aero helmet? worth it? who wears one? (Page 2)

I would have to agree with Bryan on this...

the equation for coefficient of drag is thus:

Cd=F(drag)/(0.5*p*A*v^2)

Cd=coefficient of drag, determined by the shape of the object
p=mass density of the fluid
A= functional cross sectional area (Surface area facing the movement)
v=velocity

So by the equation, velocity is the most important as it is the squared term.  This means that anything that lowers your drag force (helmet, bottle, bike, position) will effectively lower your drag coefficient.  Also, the equation DOES show that the faster you go, the lower your drag coefficient will become (IOW the faster you go the more effect it has).
 

You make that sound like a bad thing.

Aero helmet will make you faster regardless of your speed... considering it "fits" you and you can keep that fit position held. If you've got "tailspin" syndrome (people who look down when they are exerting themselves) all you are doing is throwing up a big horn in the air.

20mph is not a magic barrier. It's not a Porsche... the spoiler doesn't deploy at a certain speed.

IMO it becomes even more apparent when you consider the power to overcome air resistance:

P = 1/2 (air density) (CdA) (v_wind)^2 (v_bike)

So for a rider in still air, the power to overcome air resistance scales with the cube of the velocity.

Shane

Aerodynamic drag increases by the square of the speed not by the cube. If you are a 15 -20 mph cyclist, aero stuff isn't going to be much of a benefit (other than psychological). As your speed increases, it gets more important.  There are trade-offs such as comfort and heat dissipation.
Total weight of the equipment is of no more consequence than extra weight around the "mid-section" however rotational "weight" or rotational inertia (of your wheels) becomes more and more important on courses where accelerations take place.  Lots of corners or hills where your speed changes alot makes the lighter wheels more important.  Bike Tech Review has rolling resistance data for a large selection of tires. There is a difference in tires. If you need to change tires, then you may as well get a set that will benefit you, especially if you keep a separate set of race wheels.

I should have been clearer in my previous post; you are correct that aero drag increases with the square of the speed, however (in still air) the power to overcome air resistance scales with the cube of the speed.

As for the 15-20mph cyclist, aero stuff is still going to be a benefit and save you time:

P = 1/2 (air density) (CdA) (v_wind)^2 (v_bike)

A change in CdA is going to result in a power savings for the 15-20mph cyclist and will likely be a larger percentage of their available power (otherwise they would be riding faster).  A faster cyclist will save a greater number of watts with a change in CdA but a slower rider should see a larger time savings for the same CdA change.

Shane

I guess people have different reasons for wearing or not wearing an aero helmet but arent aero helmets hotter than traditional helmets because they have very little ventilation?
Also, I seriously was considering buying a disk wheel two years ago and talked directly to the individual who makes HED disks in the factory and he said straight out unless someone is AVERAGING atleast 22-23 mph during a time trial or triathlon that an individual could possibly go slower than if he rode a deep dish wheel. Have you ever read an advertisement where the test wasnt done at atleast 25-30 mph?

I always look to see what the top triathletes are doing. Craig Alexander and Chrissie Wellington do not wear them at Kona! I would say don't waste your money, plus they look very try hardish. Also its great satisfaction flying past people who have all the kit and I am still on my ali bike and road helmet.

I was like you a couple of years ago and was tempted to get all the bells and whistles. Nothing substitues good training!!!

Best of luck!

how exactly does them wearing one make it a good or bad choice for someone?

And why is it always training OR aero equipment?  Who in the world doesn't think they have to train hard if they wear an aerohelmet? 

Crowie and Chrissie don't wear aero lids in Kona because they reduce cooling of the head. Kona is hot, and humans have a lot of heat in their head (it comes from the high levels of blood flow to the brain-al region). However, I don't have any cooling issues with one.

As you said, there is no substitute for good training... except equipment. But nothing at all substitutes good training AND good equipment. 

I've seen Crowie wear one elsewhere though.

And congrats for passing people.

Whoops, I think I hit a few raw nerves? If you do get one make sure all you whole set up is aero from bottle positions to your position on the bike.

Myself, I would rather use the money to get a good comfortable aero bike fit which would cut more time off your ride. Hey maybe you already have, then as long as you don't mind the look and are not stretched for cash then go for it!.

Not for me, but I am probably in the minority!



Edited by dave.wenham 2010-03-26 4:16 AM

well  my hubby just got me Tri shoes, tri bike , tri helmet....... these were my anniversary gift , at least I'll look good.lol

This article on wind tunnel testing showed similar numbers to your findings

http://www.cyclingnews.com/features/how-aero-is-aero

"The difference between the Specialized road helmet and the TT2 was 8.6W or 9.4W, depending on which set of protocols we chose."

5 watts is 5 watts. Aero helmet, wheels and other probably adds up to 20w which many people would be happy to add to their threshold power. I have neither and until I get my head position right over a long distance I won't bother.

The only raw nerve is when information presented as fact is incorrect. Aero helmets are more aerodynamic. Everything else is just personal preference, which is fine.

IMO this is key - every athlete has a limited number of watts to work with and I want as few as possible to be lost overcoming air resistance and Crr.

Shane

Before I lost my HD I had a link that showed data comparing an Aero helmet in the "optimal" head up position vs with the head down tail up and the head down was more aero, just as it was with the regular road helmet.  The key here is that moving the head down closes the hole (volume) between the handlebars and shoulders improving overall aerodynamics.  This was the principle Landis used with his praying mantis setup.

I remember that study as well, which is why the claim that if you drop your head wearing an aero helmet creates more drag is also incorrect.

At the last race I did, there was a ton of people in aero helmets.  Many were tired, had their head straight down with the "aero" portion of the helmet sticking straight up into the wind.  Maybe it's a tad mean, but it made me laugh

I agree with everything you and all the other strong athletes posted above say about aero helmets working at every speed.

Still, in terms of the OP's original question, "aero helmet? worth it?" - do you think it's really worth it for a typical BT athlete to spend $150 to save 10 seconds over an hour of racing? Especially considering what you could do with $150 not just in triathlon, but in the rest of your life?

I guess more specifically, if you were a MOP racer doing typical MOP training volume (obviously you're not - you're KQ bound AGAIN - congrats!), would you still find that aero helmet worth it?

You've got to realize that "worth it" has a very individualized definition.  That $150 means a lot less to a single 30-yo earning $126K/year (median income of a USAT member) than it does to a sole provider of a family of five earning <$50K.

Even if the benefit is the same, it's going to be more "worth it" to the person with the higher disposable income.

Edited by the bear 2010-03-26 9:16 AM

Thanks! I understand what you are saying and I would echo what Bear said above. Worth it is very subjective. What I would tell any new athlete or MOP athlete is that is it certainly not required or a "must have". Few things in the sport are beyond a bike, a wet suit maybe, and a pair of running shoes.

I'm a FOP cyclist, make good money, but even with that - for me specifically, I STILL don't think it's worth it. 

If it's for the cosmetic coolness, ok that's legit in my book go crazy. But in terms of performance, I'd personally pass. I personally would prefer to spend that $150 on other things such as race fees, underwater video camera for self-swim analysis, etc.

FOR ME:  worth it = sure it's not that expensive.  wears one = from time to time

Not as good ventilation for me but I like the sound of the air going around the helmet.  Since your ears are covered it sounds cool.  Truth is, I probably won't wear it this summer because I get hot and would rather keep as cool as possible.

As for all that other science stuff, it's been covered.  To me, in the proper position it'll make you a little faster but that is outweighed by me being a little more comfortable. 

Just get one and try it.  You won't be satisfied by internet answers until you do.  That's basically what I did.  I mathematical formula wouldn't satisfy me like practical experience would.

Gotta love the passion about a helmet though