How much faster do aerobars make you?

I was recently reading a book that talked about one of the larger benefits being the aerodynamic aspects, but they really aren't realized until about 20 or 21 mph.

I've found that below 18 mph, I can keep the same pace in or out of the aero position.  I like the aero position because I find it more comfortable over longer distances - not necessarily faster.

Yeah, well "I was recently reading" elsewhere that aerodynamics are aerodynamics, regardless of speed, and that slower riders garner more benefit simply by the fact that they're out there longer.

Horsecr@p.  Aero benefits don't 'vanish' at 18mph.

It's the position that matters (mostly).  Aerobars just generally make it easier to ride in a more aero position.  Depending on your position with/without bars, it could make a little or a lot of difference.

The standard answer people tend to give is 1-2 mph. 

Qualitatively, when I go from my brake hoods to my aerobars I have to up-shift one gear to keep from spinning out, which tells me I'm in a more efficient position, probably a combination of both aero position and bio-mechanics.  Being built like a barn door limits how aero I can get, so I think it probably more the latter.

As far as pure speed, I can sprint a lot faster on my brake hoods than I can on my aerobars.

Mark

I broke the sound barrier yesterday on my aerobars.

Honest.

You can read all about it in the book I'm writin'.

Seriously, cruising at 35km/hr in aero I lose +/-  2km/hr when sitting up.

...not sure if the sonic boom gives me any boost, though

Yeah, but that was the Canadian sound barrier. You know, the same differential that makes you guys think that chit like Celine Dion, Shania, and Rush actually sound good.

I will freely admit that having to suffer Celine could certainly result in a headache equivalent to a sonic boom, however I will simply ignore your reference to Rush and turn the other cheek, gentleman-like.

I assume you're asking about the difference between just putting aerobars on a road bike and using them, rather than the difference between a road bike and a tri bike.

I don't have any scientific data for you, but I can tell you that I have ridden the same courses both completely in aero and completely not in aero, and I usually get about a .5 - .8 mph difference for about the same effort (depending on the wind).  If you're trying to figure out if they are worth it, my vote is yes.  

My non-scientific experience...riding to/from work used to take me an average of about 33 mins. Then I put aero bars on my bike and the aero gain (I'm assuming) plus the "man, I am cool on my bike with aero bars and better haul some a$$ now to justify it before the old lady on her 3-speed overtakes me" effect has me down to about 31mins, so a 2 minute gain over 10 miles (on average). My fastest time also went from never going under 30 mins to 4X under 30 within a week of switching. Either I have gotten fitter fast or the aero bars help.

The Winchestertonfieldville PD is looking for you for breaking all those windows on Main Street!

The only time I cruise at 35 km/h is in a car.

I jumped into Hyperspace....

but as you might know "Traveling through hyperspace isn't like dusting crops, boy.".

So be carefull.