johngwheeler

asgelle

I'm not sure how you can compare a purely objective measure such as reduced CdA with a subjective measures such as comfort or fun. Not to mention a bike that is twitchy and impossible to control for one rider can be responsive and a dream to ride for another.

It sounds like you're coming to this with your mind made up and are just looking for confirmation.

Dean V

No.

johngwheeler

Lazyass

My DB is "wind tunnel tested". Very sweet frame, but realistically I'm about as fast on my 34 year old steel bike with downtube friction shifters and a 6 speed freewheel.

chainwhip

johngwheeler-

No expert on the subject here. ..and I don't own an aero bike.

That said, you'll find general agreement that
most aero gains can be had from improvements to your position on the bike.

Your body's profile will always create a larger "wind shadow" than your bicycle's frame and fittings.

asgelle

But that's hardly relevant to the discussion here. No matter how perfect your aero position is; in the end, if you're going to ride a bike, you need a bike to ride.

chainwhip

​​​​​​​asgelle-
This *is* BF, so I guess random, contentious comments that don't add much to the conversation are pretty standard.

Lazyass

I recall reading that bikes are tested at speeds of 30-40 mph, slower than that probably doesn't make much of a difference. If you live in the mountains and do a lot of high speed descents or you're in the pro peloton pushing an inhumanly fast pace I'm sure it would be a more noticeable advantage. I will say strong headwinds feel slightly less painful but that could be in my head.

asgelle

Bikes are often, but not always, tested at 30 mph.; but that's to get good quality data, not because it's a magic speed where differences appear. Since drag scales with speed, it doesn't matter at what speed the tests are done. The results are easily interpreted for any speed desired.

Maelochs

Okay, I will take a shot.

From what I hear ... most aero frames tend to be Very stiff. They are designed to have a low cross-section, not to be strong and compliant to absorb bumps and rattles.

Second, from what i hear, as aero resistance increase as the square of the speed or some such, it ramps up quickly at high speeds ... and is not that big a deal unless you are cruising at about a steady 18 mph. The way i understand it is a few percent less drag at 15 mph is almost impossible to measure ... adn 17, impossible to notice ... at 18 mph, measurable, and by 20 mph fighting the wind is all that matters. The increase in power needed to get from 15 to 16 is not enormous, while the increase needed to go from 20-23 is almost a two-thirds increase or some such. i could look all this up .... so could you. I tend to ignore the numbers after I have read them and retain the conclusion---which in this case was that until I was steadily cruising at over 18 mph, minor aero improvement were pointless.

Finally, as @chainwhip notes---if you want to be more aero, ride more aero. An expensive aero frame might get you a few percent savings, but it's not like most bicycles have huge frontal area .... and the fat parts, like the head tube, are pretty much fixed. Tube shape can gain ridiculously tiny improvements ... and putting a bottle in the rack can waste them all.

The real are to impact aero is rider position ... where everything else (except a disc wheel, because of turbulence form spokes) will provide the very smallest improvement, getting your head down with elbows in saves a World Tour rider 10-15 watts. of course, not everyone can efficiently deliver power in that position, and pretty much no one can hold it for more than some minutes ... and it is useless for climbing. But while you are in that ducked down, laid out, tucked in position, you are cutting a lot of frontal area.

if you have wrung every watt of power out of your body and still need more speed, duck your head and pull your elbows in.

But for the "average non-competitive cyclist"? Buy a bike that looks good. The eighteenth of a watt your non-compliant down tube saves you will be lost to the fatigue caused by the extra vibration.

But you are not average---really, no one is. So ask yourself----are you always either in the drops on on the hoods with your arms and back parallel to the ground and your head all the way down so it is entirely masked by the wind-shadow of your body? if that is how you ride, you might gain a tiny but likely unnoticeable improvement by buying an aero frame. if you tend to ride on the hoods with your body at any other angle than parallel to the ground ... keep smiling and riding and forget that stuff.

rubiksoval

The slower you are, the more absolute time you'll save by being more aero.

So yeah, there's an advantage.

Whether that advantage is significant to you, or worth the money...that's another question.

HTupolev

Many people complained about early aero bikes, because the aero tube shaping made the paths from the wheel axles to the contact points very vertically stiff. That's why a lot of the current stuff has a lot of design choices to increase compliance, like short seat tubes or suspension mechanisms like IsoSpeed.

What's "significant" to you?

Obviously it depends on the particular setups being compared, but from what I've seen, current aero frame versus non-aero frame would be on the rough scale of a couple watts at the speeds we're talking about.

rubiksoval

You realize that in both those situations, an aero bike will be faster?

Why does this stuff always turn into an either/or situation?

It never needs to be.

asgelle

I don't think you appreciate all the factors that determine fluid drag. There's much more to it than frontal area.
You're off by about two orders of magnitude.
Don't you realize that the benefit from aero equipment on the bike is the same regardless of rider position?

Lazyass

Wind drag increases with speed.

wphamilton

I always thought that aero frames tended to have greater cross section, but the shape with a lower coefficient of drag more than makes up for the greater area. That's why they're more rigid, in the same way that wider tubes with thinner walls are more rigid.

Yes of course there is a real advantage for the "average rider", if by that we really mean "lower speeds". The effects of drag don't just cut off at some particular speed.

chainwhip

You might consider that while that's arguably factual, except as a style issue, it simply doesn't matter for 85%+ of the demographic of road riders.

kbarch

The first couple of carbon bikes I had (including my first bike as an adult) were both aero frames. Although for a while now I have had a non-aero bike I take on long rides, it's steel, so that's what I chalked up most of the difference to, in terms of ride feel. As you might imagine, it was only at high speeds when all the aero advantages were appreciated. Generally, however, I didn't notice much difference in ride feel - that is, enough to make me wish I'd taken the other bike - until about 60-70 miles. Now, however, I have a carbon bike with a more conventional frame for comparison. I think I can enjoy it a bit longer than I could the aero bikes (I no longer have one), but still not as nice as the steel bike.

asgelle

Thanks for pointing that out. What do you think I meany by "scales"?

Lazyass

If you comprehend what I wrote you'll realize I basically said an aero frame isn't much of an advantage with the average rider going a slower speed. I don't really care about the whats or whys of wind tunnel testing speeds, that was an aside. I care about what I feel when I'm riding. I do know jet aircraft aren't wind tunnel tested at 30 mph.

Maelochs

This thread is destined to go the way of weight threads .... saving even a nanogram will make it easier to pedal, so every nanogram saved is important ... versus ... most people cannot even feel the difference of a few grams, and on the flat, weight means very little ... versus "micro-accelerations will sap a riders energy even on the flat," versus "a few ounces of weight either way for an average rider ... '

then there is the "Don't lose weight on the bike, lose weight on the rider" debate. then there is the 'A couple water bottle are more weight (or in this case, more drag) than is saved by all that expensive technology."

And in every case, anytime someone does not 110% agree with someone else, it is taken a a personal affront of the highest severity. respect for differing viewpoints is never to be found anywhere.

Nobody really wants to come to a wide-ranging series of generally helpful but not rigidly prescriptive series of ideas by which all this could be explained to a novice seeking the input of experienced riders ... so every few weeks we repost the same lame, off-the-point, unhelpful arguments over and over again.

Have a ball, folks..

asgelle

As rubiksoval pointed out, slower riders save more time through aero equipment.

Maelochs

By the way ... I have never forgotten about "Lazyass' theory of preride bathroom weight reduction",and I never go for a ride ride without gain the benefit of that wisdom.

Somebody should have explained that theory to Tom Dumoulin before that Giro stage last year.

HTupolev

Only in absolute terms for a similar course. Relative performance impacts of aero are smaller for slower riders.