Snapped Chain Stay Roubaix SL2

[WindyRob]

not me but i want to respect his wishes. If it was me i would be banging doors wanting a demonstration how removing 2 chainlinks can cause such a force as to snap the frame, once i had seen evidence then i'd think about accepting the decision. Frankly a quick google shows multiple frame failures by many different bike companies, some through impact but others completely unexplained; it's not unknown.

Personally i'd be asking them to prove that there wasn't a defect in the carbon itself. This bloke spent £1000's to raise money for kids in Burundi (see bike for burundi) what would a few £100's be to a company the size of Secialized.

 

[Shaun]

If Specialized do offer him a deal and the result is posted here then won't that be a positive result for both of them?

And I don't think Spesh have anything to worry about in terms of their reputation; I think you'll find most Spesh owners here have nothing but good things to say about them (me included - I've got two of 'em myself ... )

I don't mind deleting it if it will definitely scupper his chances of a favourable outcome, but it can often be good to see these real-world threads because it show companies in a good light who are willing to go the extra mile or meet you half way in putting things right.

See what he thinks and let me know.

Cheers,
Shaun

 

[oldfatfool]

In all car warranties there is a clause saying any modification will void the warranty. This to me is like a car company refusing to replace a blown engine because the car as been run on 18" wheels instead of 17's and the force required to turn the extra diameter as caused the failure.

In fact I would be asking Spesh to point me to the part of their literature that states the bike must be run using a chain of xxx links.

 

[black'n'yellow]

I'd like to see a few more pics, ideally - damage like that must have caused some corresponding damage on the other side of the bike...?

 

[fossyant]

I'd like to see where the rear mech is big ring, big sprocket

 

[GrumpyGregry]

I'd like to see the CCTV of that bike being shipped from factory to shop, from shop to home, from home to airport, from airport onto plane, off plane to US airport, from airport to hotel and every step in between....

...but good on spesh.

 

[WindyRob]

IMHO it's not that good a deal, but he's not me.

Shaun, I'll ask him tomorrow about this.

Rob

 

[Mr Celine]

ISTR that tubes fail in compression at an angle of 45 degrees to the applied stress. But it's a long time since I did any engineering and I've no idea if CF fails in the same way as metal tubes.

 

[the snail]

In fact I would be asking Spesh to point me to the part of their literature that states the bike must be run using a chain of xxx links.

I expect it doesn't tell you not to throw the bike off a cliff, but I wouldn't expect them to replace my frame if I did that. If you need to shorten the chain, surely the thing to do is adjust the gears so you can't select the biggest gears? To me the failure in the photo looks consistent with what Specialized said, it doesn't look like it failed in normal use.

 

[Rohloff_Brompton_Rider]

this is exactly what i expected from the op's post and mickle's and record's input, plus my own engineering experience...oh and my £5k carbon bike snapping busting my wrists and eye socket.

the force comes from the rotating mass and centrifugal force of the spinning cranks and rotating mass of the chainset.

the wheel bearings seize under the loads exerted from rushing up the block, assuming an upcoming ascent from a decent descent (why else be on large/large?) causing an attempt at an abrupt stop when going l/l. this force effectively turns the bike into fixed gear for a very small period of time. the tyre friction to road surface comes into play, which tries to keep turning the wheel but the chain's too short, so nature shortens the chainstay to fit the chain by crumpling it (by using the chain as the bow string and the chainstay as the bow in effect).

EDIT: this also explains why the rear didn't fail, it did it's job in the linear axis and flexed in the axial axis.

EDIT AGAIN: and as record stated carbon is not isotropic and the way it's woven / layered up depends on where the material can handle stresses. in a chainststay i'm guessing torsional and longitudinally but not tangentially.

if you disagree, go and lay your nice carbon bike on its side and let colinj or me stand on the middle of your chainstay and do a belly dance waving our nipple tassels around.

well that's what i reckon anyway.

 

[black'n'yellow]

this is exactly what i expected from the op's post and mickle's and record's input, plus my own engineering experience...oh and my £5k carbon bike snapping busting my wrists and eye socket.

the force comes from the rotating mass and centrifugal force of the spinning cranks and rotating mass of the chainset.

the wheel bearings seize under the loads exerted from rushing up the block, assuming an upcoming ascent from a decent descent (why else be on large/large?) causing an attempt at an abrupt stop when going l/l. this force effectively turns the bike into fixed gear for a very small period of time. the tyre friction to road surface comes into play, which tries to keep turning the wheel but the chain's too short, so nature shortens the chainstay to fit the chain by crumpling it (by using the chain as the bow string and the chainstay as the bow in effect).

EDIT: this also explains why the rear didn't fail, it did it's job in the linear axis and flexed in the axial axis.

EDIT AGAIN: and as record stated carbon is not isotropic and the way it's woven / layered up depends on where the material can handle stresses. in a chainststay i'm guessing torsional and longitudinally but not tangentially.

if you disagree, go and lay your nice carbon bike on its side and let colinj or me stand on the middle of your chainstay and do a belly dance waving our nipple tassels around.

well that's what i reckon anyway.

That's a remarkable piece of conjecture - a good entry for the Turner prize on bicycle-related creative writing..

So, all that happened as you say - and the hanger didn't fail and the mech didn't snap first..?? I'm particularly interested in why the wheel bearings would 'seize' simply because of some rapid downshifting..??

 

[mickle]

- and the hanger didn't fail and the mech didn't snap first..??

A too-short chain will place no additional loading on hanger or mech than a chain of the correct length.

 

[black'n'yellow]

A too-short chain will place no additional loading on hanger or mech than a chain of the correct length.

come on - think about it....

The chain has been shortened by two links, we already know that, so the mech is already being pulled tighter than usual. Let's assume the guy was in 50/18 and the chain is now very tight and the mech is at full stretch. Let's then assume he tries shifting into 50/25 - what happens..?

 

[Andrew_P]

I can say for certain that a short chain will at least really stretch the rear mech, when I changed from 5600 RD to 5700 the chain from the 5600 was too short and big front trying to get up the cassette the RD was stretching out I would be fairly confident had I forced it the hanger at least would have bent to take the stretch, not sure on the RD didn't want to try. The picture looks like a right to left bend/compression?

 

[dan_bo]

if you disagree, go and lay your nice carbon bike on its side and let colinj or me stand on the middle of your chainstay and do a belly dance waving our nipple tassels around.

well that's what i reckon anyway.

How's about you AND ColJ?

Can I wash my brain please?