Road Cycling - Carbon vs bitumen

Anyone ever crashed a carbon bike?

I'd like to know how the bike came away from it. Any cracks or chips?

I was told that if you have a half decent crash with carbon, chances are the bike is going to be f-cked. And if the lacquer coating is damaged and water penetrates the carbon it is also f-cked.

Thanks

whoever told you that has no clue

carbon fibre is strong - Ive crashed on my 5200 several times. There are instances where a CF bike broke up and shattered after a particularly hard crash, but the same circumstances with a alum frame will likely result in cracked tubing, broken welds, etc...

Let's not forget, before CF became popular on bicycles, they were used in aviation. Now.. if CF was THAT weak... you think anyone would trust it on an aircraft surface like rudder? What if the damn thing shattered!!!?

Crash dependent. And then a gamble.

CF could be just fine, but it is subject to micro cracks that can cause it to become very weak, and you can't see it. When the actual fibers matrix is compromised, you end up with a weak part. Bikes don't used the same number of layers of carbon cloth that boats and planes use, so there is less margin for error (but also less loads). Crack that let in water subject the fiber layers to delamination from temperature changes. I've seen that a lot. Delamination = short life span and serious strength issues.

I've got one crash on my carbon (5200 frame) that was a high speed skid out on a wet road. Skip and tumble. I've got 2500-3000 miles since that. If I actually cracked the carbon, then I probably would have replaced it. I also race on "high-performance" sailboats with lots of carbon. Even the beefy stuff can just blow if there are enough micro-cracks you can't see... looks and sounds like someone put a charge in it an blew it to pieces. The scary thing is that it isn't usually expected. Do you want that at 20mph on a turn where you think nothing of it? What about 40 when there are some good loads?

So, is you bike toast? Hard to tell. I think that the same crash on an aluminum bike or a Carbon bike will damage the tube to the point it can't be fixed. Neither can be re-bent. Steel (and I think Ti can all be bent back with material integrity).

Last point - post crash, go to the LBS and see what they think, and what they think it means to the warrantee.

>>Now.. if CF was THAT weak... you think anyone would trust it on an aircraft surface like rudder? What if the damn thing shattered!!!?

You mean like the Airbus 800, American AirlinesFlight 587 in Belle Harbor, New York Nov 12, 2001. Pilot mis-training caused the tailfin to be over-stressed. It cracked and fell off, leading to the loss of 265 lives.

A steel or Ti frame that is crashed might be fixed, but depending on the crash, tubes could be replaced. The way a trek or kestrel is built, tubes cannot be replaced. Some cf builders could replace cf tubes, like calfee. I think most builders and trek will not warranty a crash. I think kestrel has a replacement program that will replace a crashed frame for a nomial price, not sure about trek. :p

A steel or Ti frame that is crashed might be fixed, but depending on the crash, tubes could be replaced. The way a trek or kestrel is built, tubes cannot be replaced. Some cf builders could replace cf tubes, like calfee. I think most builders and trek will not warranty a crash. I think kestrel has a replacement program that will replace a crashed frame for a nomial price, not sure about trek. :p

Actually, Trek tubes can be replaced. They use a lugged carbon frame and can take out certain portions of the tubes. However, the cost is pretty high for the delamination and whatnot.

Anyone ever crashed a carbon bike?

I'd like to know how the bike came away from it. Any cracks or chips?

I've crashed my CF MTB quite a number of times... some rather spectacularly too might I add. I've only come away with clearcoat scratches though.

I only had one big crash with my CF roadbike. My riding partner (actually the owner of the shop I bought the bike from) was errr... distracted by scenery... and drifted into me while we were doing about 25MPH. I almost managed to stay upright. He hit me from the right and slid back where his front wheel then proceeded to contact my rear and he wiped out. In the process he swiped my rear end out from underneath me. we both went sliding across the road and ended up on the opposite side in the ditch. I had some road rash as did he. I lost a barend plug and there was a little tear at the end of my bartape. We inspected my bike. The frame, fork, handlebars, seatpost and cranks all checked out fine. I even used a resistance test (with an ohmeter) to make sure there weren't any hidden cracks. My frame's manufacturer also has a pretty generous lifetime crash replacement policy.

>>Now.. if CF was THAT weak... you think anyone would trust it on an aircraft surface like rudder? What if the damn thing shattered!!!?

You mean like the Airbus 800, American AirlinesFlight 587 in Belle Harbor, New York Nov 12, 2001. Pilot mis-training caused the tailfin to be over-stressed. It cracked and fell off, leading to the loss of 265 lives.

which btw - would have happened to an alum body just the same if the pilot went over the design specifications.

which btw - would have happened to an alum body just the same if the pilot went over the design specifications.

Exactly. Airframes are built and tested and there are definate stated design limits which should the PIC exceed will result in a situation where "all bets are off." This is the case with any airframe material. According to the NTSB...


Composite Lug Test

On August 13, 2003, the NTSB conducted a lug sub- component structural test at the Airbus test facility in Hamburg, Germany. Engineers from the NTSB, Airbus, American Airlines, BEA, and the NASA Langley Research Center supported the testing and analysis.

The test component was a rear main attachment lug from an A310-300 Carbon Fiber Reinforced Plastics (CFRP) fin box skin panel. The panel was originally constructed as a manufacturing quality test article and was used to demonstrate the interior quality of the skin panel.

The test was to demonstrate the behavior of the lug under a load condition similar to that experienced by American Airlines 587 during the accident flight. The load condition used was derived from the flight data recorder information and the subsequent structural finite element analyses.

During the test, the lug structurally failed at a load beyond its design ultimate limit. The test failure appeared to be consistent with calculated failure load analyses performed by both Airbus and NASA Langley. Work is continuing at the Safety Board to continue refining a reliable estimate of the loads on the AA587 fin during the accident.

The Safety Board has obtained two other lugs for testing. Two rear lugs were removed from the tail fin from the A-300-600 aircraft that was involved in a loss-of- control incident in 1997 as American Airlines flight 903 (see Fifth Update, February 25, 2002). These lugs will undergo structural tests in December of this year and February 2004 in Hamburg.

Clearly the test structure was able to sustain integrity throughout its design parameters but failed at estimated loads that were derived from the accident conditions. Of course this is a recreation and no one yet knows what exact level of loading was actually imposed on the actual failed structure.

If I take an aircraft regardless of construction material and started bouncing it around beyond well beyond the stated Vno or throttle it up through Vne such as attempting a recovery from an ultra-steep dive then it would not be highly surprising to induce structural failure.