How to tell if carbon frame is knackered

[Yellow Saddle]

Forks ? how do you know the forks are ok ? Cracks between the crown and steerer ?

Fork (singular)? That's the easy one. The most stressed area is the transition between crown and steerer. Remove the fork, and place the steerer horizontally in the vice so that the smooth section below the jaws clamps it reasonably firmly. Now manipulate the fork blades and watch and listen to what happens at the transition area. You can change the plane once and you'll be sure of the fork's integrity, as they say.

However, in this case the bike was it from the side and the fork escaped any strain.

But, I buy your statement about unease. That's a one for the psychologists, not mechanics. It took me years to half master my fear of sudden stem failure after such an incident with a friend riding alongside me.

 

[jefmcg]

Well, one way to be sure is to keep riding it. If it doesn't catastrophically fail at some point while travelling downhill at 70kph, then the frame is ok.

 

[ayceejay]

If in doubt
chuck it out

WD Yates

 

[ufkacbln]

Not really. Steel cracks with fatigue and the cracks happen slowly and usually manifest suddenly. In a rear-end, it would have bent and dented.

I preferred Sapphire

 

[DTD]

Thanks for all your help.Looks like if there's any doubt, get a new bike.

 

[Tom B]

There are a couple of UK based carbon repair specialists of which one is http://www.carboncyclerepairs.co.uk/index.html

I dare say if you contact them they will do an insurance inspection and report - for a fee.

Probably a question they will have been asked before.

The insurer may pay this especially given the LBS's report ask them before proceeding.

 

[Pumpkin the robot]

My carbon framed bike was involved in an accident. 30mph into the side of a car that pulled out in front of me. I contacted several places about having it ultrasonically tested (not x rayed) One of them basically said in an impact of that speed if there was damage to the frame you would know about it, there would be cracks. He said he would be 99% certain that the frame was ok if there was no cracks in the paint or visible cracks.Over 5000miles later and I trust his observation. The bike came out of the crash better than I did, thats for sure!
I will be claiming for a new bike as the LBS wrote the bike off because of the impact, but I am happy to carry on riding it.

 

[Winnershsaint]

Almost three years ago I was cycling home on the last day of August having dropped my car off for a service. Blinded by the sun rising above the rooftops close to my house I clipped a stupidly parked car with the front end of my bike at about 17 mph , turning the front wheel into a pringle and sending me over the bars to crash down on my right shoulder. An eyewitness said that only when I'd hit the deck and the bike was above my did it separate from my cleats sending it catapulting and bouncing into a cul-de-sac where it came to rest in a bush. Bike was unmarked, carbon was not visibly damaged, but the wheel was totalled. I had concerns about the effect the impact had on the front end, particularly the forks and steerer, but like the above poster was told that if there was damage to the frame it would by visible in the form of cracks. LBS also wrote the bike off, but I have ridden many thousands of miles on it since and have been quite happy to do so. The bike was unscathed, me less so. It was three months before I returned to work.

 

[ayceejay]

This insurance malarkey is a mystery to me, I have never come out on top.
But a friend of mine had her Volkswagen Beetle parked outside her house, the street was on a bus route and one day a bus hit it and the insurance company wrote it off. She continued to drive it and a week later a bus hit it again and (don't ask me how or why) the insurance company wrote it off again and she continued to drive it. I don't know the amount of money involved.

 

[Big Dave laaa]

Claim for a new bike then see if you can buy the old one back off the insurance for a nominal fee.

 

[Svendo]

Claim for a new bike then see if you can buy the old one back off the insurance for a nominal fee.

In my experience this isn't necessary, the broken bike is written off by the insurers and they have no interest in collecting it. Presumably as there's no scrap value unlike a car for instance.

 

[User33236]

In my experience this isn't necessary, the broken bike is written off by the insurers and they have no interest in collecting it. Presumably as there's no scrap value unlike a car for instance.

+1 I got paid out for my bike following an accident and there was never any mention of rhe third party's insurers being remotely interested in the 'written off' bike.

As an aside. The LBS does not and cannot 'write off' a bike that decision is purely down to the insurance company based on the report it receives (the report can of course influence their decision)

The insurers 'wrote off' my bike simply because the report stated that there was damage to the dropouts on the front fork and that, after speaking to the manufacturer, replacements would not be available for over 6 months.

 

[lpretro1]

You don't x-ray carbon - you have to use ultrasound to check it out

 

[Drago]

What all this "you'd see the cracks" malarkey? Unless you can do some kind of shrinking act and climb inside the frame for a nosey with a suitably miniature miners lamp, then how will you know if there are any cracks?

 

[Yellow Saddle]

What all this "you'd see the cracks" malarkey? Unless you can do some kind of shrinking act and climb inside the frame for a nosey with a suitably miniature miners lamp, then how will you know if there are any cracks?

A crack in a frame starts at the surface. The surface is smooth and usually covered with lacquer, gel coat or paint. Paint does not stretch and reflects the cracks inside. It is very easy to see. Further, if you manipulate the joints, the crack opens and closes. You can see it. No need for a miner's lamp and a dwarf.