What are the disadvantages to a carbon frame?

Or, in other words, do I need a carbon bike? I never really considered carbon, but I've just seen two bikes that have me thinking. I know they're light and smooth. Are they strong, too? I have this perception of hitting a pothole and having the bike shatter. That's not really likely, is it?

Most of my riding is on the road. Some of the roads around here are kind of rough, and there's one service road that has areas of broken pavement. There's also a gate, and when it's down, we have to ride off-road on a well packed path to go around it.

The LBS near me has a used Madone for sale that I plan to test ride tomorrow. It's a few years old, triple crank, 105 components. Anything in particular I should look for?

they make airplanes out of carbon fiber…

Not sure that's relevant since an airplane, once crashed, is NOT going to be flown again ...

My frame survived my faceplant and more than one tip-over, including one that was hard enough to strip the threads on the derailleur hanger. It's been inspected more than once, basically because of its history I let a pro look at it any time I see a new paint chip, and it's fine.

If you're looking at a used frame, look very closely for any chipped paint, and especially for any linear cracks in the paint. I'd be confident buying through a LBS, simply because they've got liability problems if they sell you a cracked frame. If it makes you feel more comfortable, you might ask them if the former owner has given them permission to let you have their contact info so you could ask them about the frame's history, but I wouldn't worry if they don't.

Rough road like chip-seal or gravel is when carbon really shines.

I bought a used Ruby and can vouch for the strength of the carbon frame. I am not a lightweight and don't baby my rides. I got mild whiplash last summer when I was forced to swerve from a truck side swiping me and hit a pothole, hard. Thought the fork would snap, but it held. Now there is a gash below the head tube, but the bike shop deemed it cosmetic, no carbon damage. I will add that I usually ride it with 700x28 tires to help smooth out the ride. I will admit to being worried about the gash though, despite the shop's reassurance.

I find, for me, with the frame being stiff, the ride can be fatiguing with vibrations on long rides. Maybe my experience differs from Oakleaf because of my size, the difference in our frame geometry, or even tire pressure. I don't know. There are variables to consider. I hope your test ride gives you some answers. The tradeoff is, the Ruby is light. I do have a quality steel touring bike that is very smooth and the ride is much more comfortable. But, the bike is heavier, but not by much.

Thanks for the info. I was only kind of kidding about the pothole danger. It's just I hear that it's smooth, but stiff. My engineering brain is trying to get around that. So the vibrations get absorbed by the individual fibers?

For me, now, fit is the ultimate concern, so I have 6 bikes on my list to try out this week. Two of them just happen to be carbon, and if there turns out to be a toss-up, I'm just wondering if the carbon is worth it.

The snow has finally melted...:)

I don't worry about my carbon frame while I'm riding. I do feel I have to be overly careful with it when I'm not riding it, after spending hundreds of dollars to have a mystery crack repaired about a year after I got it. It is my first and last carbon bicycle.

I would say it is worth it. I am on my 3d carbon bike and the first 2 had various falls, minor dings, put in the back of my car with no ill effects. Do you need carbon? No. But it feels really nice. My first road bike was aluminum and that was the worst for me.
I do also have a titanium bike, which is smooth in a different way. More expensive than carbon, though.

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Originally Posted by OakLeaf

Not sure that's relevant since an airplane, once crashed, is NOT going to be flown again ...

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Oh you think so…. sure if it's catastrophic and all that's left are little pieces, but it's actually kind of scary some of the airplanes that they've refit and reflown…… There's an amazing video of a plane that lands so hard the tail falls off…. granted it was a test plane and the hard landing was kind of intentional (it ended up being harder than they really meant), but apparently the plane had a new tail fit and went on to have a long life as a test plane - eek!

So since yesterday I've ridden two carbon bikes, different brands, and I think I've found a little problem. The top tubes on both were wider than on the similar aluminum models. My inner thighs kept rubbing against the frame. Admittedly. I don't have the thinnest thighs, but they're not huge, either and I couldn't ignore it. But they were both really nice rides.

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Originally Posted by Eden

Oh you think so…. sure if it's catastrophic and all that's left are little pieces, but it's actually kind of scary some of the airplanes that they've refit and reflown…… There's an amazing video of a plane that lands so hard the tail falls off…. granted it was a test plane and the hard landing was kind of intentional (it ended up being harder than they really meant), but apparently the plane had a new tail fit and went on to have a long life as a test plane - eek!

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F1 cars are carbon fiber, and I'm pretty sure the chassis (what is the plural of that word?) are repaired when needed. The thinner parts like wings tend to shatter into shards so they get replaced. The safety standards for the cars are strict (and amazingly effective) so repaired carbon would not be allowed if it didn't meet the structural requirements.

However I don't think my mass-produced bike is as high a quality material as an F1 car.

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Originally Posted by Muirenn

When aircraft crash and the carbon-fiber burns... I would hope that is not relevant to bicycles.

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lol.. only in the movies (thinking of the myth busters episode that showed how really hard it is to crash a car and have it catch fire or even more crazy, explode- but how it seems *every* crash in the movies results in an eye catching, but completely fallacious fireball) :rolleyes:

I'd make a guess the carbon fiber on an F1 car isn't structural, but just an aerodynamic shell, so I can't imagine repairing it wouldn't be a safety issue, unless the repair could possible shatter or tear off under the pressure of the wind? I have seen carbon fiber bike frames fail - but as far as I know all the failures have happened during or after a crash which damaged the carbon. For sure care needs to be taken, as damage done may not be readily visible, but I wouldn't expect normal knocks to have any affect - there are carbon mt. bikes, so a pothole shouldn't pose a problem. I've also seen aluminum, ti and steel all fail too, nothing is invulnerable.

Potentially slightly more relevant to this discussion is Ducati's failed experiment with a carbon fiber frame. The bike was famously too stiff and wouldn't steer. They've gone back to aluminum for 2015, but are keeping the carbon fiber swingarm.

The carbon is also structural in the cars. They can get away with it because of the much, much, much larger tire contact patches.

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Originally Posted by Muirenn

You mean that tires contact the road in a much greater surface area than a bicycle tire?

Actually,...English, please? :D

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There's a good picture of the cars here.

http://www.formula1.com/content/fom-...ed-podium.html

I think there must be something more solid in the part above/behind the driver's heads, which is there for safety reasons. I've seen the driver walk away unhurt after his car flipped upside down and then bounce rightside up again. Whatever is in there, the car did not break apart from the impacts.

Anyway, as I said before, they have different requirements and budgets in mind when they make the carbon for these cars vs. mass-produced bike frames. I can't find the link to it, but I recall BikesnobNYC writing about his carbon road bike cracking pretty easily, from hitting against a lamppost or something similar.

I stand corrected - I was looking at an old F1 car frame that was aluminum. It does appear that current cars have a carbon monocoque chassis/cockpit. They are specially coated so that they will not splinter in case of an impact, something which obviously bikes don't have, but I would guess flying carbon bits aren't going to be a huge problem in bike crashes either.

I don't know about bike snobs bike… that sounds unusual of not improbably, but the carbon part I have seen break without provocation was carbon spoke wheels.. which had a bad habit of simply shredding themselves

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Originally Posted by Muirenn

You mean that tires contact the road in a much greater surface area than a bicycle tire?

Actually,...English, please? :D

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Yep. :D A car has so much more grip (than bici or moto), and it doesn't steer by leaning, so having a certain amount of controlled frame flex isn't critical to handling in a car the way it is with a two-wheeled vehicle.

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Originally Posted by IBrakeforPastry

So since yesterday I've ridden two carbon bikes, different brands, and I think I've found a little problem. The top tubes on both were wider than on the similar aluminum models. My inner thighs kept rubbing against the frame. Admittedly. I don't have the thinnest thighs, but they're not huge, either and I couldn't ignore it. But they were both really nice rides.

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I get this, sometimes...I have big thighs and relatively narrow hips (no thigh-gap for this girl -- I could be emaciated and my thighs would still touch. Even as a scrawny teenager my jeans always wore our first in the inner thigh area). Is it possible your knees are diving inwards too much while you pedal, too?

I will echo others who recommend carbon. I rode some godawful potholed roads on my Cannondale SuperSix and even was involved in a paceline crash when the rider in front of me had some debris tangle in her rear wheel and drivetrain and took us both down. My frame is still flawless and strong. SUPER smooth on our rough chipsealed roads here in MI, too.

My knees do point slightly towards each other. I could never be a yoga model because I'm just not linear. Knees point in, calves bend out. Even when the knee joint is fully straightened, my legs don't look straight. It doesn't cause any knee problems when pedaling, it's just the way I am. I can consciously pull my knees out, but it takes mental energy as well as physical energy, and isn't natural.

Anyway, I ended up getting a good deal on a Specialized Vita from last year. My neck is much happier with upright bars. I will keep a basic drop bar bike for those few times I might want to do something different (or ride with a friend). I'm sure that the Vita will serve me well, just like my Sirrus did, before it was stolen.

Thanks for the interesting discussion. Besides the Wright Brothers owning a bike shop, it's fun to see how all this is connected. And I've worked in aviation for 25 years :)

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Originally Posted by IBrakeforPastry

So since yesterday I've ridden two carbon bikes, different brands, and I think I've found a little problem. The top tubes on both were wider than on the similar aluminum models. My inner thighs kept rubbing against the frame. Admittedly. I don't have the thinnest thighs, but they're not huge, either and I couldn't ignore it. But they were both really nice rides.

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Another thought, if you end up not getting a carbon frame due to that... Get a set of nice wheels! I have Topolino wheels with kevlar/carbon spokes on an aluminum frame - that's a nice ride too!