Carbon vs Alloy Frames

Depends entirely on the design of the 2 frames.  Carbon allows builders more flexibility, especially in shaping the tubes for aero bikes.

If you are a good rider..go for carbon, it will make a difference, if like me, not at the front of the bunch, 500g is not going to make a difference, in my case I would get much more benefit by just staying out of the fridge.
A customer of mine was loading his carbon bike into his topless Mini when the bike dropped and hit the headrest...frame broke. The bike was insured however the insurance would not believe him how much a replacement frame cost. Long story.
All of the above said and done....if money was no object....would I go for carbon..YES!!

In very general terms a carbon bike will typically be a nicer riding bike. The carbon is held together with resin which acts as a dampening agent. Also the way the carbon fibers are positioned affects the stiffness and the compliance of the bike. This means a frame designer can design the bike so that it's very stiff laterally in areas while being compliant (forgiving) vertically in others, and vice-versa.

Despite the forgiving nature of carbon fiber bikes, some are very rigid and bone jarring stiff. Some frame builders will squeeze as much resin out of the bike as possible during the molding process. This makes for very lightweight carbon walls, but eliminates the dampening agent. The result is a very stiff bike that's great for climbing and accellerating, but not a very comfortable riding bike.

As previously mentioned, you can make a more aero shaped bike with carbon since you mold it to any shape you design, while with steel and aluminum you're limited by the availability of tube shapes.

The durability of carbon has improved greatly over the past few years, but not all carbon bikes are equal. Some of today's carbon frames come with lifetime guarantees, something you would never find on an aluminum and/or scandium bike.

Aluminum and aluminum/scandium bikes fatigue over time. Five to seven years of hard riding (over 5,000 miles per year) is about the limit for an aluminum or aluminum/scandium bike.

scott

agreed on both counts

And just FYI since they're so popular:

Cervelo carbon P2Cs and P3s are SUPER-stiff. Definitely not for pleasure cruising, even though folks race 'em for ironman races more than any other bike. It'll jar the heck out of you if you're on some gnarly pavement, but you'll make up for it with the rigidity on climbing and power riding.

Not really concerned what you would personally buy. I just want to know the differences. Thanks.

agreed, my p3 is prob the stiffest bike i have ever been on and will rattle your teeth out

As has been said before, Aluminum vs. Carbon totally has to do with the design of the frame. 

What I find most when watching others I ride with regularly (who have multiple bikes) if you watch the way the bike flexes as they ride, stand up to sprint, climb, etc.  Then watch the same person on a different material bike or even a different frame design and same material you can see how differently they perform.  Most carbon frames I have seen tend to be much stiffer and resist the "flex" that most aluminum frames exhibit while climbing, and sprinting, etc.  On that same note, my carbon frame (p2c) is so stiff on rough roads it litteraly shakes things loose like shifters, brakes, etc.

The major advantage from a design point of view is the ability to provide stiffness and compliance in multiple directions with composite materials (carbon), so you can build the "ultimate" bike for a specific function easier than you could with aluminum, steel, other?.  But this does not mean that the design is best for your purpose without understanding the specific benefits of the frame over another.

Michael

Just thought the Cervelo stiffness was worth mentioning, since most roadies you ask will tell you that carbon is a better shock absorber than aluminum, and should thus make for a smoother ride, but as per the posts above, it's really how you build the carbon frame - Cervelos are stiffer than most alloy frames out there. So the point about carbon's more resilient ride is really not accurate as a blanket statement. 

So it depends if you are looking for a comfortable ride or a fast ride?

Less stiff= less vibration, more comfortable
More stiff= faster, more power, more vibration and less comfortable?

So then what is the benefit of carbon bikes? From the sounds of the answers, some people think alloy is better?

No. I would guess that the people riding carbon P3's have never ridden an aluminum P3. Talk about a bone jarring ride.

My road bike is a Cervelo RS. Very stiff, very responsive, and very comfortable.

With any bike, if you want to make it more comfortable, put 25mm or 28mm tires on your bike and inflate them to the minimum PSI. Studies have shown that this is the number one factor in ride comfort.

scott

This is too general a question and statement thread.  An Aegis will ride completely different than a Scott Addict and they are both carbon bikes.  A Cannondale Optimum frame will ride completely different than a Javelin Sizzano and they are both aluminum bikes.  The biggest difference in the two materials though will be the way it fails when/if that happens.

I have both. I prefer aluminum, frankly. I just don't like the feel of carbon.

yaqui is right.  Bigger tires at lower pressure make more difference in ride comfort than frame material.  As has been said, main advantage of carbon is versatility.  It can be made super stiff or very flexy.  Depends on the design & layup.  Proposed advantage of most carbon frames is ability to dampen road 'buzz'.
There is no inherent speed difference between carbon & AL.  That lies in the design of the bike itself, and carbon allows more design flexibility.  Carbon bikes can be made a little lighter than AL, but remember that aero is more important than weight for all but steep climbs.  (visit analyticcycling.com or biketechreview.com).
Don't forget that the biggest factor in ride comfort (and optimum power output) is FIT, esp for long rides. 
FWIW- I own 3 'big name' road bikes- 2 full carbon & 1 AL roadie with reputation for stiffness (old Cannondale CAAD5).  I've ridden centuries on all 3 & honestly the difference between 'em is really pretty subtle. 

My bike built up, all components, wheels, etc is 16.5lbs. Definitely the lightest bike I own. Though I do have a heavy steel one too.

I've got Columbus Spirit. Oh did I mention that it is pink.

Edited by jeng 2009-07-30 2:50 PM