I understand that it all comes down to the engine on the bike. With that said would a carbon bike help with speed?
Here is what i know, or at least what I think i know. Aluminum is cheaper and a harder, stiffer ride. Carbon is more expensive, better bling factor and more comfy. Would you expect the same engine to push a similiar carbon frame faster than an aluminum frame?
no
.
Ok, you bring up two different questions/points. For one, a bike will not go faster or slower based on material. Secondly, your summarization of carbon and alumium bikes aren’t always accurate. Aluminum bikes can be comfortable. Carbon bikes can be stiff if they are designed that way.
Again, you bring up two separate issues. Are you asking about the “speed” of a bike based on frame material or are you asking about ride quality?
why not demo a bike that has both materials in the model and see if for you it is different?
I am still pretty new at all this, but the difference between my aluminum road bike and carbon fiber tri bike is unbelievable - I am really noticing how much faster/easier climbs are for me on the carbon fiber. I can accelerate it MUCH easier.
For me that translates to wanting to go demo carbon fiber road bike frames…
Though you point out that they are two completley different bikes, so they would ride way different. My dad has a Scantte(sp?) bike from Performance, I rode it, then test rode an SLC, the difference was insane. My old Trek 2000 frame is better then the performance one.
No. I currently have two carbon bikes. A Giant and an Aegis. The Giant is very smooth riding, the Aegis is very stiff. Both carbon, both very different in design. The Aegis feels much stiffer than an old Cannondale caad3 I used to ride. I used to ride a Klein (aluminum)many years ago. I believe it was probably the fastest bike I have ever owned. Alas, it cracked. Anyway, so no. Just because its carbon, doesnt necessarily make any faster.
It depends what the bike is being used for. I found for cyclo cross, carbon does go faster than aluminum. On the rough stuff carbon floats over the bumps the the aluminum sends the hit straight back at you slowing you down.
I understand that it all comes down to the engine on the bike. With that said would a carbon bike help with speed?
Here is what i know, or at least what I think i know. Aluminum is cheaper and a harder, stiffer ride. Carbon is more expensive, better bling factor and more comfy. Would you expect the same engine to push a similiar carbon frame faster than an aluminum frame?
Bicycle designer’s creedo:
“It’s not so much the material…it’s what you *do *with it that counts” 
For example, there are very FEW carbon fiber road bikes for which I’d trade my aluminum Soloist frame. I really think you are making some unwarranted, broad generalizations above.
Well, Cervelo claims that their P2C and P3C are faster than the old aluminium P2K and P3, but either of these aluminium bikes are still faster in the wind tunnel than most carbon bikes on the market.
Aerodynamic design makes a frame faster, not the material by itself.
why not demo a bike that has both materials in the model and see if for you it is different?
If you do that, you better make sure all other pieces of equipment (wheels, tires, saddle, seat post, handlebars, hoods, etc, etc) are identical and the tires have the exact PSI. Use the same fork too, and hopefully both bikes have the same geometry.
Same shorts too. Chamois thickness could lead you to believe that one bike rode rougher than the other
Carbon isn’t necessarily faster than Alu but it does have several advantages over Alu which would lend it to being “faster”.
Since carbon is a fabric it can be moulded into any shape the designer wants thus lending it to being more aero. Alu bikes are usually made from extruded pipes that are then cut and welded together limiting the aeroness of the build.Again because carbon is a fabric and formed in a mould it can be layed up in varying thicknesses to impart different properties. Areas under high load can be made thicker and areas under less load can be made thinner thus optimizing strength and weight. Alu is more difficult to manufacture with varying thicknesses and thus is a series of compromises concerning weight and strength.Because CF is a fabric the weave of the fabric can be varied to impart different properties and to impart strength in one direction and suppleness in another depending on the fibre orientation. Alu is a metal and it’s strength is uniform throughout (it’s strength is determined more by thickness and shape than consistency).
so when you demo frames aren’t you supposed to just essentially keep it one gear and see how you accelerate??? are you telling me that before you buy a bike you have to try it with exactly the same components etc? same shorts? that flies in the face of demoing!
pretty consistent for me to see a difference in my bikes, and I am no expert!
are you telling me that before you buy a bike you have to try it with exactly the same components etc? same shorts? that flies in the face of demoing!
We’re talking about removing as much “subjectability” as possible. An aluminum bike with under pressure tires and a fat saddle will probably feel nicer than a carbon bike with maxed out PSI and an SLR saddle.
are you telling me that before you buy a bike you have to try it with exactly the same components etc? same shorts? that flies in the face of demoing!
We’re talking about removing as much “subjectability” as possible. An aluminum bike with under pressure tires and a fat saddle will probably feel nicer than a carbon bike with maxed out PSI and an SLR saddle.
oh come on, no shop is going to send someone out with underinflated tires, and as to seat, well you could stand and climb but most high end bikes don’t usually have fat saddles to start with.
now you are just hair splitting
I have had a Giant carbon road bike for the last few years and I love the ride and stiffness. When it came time to purchase a Tri bike, I just couldn’t quite afford the carbon frame bikes that I wanted so I ended up with a Guru TriLite. Alu front ended mated to a carbon rear end. I was REALLY concerned about the ride of Alu compared to my carbon Giant. Turns out that I can’t tell the difference. As far as “faster” goes, I agree with other posters that it has more to do with the aerodynamics of the bike. But as far as comfort goes, I subscribe to the “it depends on what you do with the material” school of thought. The old adage that Alu is stiffer and carbon is more comfy just doesn’t seem to hold true anymore AS LONG AS the frame maker knows what they’re doing. My experience so far is that Guru knows what they’re doing.
So IMHO (assuming all other components were the same) as long as both bikes were had similar aerodynamic qualities and as long as the frame manufacturer really knew what they were doing with the materials, I think the same engine would be about the same on each bike.
I think, given the shapes you can form carbon into, you can make a bike faster aerodynmically, but from a materials standpoint, I think fast depends on the rider…
Bob
are you telling me that before you buy a bike you have to try it with exactly the same components etc? same shorts? that flies in the face of demoing!
We’re talking about removing as much “subjectability” as possible. An aluminum bike with under pressure tires and a fat saddle will probably feel nicer than a carbon bike with maxed out PSI and an SLR saddle.
oh come on, no shop is going to send someone out with underinflated tires, and as to seat, well you could stand and climb but most high end bikes don’t usually have fat saddles to start with.
now you are just hair splitting
I am only discussing the original topic. 15 psi will make a heck of a difference making you think one way or another about the subjective “feel” of a bike.
Yes, Carbon helps with speed.
… in draining your bank account.
are you telling me that before you buy a bike you have to try it with exactly the same components etc? same shorts? that flies in the face of demoing!
We’re talking about removing as much “subjectability” as possible. An aluminum bike with under pressure tires and a fat saddle will probably feel nicer than a carbon bike with maxed out PSI and an SLR saddle.
oh come on, no shop is going to send someone out with underinflated tires, and as to seat, well you could stand and climb but most high end bikes don’t usually have fat saddles to start with.
now you are just hair splitting
I am only discussing the original topic. 15 psi will make a heck of a difference making you think one way or another about the subjective “feel” of a bike.
However, even when using the exact same wheels and tires, your subjective “feel” of a bike may not tell you which is faster.
For example, when I tested my P2K vs. the borrowed P3C, the P2K “felt” faster to me (I wish it was too). But, the power meter and speedometer didn’t lie 
“a similiar carbon frame faster than an aluminum frame”
There’s your first problem…there is no such thing as similar carbon and aluminum frames. Tube shapes, sizes, welds, layups, etc. These things vary sufficiently between any carbon and aluminum frame as to make this an impossible question.