Ad nauseum, life of composites

[Brucey]

I don't know how commonplace it is that people adhere to the manufacturer's recommendations about anything TBH.

Maybe if more people did, there would be fewer failures?

cheers

[reohn2]

I don't know how commonplace it is that people adhere to the manufacturer's recommendations about anything TBH.

Maybe if more people did, there would be fewer failures?

cheers

And few people buying a second CF frameset perhaps

[Dave W]

So every mountain bike that does a drop off gets replaced Monday morning? Every Carbon cyclocross bike that crashes over a bump is replaced, every tdf bike is replaced on every crash? Every Sportiff bike that hits a pothole has the forks and frame replaced every weekend? Get real. You still haven't shown us all these failures either.

[Dave W]

By the way, two of my carbon bikes that never imploded were second hand

[andrewjoseph]

A friend of a friend on facebook just posted up that he'd broken his 4 th carbon frame.

[Dave W]

Yes, my uncles dads brother in law's boss's son just broke a steel frame too.

They all break (steel, carbon aluminium if you abuse them hard enough) wonder why he keeps riding carbon then? Must be mad.

[andrewjoseph]

I've no idea why he sticks with carbon, I don't personally know him. Maybe he has loads of money and is happy to spend it. Maybe he prefers the ride and is willing to put up with the limitations.
Maybe he is just blinkered.

Do a search on facebook, you might find him and ask him yourself.

His name is mark Harding.

[Brucey]

So every mountain bike that does a drop off gets replaced Monday morning? Every Carbon cyclocross bike that crashes over a bump is replaced, every tdf bike is replaced on every crash? Every Sportiff bike that hits a pothole has the forks and frame replaced every weekend? Get real. You still haven't shown us all these failures either.

missed the point again.... RTM! If the front wheel got flatted in any of those (by say a 10-20G impact) then the frame/fork may well have been overloaded. Then you have to use your judgement and/or inspect the thing, or simply bin it, if you want to be properly safe, as per the manufacturer's recommendations. If it were an aircraft (after say a heavy landing) if would be banned from flight pending an inspection, and if it were a critical racing car component it would be a scrap bin job for sure; those guys go through CF wishbones like they were toothpicks.

By the way, two of my carbon bikes that never imploded were second hand

would you buy secondhand tyres? It is closer to that than you might like to suppose, except tyres give you more warning before they let go...

cheers

[Dave W]

What do you think a second hand car comes fitted with? Think about it.

[Brucey]

well it doesn't come fitted with used bicycle tyres....

cheers

[tim-b]

Hi

@[XAP]Bob
Thanks for the warranty run downs

Is one make of CF frame going to have five times more longevity than another?
Is a steel frame from one manufacturer going to last five years and a lifetime from others?

I think we all accept that isn't what manufacturers are driving at with their warranties, and we all know of plenty of examples of way older frames in all materials

As for the Specialized 250lb (113kg or almost 18 stones) warranty, CF can be engineered to do whatever the designer wants (within reason). If you make it stronger it becomes heavier/more expensive

I think that you can throw that particular red herring back

Regards
tim-b

[tim-b]

Hi
Brucey said

I also note that the overload which is required to (say) create a radial dent in a front wheel will also create exceptionally high stresses in a front fork and frameset too; very likely these stresses are instantaneously far in excess of the 'normal' service stresses for which the parts are designed; (many wheels will take between 0.5 and 1 tonne radially before they get stoved in, but it varies with the shape of the surface the wheel bears against). It may well be that if you (say) run through a bad pothole that flat spots your front rim, you should think about binning your CF fork/frame too.

Decades ago, as a teenager, I took part in the Three Peaks Cyclo Cross (I won't say "competed in" )
I was on a 531DB frame/fork with sprint rims and cyclo cross tubs. I hit something and came off quite spectacularly, once I'd worked out which way was up and found my bike I could see that both the frame and fork were bent to the point that the front tyre almost touched the downtube. The front wheel was undamaged.

If you hit something with that sort of force, whether you stove the wheel in or not, you're coming off, and your frame material won't matter

Regards
tim-b

[[XAP]Bob]

Hi

@[XAP]Bob
Thanks for the warranty run downs

Is one make of CF frame going to have five times more longevity than another?
Is a steel frame from one manufacturer going to last five years and a lifetime from others?

I think we all accept that isn't what manufacturers are driving at with their warranties, and we all know of plenty of examples of way older frames in all materials

As for the Specialized 250lb (113kg or almost 18 stones) warranty, CF can be engineered to do whatever the designer wants (within reason). If you make it stronger it becomes heavier/more expensive

I think that you can throw that particular red herring back

Thanks to Brucey for giving me all the links.

The "red herring" is the only mention of rider weight (other than CB, who suggest an all up limit of 120kg across all their bikes). The warranty does imply expected lifespan to some extent - obviously some examples will massively exceed the warranty, but this is a "lower limit" on life, which you can expect from some high percentage of frames.

[Brucey]

Decades ago, as a teenager, I took part in the Three Peaks Cyclo Cross (I won't say "competed in" )
I was on a 531DB frame/fork with sprint rims and cyclo cross tubs. I hit something and came off quite spectacularly, once I'd worked out which way was up and found my bike I could see that both the frame and fork were bent to the point that the front tyre almost touched the downtube. The front wheel was undamaged.

If you hit something with that sort of force, whether you stove the wheel in or not, you're coming off, and your frame material won't matter...

In that case you knew the frame and fork had seen an overload because they were bent. In this instance they saw an overload before the wheel pringled. Had it been a CF frame/fork then it might have been the wheel that failed first, but at a higher force (you might have had a worse accident, too; I've been grateful for frames and forks that 'melted into the ground' in a bad prang ).

A CF frame isn't designed or tested to see loads that high either. Unfortunately there is a range of loads which can cause internal damage in a CF structure but leave little or no external sign of damage. Once CF structure has seen loads like that its fatigue life can be compromised, and it may break subsequently with little or no real warning.

That is the reason for the manufacturer's comments about the possibility of hidden damage following an overload, with the recommendation in many cases that the part is simply replaced.

Note that the peak force can be very high in an impact situation (e.g. running over a small kerb) and it won't throw you off the bike or anything; the peak force in the frame is only weakly related to what happens to the rider, or how bad the prang appears to be.

My suggestion was that if the wheel had been stoved in radially, you should definitely be concerned about the possibility of such an overload having occurred. In reality this isn't infallible; if you use very strong wheels and happen to hit a nicely curved rock or something, (perhaps as you did) the wheel mightn't see any damage even at loads high enough to be of concern to the frame and the fork.

With some materials the damage arising from overload is fairly obvious, with others it isn't.

cheers

[reohn2]

Following on from Brucey's post,(----***anecdotal story alert***-----).
Some 6 years ago I stupidly ran into the back of another tandem on our tandem at a probable impact speed of mid teens MPH.
I went OTT followed by Mrs R2 the other couple we shunted onto the grass verge,I skinned my knees Mrs R2 big bruise on her thigh.My pride severely dented and felt like a fool
Both bikes(steel)were surprisingly unmarked but on further inspection when we got home I found although the front wheel(48 spoke) was straight one spoke had a slight kink,but the axle was bent very slightly.I removed the forks and checked them and the frame thoroughly for any signs of damage as to my mind it takes a lot of energy to bend a wheel axle when in the frame.
No damage found,a new axle and spoke fitted,tyre wheel and rim thoroughly checked,no further damage.
We've been riding the same bike confidently since without issue.
CF in the same situation could quite easily have been damaged internally without any signs,whereas I feel sure there'd be signs paint crinkles,weld cracks etc,with a steel frame and fork.