wphamilton

Apparently they are designed for both scenarios.

Laminar air flow tests are very useful for low speed air flows. This is an important point, one which I believe another poster has overlooked when he opined that only the frontal area should matter for aerodynamics.

Well they are comparable I think, although at extremely high Reynolds numbers (high speed) flows are more turbulent.

I think that you're postulating a ubiquitous turbulent condition at ground level along the roads. I'd agree that wind tunnels do not simulate that kind of environment - but IS there really such a phenomenon? I'd expect something like the normal pressure gradient and associated flows resulting from surface adhesion.

RollCNY

It is a big deal if you want it to be, and it isn't if you don't. Just like carbon deep profile wheels, and DuraAce versus Tiagra. If it gets your to ride, it's a big deal. Enjoy.

delcrossv

Essentially no part of a regular bicycle exhibits laminar flow. World record streamliners, which are CFD optimized to within an inch of their life, exhibit laminar flow over significantly less than 50% of their body length. It's a safe assumption to make that you have fully developed turbulent flow with a regular bike (aero tubes or not)

wphamilton

That may in fact be true, but I've not seen that demonstrated. My understanding is that you generally DO have laminar flow at some point on most of the curved shapes, but separation at various points. Do you have a source you can point me to, that there is no laminar flow on any part of a bicycle?

There are also other effects that influence drag on shapes behind the leading edge. Are you seriously telling me that only the frontal cross section makes any difference on a bicycle frame?

delcrossv

Note : "essentially" For example,the leading edge of the front wheel may, at narrow yaw angles, exhibit laminar flow for some part of the section, but it's pretty short. Absent a fairing, a bike+rider is not NACA foil nor even an approximation of one. That said, improvements in Cd can be had without invoking laminar flow.(E.g. skinsuits etc.)

Not at all, but in most situations the "A" in CdA is the largest contributor (and the easiest to address). E.g: riding straight armed on the tops vs a full crouch on the drops. (That changes Cd as well). Compared to the rider, the frame is a pretty small contribution.

wphamilton

I'm not going to argue (much ) since I originally said essentially the same things. That the tube shapes are too short to be foils and the top tube mostly doesn't matter, and that the gains from aero frames are near to trivial for most purposes.

And yet, there are some measured gains. As I mentioned - speculated - there is/can be improvement at the head tube and transitions between surfaces. Behind the head tube, seat tube/post, behind the seat tube, at the bottom bracket. I'm fairly confident that improvements there are at least partly due to laminar flow on those surfaces. I suspect that the shape of the other tubes don't have much to do with it.

delcrossv

I think we're getting to the same place from two different starting points. You are probably getting better flow with a streamlined tube but it could be either from a reduced frontal "A" or a better Cd or both. Even if the flow trips early on, you'll get less suction by having a streamlined tube.(Better Cd). I think the table with relative gains/$ is probably pretty spot on- an aero frame is pretty low on the list.

Mr IGH

I ride with a club that has many riders on fancy aero frames made of carbon fiber. Half of those fancy aero/CF bikes have 32 round spoke wheels. It amazes me how misplaced their money is. An 18lbs aero framed bike with 32 round spoke wheels is slower than a 24lbs steel frame with a set of Mavic Askims (20 aero spokes) under any conditions.

caloso

Have you considered that those may be their training wheels and that they save their lighter, more aero wheels for race day?

Commuting/training.



Racing.

mike12

I haven't read this entire thread, but do have a question. Would the aero frame matter as much in a paceline vs being at the front of the line or riding solo? I'm assuming the benefit would be diminished if in a pack, but you know how assumptions work sometimes.

delcrossv

Aerodynamic aids generally will matter less in a pack than solo. See the chart a few pages back for relevant CdA's. You'd be able to pull a little longer with an aero bike so in that case it may make a difference if you were in front.

delcrossv

Or you can insert "more expensive". Truth be told, Aero trumps weight down to very slow speeds/ very steep grades. Heavier aero wheels will give more gains than lighter less aero wheels over most courses.

See:

Wheel Performance

or more recently:

Flo Cycling Blog: FLO Cycling - The Great Debate - Aero vs. Weight *Edited

RR3

Yes......$5400 worth of matter.

Parlee Cycles - ESX Aero Data

caloso

My race wheels are both lighter and more aero than my training wheels, but the biggest price difference between the sets are the tires (tubulars v. clinchers).