What are the areas on a bike that would reduce drag should an item fill that space?
For example, windtunnel tests tell us that a BTA bottle will decrease drag. I’ve seen claims that aero bottles on the frame reduce drag. Are those the only places that it’s beneficial to fill in that space with equipment? How about a bento box? Do behind the seat bottles and flat kits do the same? Would covering the hollowed out seat do anything?
How about on the rider? What are the areas that produce the most drag? What reduces (or improves) these areas?
With regards to the frame “filling in space” does not guarantee that the frame will be faster. An active member on this board, DarkSpeedWorks, was fabricating a flat-kit that filled in the lower part of the Cervelo P5 frame. The first version did surprisingly poorly in the wind tunnel… especially for something that “looked” fast (I was shocked frankly).
For some people, aero bottle on the down-tube/seat-tube are faster. For others it’s not. There’s no hard/fast rule. I recall from the aero camp thread one woman was actually faster with two round bottles on her frame. An outlier, sure, but it shows you that aero outcomes are variable. There are few hard rules. There are, however, some rules of thumb:
-Getting lower up front (spine angle) will make most people more aerodynamic
-Getting narrower up front (between the arms) will make most people more aerodynamic
-Lowering the head will make most people more aerodynamic (this is actually close to a law)
-If used for a flat kit, a round bottle will have less of a drag penalty behind your seat than on your seat tube or down tube
-Shaving your legs is good for a decent wattage savings
Equipment choices
-tight fitting sleeved tri suits test faster than bare skin quite regularly
-while not always the fastest, a properly sized Giro Advantage 2 is often within a few watts of the fastest helmet for a rider
-sunglasses + helmet is almost always faster than helmet + shield… I’ve seen maybe one exception to this rule in all of the wind tunnel reports I’ve read.
-a rear disc is pretty much always the fastest/best choice.
-basebar choice is often nearly as important as frame choice
-keeping your cables out of the wind is always a good choice
Thanks! Good info. I like to think that most of that is addressed when I ride. The biggest thing is prob getting lower, should that be optimal. Will have to test to see if that’s the case.
