When companies market their aero gear, they make claims like, "60 seconds faster over 40km going 25mph when compared to non-aero gear," or something to that effect.

Using this example, my question is, if you wear the aero gear and go slower than 25mph, will you save more or less than 60 seconds? Intuitively, most people would say that the faster you go, the more aero savings you'll have. So if you go slower than 25mph, you'll save less than 60 seconds. But I've also read the opposite.

Does anyone ACTUALLY KNOW the answer. Gut feelings or guesses aren't going to help here. Thanks so much!

Okay... I don't know if you forgot to mention power savings or increased speed per watt but -
If you travel at 25mph with *any* equipment, you're going to have the same time taken over 40km...

But in regards to power, the higher the speed (and therefore power), more aerodynamic equipment will provide increased savings of power at a higher speed.

Unless the route is hilly, aero stuff is more efficient than light equipment (unless it's full of traffic lights).

Thanks for the response. I think my original post wasn't so clear so I've edited it. My question is, if you wear aero gear, but go slower than the speed at which the company says there are x number of seconds saved when compared to non-aero gear, will your number of seconds saved go up or down. Hopefully that makes sense now.

O, I am not prepared to research the correct answer to your question. But amount of time saved isn't really important. I can tell you that you will always arrive at the finish line earlier with the aero gear. Less earlier when travelling at lower speed, but always earlier.

Here's one possible answer. The guys at Flo Cycling say that the slower you go, the more time you save, which is counter-intuitive. So if a piece of aero equipment saves 60 seconds over 40km going at 25mph when compared to not using that aero equipment, if you travel slower, let's say at 20mph, you'll actually save more than 60 seconds.

https://flocycling.blogspot.com/2012/...odynamics.html

I think that is only up to a point. At some point (slow) the aero effect becomes so minor that you actually save less time. It is not a monotonic relationship.

This has been extensively studied and the results are well known in triathlon circles, particular at Slowtwitch.com.

THe answer:

- YOu save a greater % of racetime the faster you go. So, a 30mph TT rider will save a greater % of time in a TT than a 15mph rider.

- However, because the slower rider is on the course for a longer period of time, the total amount of time same (actual minutes, not % of total race minutes) is usually very close to equal of that of the rider at 40k. At 112 miles (ironman distance), the total time saved by the slower rider is usually more than that of a speedy rider, despite still having a smaller % of overall race time saved, in the order of minutes.

Do note, however, that unless you really care about finishing the ride slightly earlier, the aero gear won't matter to you. For tris or time trials, yes. For a training or group ride? You won't notice.

Op, just go to an online power calculator like Kreuzotter and play around for yourself. See the speed differences of different aero profiles for someone with 350 watt FTP, and figure out a base time and best time for 40k. Then do the same thing for someone with an FTP of 150 watts, same aero profile for base and best.

Then you can see for yourself.

Slowtwitch seems like an impressive site, but I'd like to see links to both "studies" and analysis. There is no doubt a good deal going on when aero-oriented improvements are introduced and I'll plead guilty to not having spent much time on this, but I believe a first order aero model shows that the percentage saved will be constant. The faster rider saves 1.7% which at 25mph is 60 seconds. The slower rider saves 1.7% which at 20mph is 75 seconds. There are certainly other factors which affect this relationship.

You don't need "studies" for this sort of relatively simple analysis.
One can quite easily model what is going on and all kinds of online calculators can easily give you the answers, as mentioned before in this thread.
Being earo will always make you faster, at any speed.
The faster you go, the bigger the relative difference will be.

...

That's the problem. It's NOT a constant.

As a PERCENT OF OVERALL TIME a faster rider has a greater saving and that's all that matters. Talking about the TOTAL amount of time saved is a false metric that creates the marketing non-sense that prevails in the land of 20deg yaw angles.

From a racing POV, I think you are totally correct. However, beyond competitive racers, I think there are a number of people out there who would find total time saved a valid metric, for their purposes.

I am thinking of the time trials I have done, usually there are a number of people who are not remotely competitive, but are out there to get a personal best. Good on them for being out there (as opposed to the couch), and for them, being able to spend money and reduce the total time they spend on the course is probably worth it.

^^^ I understand your point and agree that pretty much anyone will benefit from aero gear but the question was about who benefits more. The answer to THAT question is faster riders.

You're absolutely right about the simple analysis. Let's assume these aero improvements correspond to a percentage change in drag coefficient. Velocity is Power divided by Force. The aerodynamic force will change linearly with drag coefficient. So for the 25 mph rider at constant power his time will be proportional to drag coefficient. Similarly for the 20 mph rider, but the 20 mph rider is going slower hence the time saved, a fixed percentage, will be greater.

This may be counter-intuitive, but it's the result of that first order analysis we're talking about.

A slow rider of course isn't going to wear a skin suit for its very small percentage improvement, but would benefit greatly from an improved position.

I haven't found an online calculator that will let the user vary drag coefficient directly, but the better ones permit entering rider position which should yield a similar result.

^^^ It's not a fixed percentage. It's not linear. The faster you go the greater the benefit. Even the marketing copy shows this.

If TOTAL time saved was the goal and aero benefits were linear and fixed then going 10km/h vs 40kph would mean that the slower rider saved more "time".

Since the real question is who benefits more then the real answer is a faster rider because aero effects become more pronounced at greater speeds.

Claiming a slower rider saves more time is just statistical manipulation. It flies in the face of common sense.

From Kruezotter: kept all rider weight and height, bike weight, elevation, grade, and wind constant.

Variables used: Riding in drops: Cd*A=3.6567, riding tri-bike: Cd*A=3.0304

At a constant 350 watt output, rider travels at 25.7 mph in drops, and does a 40km TT in 58 min. Same output, rider travels at 27.3 mph on tri-bike, and does a 40km TT in 54.6 min. Speed increased 1.6 mph (6.22%), and rider saved 3.4 min.

At a constant 150 watt output, rider travels at 18.9 mph in drops, and does a 40km TT in 1 hr 18.9 min. Same output, rider travels at 19.9 mph on tri-bike, and does a 40km TT in 1hr 14.9 min. Speed increased 1 mph (5.29%), and rider saved 4 min.

Perfect.

Take that to a previously mentioned forum where it is 'well know' that slower riders benefit more from aero equipment because they spend more time on the course.

/thread.

No no. That only proved that the Kruezotter model is faulty and can't be trusted. On with the thread.

Sorry. I forgot we hadn't gone through denial, yet.

Once we have and we also cover obfuscation, the summoning of an 'expert', the steadfast refusal to accept facts and 3 or 4 more pages of bickering and name calling then can we end the thread?

I do think the model is flawed in its assessment of different rider positions (IIRC, it has a mountain bike as more aero than a rider on tops of bars), but from a straight math tool, seems like it proves a simple point simply enough.

The scientific method at it's best.

fify.

This thread? This is why we can't have nice things.