Bicycle Mechanics - How tough is carbon?
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02-19-04, 09:44 PM
I was cleaning my new bike frame today and noticed a couple tiny spots that were just like no bigger than large pin prick size nicks in the surface of the frame. Now I wouldn't think this would cause any problem but it made me wonder at what point would a nick mater? What dept? and can a nikc spread to a crack or is there any treatment for the surface of a damaged area? These questions are what encouraged me to make my first bike a ti bike. But I the ride of this bike made it seem worth the risks. Or maybe Im just parnoid.
02-19-04, 10:39 PM
The outer layer on carbon bikes isnt the actual carbon. Its a layer of pretty looking 'carbon' stuff bascially, Im pretty sure at least. The small nicks should be fine. Going back to my materials class last semseter, failure would come from a small nick in the actual carbon fiber and over repeating stressings it would enlarge and eventually fail.
02-20-04, 06:12 AM
Cleveland, If I remember correctly you bought a 5200. I have the same bike and had similar worries when I bought mine. Nicks are nothing to worry about. Its when you start to get into major gouges that you start to have some concern. No matter what though, as long as you are the original owner of the 5200, Trek has a lifetime warranty on the frame.
Agree small nicks don't matter. When a gouge gets into the carbon fiber layer, that could be a problem, depending on the loads at that location.
Concerning warranty, Trek's lifetime warranty is for manufacturing defects in materials and workmanship. It doesn't cover wear and tear, or fatigue (wearout) of the frame. Trek excludes failures caused by your damage or abuse of the bike, just like anyone else in the business.
02-20-04, 01:17 PM
Carbon fiber is weird stuff. It can be absolutely indestructable at one spot, and then another it can shatter like a crystal wine glass hitting the floor. It is tough stuff, and most likely you wouldn't be doing crazy downhill stuff on a carbon frame. It is stiff, therefore it doesn't take tremndous pressure well. I doubt a small knick is enough to shut you down, but that could lead to cracking eventually. Just keep an eye on it.
02-20-04, 01:47 PM
The beauty of carbon fiber material is that you can make it strong in the direction you want. This is accomplished by using different layers fibers and arranging them in a pattern that gives maximum strength in the directions you want. You can go in depth into the subject but we don't need to. Since carbon is quite stiff it transfers power well, but you lose elasticity or the ability to bend without breaking. So on a steel or aluminum bike, a tube with bend, dent or somehow deform before it reaches the breaking point. Carbon fiber fails catastrophically or in other words, you ride along and all of sudden Kablooey! But that is extremely rare.
As for the original question, don't lose sleep over it. Periodically check them. Other places to look out for signs of damage is joints and especially where metal meets the carbon. At these points you can have things unglue. Hope this is of some use or at least mildly interesting.
My TCR1 has 3 holes (factory) drilled into the bottom bracket area to allow water to drip out of the frame, so a few small nicks shouldn't cause any problems.
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