one who painted the bars to improve their appearance after refinishing the bike. The bars were in pristine condition when I got them, but I felt they could look better by respraying a deep gloss black. There were no blemishes or scratches on them at the time.

 

As far as claiming against the manufacturer goes, I don't believe you can do that once you've substantially altered the component (and respraying certainly counts in that direction).

 

Fact of the matter is, I have to take responsibility for this. Either the respray contributed to the failure (unlikely in my opinion) or I failed to foresee that a  failing component would have a potentially serious result. That bar gave a number of years of good service, and I don't think Ritchey can be held accountable after that.

 

You live (if you're lucky) and learn. Ain't gonna make that mistake again!

 

 

[Capricorn]

well said lotus.

 

Nonetheless, one of the most interesting threads in a while I've followed on the hub. Big up to everyone

[Johan Bornman]

Truth be told' date=' I was the one who painted the bars to improve their appearance after refinishing the bike. The bars were in pristine condition when I got them, but I felt they could look better by respraying a deep gloss black. There were no blemishes or scratches on them at the time.

As far as claiming against the manufacturer goes, I don't believe you can do that once you've substantially altered the component (and respraying certainly counts in that direction).

Fact of the matter is, I have to take responsibility for this. Either the respray contributed to the failure (unlikely in my opinion) or I failed to foresee that a  failing component would have a potentially serious result. That bar gave a number of years of good service, and I don't think Ritchey can be held accountable after that.

You live (if you're lucky) and learn. Ain't gonna make that mistake again!

[/quote']

 

Dont be so hard on yourself. Respraying could have had no effect whatsoever. Period.

 

A component like that failing is not your fault. sh*te happens.

[Johan Bornman]

this kind of equipment failure is super serious! It can be fatal!  And the fact that it happened with no warning is so damm dangerous.  If it were me I would make a very big deal about it.. letters and pics to manufacturer/dealer' date=' letters to bike mags, etc.  [/quote']

 

The only big deal you can make of this is to cricitise people for buying the lightest stuff on the market. This culture of asking how much something weighs instead of how strong it is, is Darwinian.

 

We see this all the time. Someone sells something, someone else wants to know what it weighs. This flows back to the manufacturers who are under pressure to produce the lightest stuff possible.

 

I've had a 3TTT bar once that, in the fine print, said it should not be used for more than 3 years. 3 Years? Give me a break...bad choice of words. Give me a stronger heavier bar please.

 

Saving weight has consequences, yet no-one points a finger that way. Just like half earth's problems are over population, the concept wasn't even discussed at Copenhagen. The blame has to lie elsewhere.

 

Letters to bike mags? 'Cmon. They'll simply bad-mouth one brand or vehemently stand behind it (if it is an advertiser). They will not address the root problem of making handlebars from half a coke can.