Aero road bikes vs non aero road bikes

well there ya go, the aero ones cost more. 

if you plan on having 1 bike for both road and tri, it's not a bad way to go. or just get a std road bike and add a tri bike later.

Aero road bikes are significantly faster (look a what a brick the downtube of a regular bike like a Madone is).  They will save you 10-20W at FOP Time Trial outputs.

VeloNews covered it a bit here: http://forums.competitor.com/topic/11390

Lava also ran a test (can't find it online) showing the best aero road frames tested well against all but the best tri bike frames.

Some folks have built up S5s for tri-duty:

I have a Connondale 6/13 carbon that I recentley dropped the bars, flipped the stem and added aero bars.  I can tell you that my average mph over my 25 mile training route went up 2 mph.

It took several rides to dial in the seat position and I purchased an aero bottle that fits between the aero bars so you don't have to come out of the aero position to hydrate. 

My bike is no longer what I would consider to be comfortable though.  I don't have any pain or anything like that but riding in the aero position is not really for a stroll through the park.

I just finished a OLY tri yesterday and my average mph over 25 miles was 22.9 mph.  For me that is a good average and it is a direct result of training and racing in the aero position.

Your P2K will be more than adequate.  It is a fine solid bike.

there is a fair bit of data out there which can be used to confirm that aero road frames are indeed faster and by how much, some of it can even be trusted as manufactuers are in the habit of testing each others products as well as their own!

i was involved in writing a little analtical tool which allows you to run comparisons on some of the frames linked to such data, try the link in my signature if interested.

I think we can conclude that Aero frames test much faster in the wind tunnel than non aero frames.  However, their performance in a road race, that include much more variability than a wind tunnel, cannot be easily quantified...especially when different riders use different tactics.  Current wind tunnel tests simulate what a bike/rider experiences when out in front (like a TT or tri).  Maybe they should also do wind tunnel tests where there are 2-20 bikes/riders in front of or to the side of the bike/rider they are actually trying to test to see what actual differences you can expect from an aero road frame when used for road racing.

If you are looking for a road bike to also use in triathlons or time trials, then I would absolutely recommend an aero road bike frame.  For road racing purposes...hmm...I would think their aero performance would at least negate their weight disadvantage, but how much more than that is anyone's guess.

I think the advantage in a road race would only be if you expected to be off the front in a break. I don't think I'd want one in other scenario's, even a sprint.

Aero road bikes are used heavily by sprinters.  Pretty much every top sprinter uses one: Cav's Venge, Greipel's FAST, etc.....the exception is Sagan, who's sponsor doen't make an aero road bike yet.  In a TdF sprint, you're not really accelerating that much.  It's going from 65kph on someone's wheel and accelerating to 70kph in the wind.  At those speeds aero is key.

They also work well for domestiques who need to be at the front pulling (or chasing back after grabbing bottles).

Given the UCI's weight limits, there's really no downside to having an aero bike, since you can build it to right at the maximum allowed weight.

Even for us who don't race in TdF-level pelotons of have UCI restrictions, aero bike make a lot of sense for pack racing (just like deep-V wheels do).

Questions...because I actually don't know...

Does frame aerodynamics change significantly when you're sprinting swaying your bike violently left and right?

Does the aero frame tubing impact stiffness, and if so, how much stiffness, and is it enough to sway a sprinter to use a non aero frame for improved stiffness?

Tour bikes, even aero framed tour bikes can get way below the UCI limit.  I've seen the SuperSix Evo get as light as 11 pounds.  If aerodynamics are so important in a sprint, why not use an 808/1080 combination to get maximum benefit?  Or is this a stiffness question again?

Again...none of these issues are related to using an aero framed road bike for tris or TTs.

Swaying the bike causes some vortex shedding and will impact aerodynamics.  We don't really know measurable specifics since wind tunnel setups have the bikes in a fixed position.  Also sprinting is very hard to do repeatably. 

Ounce-for-ounce, aero shaped tubing is not as stiff, so designers use more carbon to compensate (that's why tri bi frames weigh more than road frames).  

The reason sprinters don't use 808/1080 combos is that they need to ride for 100mi. in a closely bunched pack where bike handling/stability matters.  Most pros use 50-60mm wheels, which are almost as aero (especially the new "firecrest" type profiles), but handle easier in crosswinds.  Cav used to use a 404/808 combo (I think he uses dual 404s now).

just got a S5, it is really fast in the wind tunnel, for me this is good enough for both tri and road..

http://www.cervelo.com/en/bikes/s-series.html