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Carbon vs. Titanium frame: life expectancy?(15 posts)

Carbon vs. Titanium frame: life expectancy?fbg111
Sep 17, 2002 2:37 PM
I was just at my lbs, checking out some of the new carbon Treks and Giants, and asked a sales guy what kind of life expectancy a carbon frame has relative to Titanium, Alum, and Steel. He told me that carbon and Ti are the two longest lasting frame materials, which surprised me b/c I didn't realize carbon was such a long-lasting material. Is that true?
Can you define frame life expectancy for me? (nm)Spoke Wrench
Sep 17, 2002 2:51 PM
re: Can you define frame life expectancy for me? (nm)tao
Sep 17, 2002 3:05 PM
Radioactive decay, carbon half-life?
Can you define frame life expectancy for me? (nm)fbg111
Sep 17, 2002 3:44 PM
For instance, with enough wear and tear, will a carbon frame start getting stress fractures, become less stiff, or become more prone to failure? How about Ti? Thanx.
Sep 17, 2002 3:19 PM
..."normal" riding conditions, a "respectable" amount of maintenance, and no crashes, I think that you would get "bike lust" before either frame would wear out given they were well-built. I had a Merlin Extralight for 9 years and that frame was nowhere near the end of its life expectancy. I got a new bike simply because I wanted something new.
Good to know. Thanx. nmfbg111
Sep 17, 2002 3:49 PM
re: Carbon vs. Titanium frame: life expectancy?irregardless
Sep 17, 2002 3:26 PM
Lots of 8 year old Kestrels still on the road. I see them every day.
re: Carbon vs. Titanium frame: life expectancy?Lactate Junkie
Sep 17, 2002 3:51 PM
All high end bikes, Carbon, Ti, Steel and even Aluminum will probably last longer than you will want to keep them. The caveat to this is some of the ultra light aluminum and steel bikes that tend to be pretty disposable. Here is a good rule of thumb for steel and aluminum. If the frame weight less than 4lbs for steel and 3lbs for aluminum (in a mid sized frame 56-58cm) it is very light and may have long-term durability issues. There are always exceptions, but it is a good general rule. Done properly, composite and Titanium bikes will last longer than either steel or aluminum, but you are talking decades of use here not years. Don't worry about it too much. If you are spending high-end bucks most of the bikes out there will last "forever".
Too many variablesKerry
Sep 17, 2002 4:09 PM
Clearly Ti and steel have the most going for them in the longevity race, but there are way too many variables to make a prediction. You have all kinds of issues on the rider side, not the least of which is weight, but also riding style, road conditions, rider strength, etc. Then on the frame side there are all the issues of the specific alloy, tube wall thickness, frame design, and the actual construction. In reality, there are very few riders who will put enough miles on a frame of any material to wear it out or cause failure. However, there are enough so that you will hear about it. Today's superlight Al frames will not last that long, nor will a CF frame designed to be as light as possible. Ti and steel won't fare much better, but at least they are not likely to fatigue fail.
Too many variablesfbg111
Sep 17, 2002 4:33 PM
I thought steel and Ti were the strongest and most durable over time as well, but the lbs guy said that carbon trumps steel in that category. Which is why I asked this question in the first place...
Think downhill skisKerry
Sep 17, 2002 5:05 PM
CF failure modes in a vibrating system (bike frames, skis, etc.) are 1) epoxy cracking, 2) fiber breakage, and 3) fiber pullout. You don't see this when beating on a bench top with a CF frame tube. There is no question in my mind that Ti and steel are more fatigue resistant than CF.
re: Carbon vs. Titanium frame: life expectancy?the bird
Sep 17, 2002 4:09 PM
Been sorta hopeing the only threat to my carbon ride was once again,an atmospheric meltdown from the rocket like decents it alows me to make. he he ! Then again the boarshead meat truck or U.P.S. truck might put a nasty scratch in her! Maybe filling the frame up with hot water befor those winter rides to take the chill off a'int helping either! Only time will tell
Carbon damagefbg111
Sep 17, 2002 4:30 PM
Anyone ever damaged a carbon frame? The lbs guy also said that they used to have a carbon top tube that they they let customers beat on the bike rack as hard they could to see how strong the stuff is. However, he also said that Trek builds its carbon bikes in replaceable modules so that if a part of it is damaged, the owner can send it back and Trek can replace the damaged part. Since they do that, does that mean that carbon Treks are more prone to damage?
I didtao
Sep 17, 2002 5:03 PM
Had a fatigue crack on the bottom bracket shell of a '97 Trek OCLV after about 18,000 miles, only about 15mm long but all the way through to the sleeve holding the bottom bracket. Trek claims to have reinforced this area after numerous claims beginning with '99 or '00 frames, can't remember. Can't complain though, got a brand new frame/fork/headset/stem free of charge and a brand new warranty.

Carbon fiber is nearly infinitely strong but only in the exact plane of the "threads". So the trick is to figure out the best way to wind it in various directions at the points of greatest stress, e.g., the bottom bracket. So yea, a carbon top held in a vice that is wound in two directions will withstand blows from a sledgehammer. But just start to twist the vice on one side and watch it crumble to the ground.
Carbon damageTrekFurthur
Sep 18, 2002 6:43 AM
I don't think Treks are any more prone to failure than any other carbon bike out there; although it's a happy by-product of their production method, I don't think repair ease is why Trek chose this particular method of frame design.

We all know horror stories of frame failures, and we all have testimonies of frames lasting "forever." I agree with the above posters who have said that you'll get frame lust before your Giant or Trek goes blooey. Ultralight Al frames are a different ballgame altogether. Simply put, if a company only warranties a frame for one or two years, they don't have much faith in it either (this applies to bikes of any frame material).