Is there any disadvantage (aerodynamic or otherwise) of having aerobars tilted downwards. I’m trying it with my T2 Cobras and its kind of nice.
Nothing that can be measured without a windtunnel (good for some people and positions, bad for others). If you like them like that then ride them like that.
It’s been mentioned here a few times that a slight tilt upwards is a bit more aerodynamic but you would need to go to a tunnel to check it out.
By tilting the extensions down you may be raising your elbows and thereby raising youself higher on the front end which may feel more comfortable.
Take a picture from the side and note your elbow position with the extensions pointed down like you have them. Then take another picture with the extensions flat. Compare the pictures, you might noticed you are lower in the second picture.
jaretj
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Nothing that can be measured without a windtunnel
Or a powermeter, the right locale, a bit of time, and some rudimentary math skills.
I experimented with my forearm angle two summers ago, and found an upward tilt comparable to that of my old non-adjustable Hooker bars increased my CdA significantly. The same was true on the day that my bars slipped a little below level as I was warming up. The sweet spot turned out to be exactly where John Cobb’s rule-of-thumb said it would be.
I tilt mine down slighty (see pics above…only slightly more). I feel this is much more comfortable, aero, and allows me to pull up more when hammering or climbing.
It works for me. But, my new Aero Concepts integrated bar does not tilt, so I have to either raise the pads or replace the s bends, which raise my hands, with straight extensions, (that would allow a slightly lower hand position compared to the pads).
IMHO- Parallel to the ground or slightly tilted up by a titch (Metric).
My bars & most of the Blue sponsored riders who had FIST bike fits ended up parallel.
"The sweet spot turned out to be exactly where John Cobb’s rule-of-thumb said it would be. "
Cobb Lesson #6 — The bottom of the forearm should be parallel to the ground to avoid pushing any air down into the legs. Like the back, the faster the air moves across the body the better. Trying to “steer” the air is counterproductive.
For John’s other rules-of-thumb: http://www.byrn.org/gtips/cobb_fit.htm
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2 years ago my bars were pointed savagely downwards. Tom D changed this and I am now more comfortable. i will say this though, for very short TT’s I used to ‘lock myself’ into position and felt incredibly powerful (I do have a strong upper body anyway but this is purely anecdotal feedback).
Now I would test any change with a power meter. If it doesn’t make much difference set them to Cobbs guidelines. If you can generate more power and you can maintain it for your proposed race distance why not ?
looking at Jans and Lances positions. I think they are mostly focused on getting their shoulders in.
I think Faris used his position for the same reason.
"The sweet spot turned out to be exactly where John Cobb’s rule-of-thumb said it would be. "
Cobb Lesson #6 — The bottom of the forearm should be parallel to the ground to avoid pushing any air down into the legs. Like the back, the faster the air moves across the body the better. Trying to “steer” the air is counterproductive.
For John’s other rules-of-thumb: http://www.byrn.org/gtips/cobb_fit.htm
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That’s apparently Gordo’s interpretation of John’s “rule”, as what he really recommends (or at least used to recommend) is that the back of your thumb never be below your antecubital fossa and the heel of your hand never be above it.
what he really recommends (or at least used to recommend) is that the back of your thumb never be below your antecubital fossa and the heel of your hand never be above it.
Uh … right. Isn’t that what I said? 
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I’m no expert, but my FIST certified fitter says downward tilt is bad: it increases frontal area, thus flat or slightly upward is better.
I totally agree with Zipp on this. I, too have my bars angling somewhat downward. I feel a significant increase in the amount of force I can pull up to stabilize my body (when needed) and it allows me to push down slightly on the bars, which gives me a degree of shock absorption. Also, if your hands are down, your natural movement makes you more aero as you slide forward, not less aero as your hands slide back. I actually require very little hand grip to stay totally aero for hours at a time. I also use s-bends in this scenario. It also might be worth saying that I have a decent amount of “drop” from saddle to aerobars pads, about (13cm/4.7in) -not sure it would work as well with a less aggressive setup.
Denis Menchov rides with his TT bars that way. Faris seems to have tried it at Kona this year, too.
http://www.cyclingnews.com/photos/2006/tour06/index.php?id=/photos/2006/tour06/tour060/40
I have little doubt that it is at least slightly less aero than a flat setup, as I can feel air flowing over my forearms. It is a power and comfort decision, and has been working well for a few years now. For me it’s about putting myself in a position that is easy for me to stay in with out choking up on my bars or having to clamp down to stay in.
I’m sure that the FIST method has some play for personal preference and comfort, no?
what he really recommends (or at least used to recommend) is that the back of your thumb never be below your antecubital fossa and the heel of your hand never be above it.
Uh … right. Isn’t that what I said?
Not exactly, as Gordo’s description makes it sound as if John is recommending a dead-level position, and only a dead-level position. Instead, he recommends a range that is centered on a slight upward tilt.
I have little doubt that it is at least slightly less aero than a flat setup
For me, the difference between having my forearms within John’s guidelines vs. having my hands just a couple of centimeters lower was about 1 s/km, or 3 min in an Ironman-distance bike leg.
EDIT for the benefit of the true aero aficianados out there:
CdA with forearms set as recommended by Cobb: 0.237+/-0.005
CdA with forearms just below level: 0.250+/-0.006 m^2
As it turns out, the difference is even bigger than I remembered, equating to ~1.3 s/km, or almost 4 min in an Ironman. In fact, changing the angle of my forearms had far greater impact on my CdA at zero degrees of yaw than varying the drop to the elbow pads from 10-11 to 20-21 cm.
As I indicated before, I also tried a greater upward angle, with my hands higher than recommended by Cobb but comparable to my position on my old Hooker. Those results were:
CdA with forearms angled upward: 0.247+/-0.006 m^2
Note: all of the above data were collected with an intermediate drop from saddle to elbow pads of 16-17 cm.
This was something that your were albe to test to that accuracy level?
Wow. How did you do it?
This was something that your were albe to test to that accuracy level?
Wow. How did you do it?
http://home.earthlink.net/~acoggan/whichisfasterthecervelop2torthejavelinarcole/
(Sorry about the missing graph and table…)
what is the difference in coefficient of drag between running a 53X13 vs a 50X14? Why such a big differnce in gearing when you are completely threading the needle on all other aspects of this test to keep things equal (bars, wheels, fork, etc)?