Well this is controversial

[albion]

Probably because it's very, very thick in section or possibly even solid.. unlike a bike frame. Are the impact surfaces bare composite or faced with something else?

And why high end frames are generally too delicate for us earth dwellers.

 

[Venod]

They are designed to be clamped, that is how they stay in place in the seat tube

Yes with a clamping force of 5 or 6 Nm, is that enough to support a complete bike ? I think caution is the watch word if you have to clamp it.
When clamping the stem to a carbon steerer a insert is fitted for a reason, and with it fitted the clamping force is still minimum.

 

[T4tomo]

Probably because it's very, very thick in section or possibly even solid.. unlike a bike frame. Are the impact surfaces bare composite or faced with something else?

Solid? are you having a giraffe, its hockey stick not a fecking sledge hammer.

Don't get me wrong they do occasionally break, just as wooden ones did back in the day. bare composite btw. They will be thicker walls than say the top tube on a bike, but probably similar thickness as the BB shell are and laid up with multi -directional fibre and there is usually some internal ribs in key impact areas.

The point is you can make very strong stuff out of CF, just as you can with steel and Alu, its all in the skill of making.

I have bikes made out of all 3. Horses for courses.

 

[wafter]

I suspect it wouldn't do it a lot of good also if you were in the sort of crash where it hit something solid and pointy with a side-on impact to the tube(s). But those types of crash are not common for road cyclists.

Indeed; however it's just the sort of impact that might be encountered if the bike's leant against something and falls over, or something falls against it during storage or transport..

 

[Dogtrousers]

You're absolutely correct that we don't see composite forks "breaking in droves" however I firmly believe that they're subject to a significantly higher failure rate than steel, while impending failure is a lot harder to detect and prevent. While certainly not an epidemic, if you look there are plenty of horror stories on the net about composite fork failure; many of which have resulted in serious injury or death.

This is something that actually interests me.

In 2020 I crashed my (steel) bike badly on a pothole. The front wheel was no longer a wheel afterwards. I forget how many spokes were broken but it was a lot. The rim was totally mashed. The fork, which is carbon, still looks fine and can't see any problem with it. I've ridden it for 4 years since but it still nags at the back of my mind. I may replace it some time, but probably like-for-like.

I've been wasting my time on cycling internet groups for far too long, and while I've seen dozens of broken cranks and cracked Ti frames and a fair few broken handlebars stories I don't recall any broken carbon fork stories (apart from the notorious Viscount Death Forks, but they're more for historical interest). Not saying there haven't been any, I just don't remember any.

 

[Punkawallah]

I stopped for a broken carbon fork. He already had a mate with a van on the way - was fine. But one ‘broken carbon fork story’, at least.

 

[Punkawallah]

To be honest, if I was buying a bike right now, the question of how well my bike would withstand a big thump in 120 years time would not be of any importance to me at all.

Wot? No ambition? Keep having birthdays - it’s a proven fact that the more birthdays you have, the longer you live!

 

[ColinJ]

I don't recall any broken carbon fork stories

Cannondale issued a recall notice on the version of CAADX that I own after several fork failures including one which led to the death of a rider. They said that tests did not reveal a problem but they were doing it to be on the safe side...

 

[Dogtrousers]

Cannondale issued a recall notice on the version of CAADX that I own after several fork failures including one which led to the death of a rider. They said that tests did not reveal a problem but they were doing it to be on the safe side...

Yes but I'm not recalling having seen any "my fork failed" stories. Unlike, say cranks - crank failure stories are ten a penny.

If course this might be a survivorship bias thing. Everyone whose fork fails ... dies

 

[albion]

www.google.com/search?q=%22my+fork+failed%22

 

[Alex321]

Yes with a clamping force of 5 or 6 Nm, is that enough to support a complete bike ? I think caution is the watch word if you have to clamp it.
When clamping the stem to a carbon steerer a insert is fitted for a reason, and with it fitted the clamping force is still minimum.

I think the clamping force on a bike stand is less than 6Nm, but difficult to be sure since it doesn't use the type of mechanism you can check with a torque wrench.

With my bike, that doesn't actually matter, since it isn't a carbon seat post.

 

[srshultz]

For your consideration. Assume for purposes of discussion that there exists a bike manufacturer that can make 4 identical bikes. They all have the same geometry, aerodynamic features, weight, group set, etc.. The only difference in each bike is the frame material of construction. The materials are steel, CF, aluminum and titanium. They are also, priced the same.
Which one would you buy and why?

 

[Alex321]

For your consideration. Assume for purposes of discussion that there exists a bike manufacturer that can make 4 identical bikes. They all have the same geometry, aerodynamic features, weight, group set, etc.. The only difference in each bike is the frame material of construction. The materials are steel, CF, aluminum and titanium. They are also, priced the same.
Which one would you buy and why?

Ell that isn't actually possible, as the materials don't weigh the same.

But assuming it was possible, I would probably choose CF based on what I have ridden, because of the ride feel. But I have never ridden Ti, and I believe that has some of the same ride qualities. And TBH, I don't really remember what steel felt like, it was so long since I last rode a steel framed bike.

 

[Venod]

For your consideration. Assume for purposes of discussion that there exists a bike manufacturer that can make 4 identical bikes. They all have the same geometry, aerodynamic features, weight, group set, etc.. The only difference in each bike is the frame material of construction. The materials are steel, CF, aluminum and titanium. They are also, priced the same.
Which one would you buy and why?

Having had 6, (still have 2) Ti bikes, I would chose Ti, I have no problems with any of the other materials, but Ti in my experience is much easier to look after, no paint to worry about (assuming you have a raw frame) wipe it with a damp cloth it looks like new and a strong material to take a knock or two.

 

[T4tomo]

Don't clamp a carbon seatpost.

The advice is, when using a bike stand, clamp the seat post not the carbon frame. If this is an alu seatpost its obvious why.

But also a carbon seat post is significantly stronger than the carbon frame, particularly the top tube which is likely candidate to clamp, as it is (usually) circular cross section and thicker material than the frame tubes, as it needs to support the slight flexing with the riders weight.

The guidance to only tighten a seat post bolt to 5Nm is to prevent damage to the seat tube (at the clamp area) not the much stronger seat post