I devote a lot of thought to this topic.
There is an commonly held belief that a lower bike position, especially in the front end, is faster.
This is based on the supposition that a low body position is more aerodyanmic and has lower drag (same thing).
The problem with this thinking is that it is myopic and does not consider the entire envelope of performance within which a triathlete races a bike.
Let's consider these ideas: Dave is a strong age group triathlete who can average 22 m.p.h on a rolling triathlon bike course. To average this 22 m.p.h. he will ride at speeds that vary between a maximum of 34 m.p.h. on a moderate descent in light winds to only about 12 m.p.h. on the toughest climb on the course. At the top end of the envelope (34 m.p.h.) aerodynamics is an important consideration along with stability (influenced in part by frame geometry and rider weight distribution). At the bottom end of the envelope (12 m.p.h.) aerodynamics is a greatly diminished factor. Power output and the biomechanical features of the rider's position on the bike become the predominant determining factor in speed a the lower end of the envelope. This is critical because, assuming the course ends where it starts (net elevation gain/loss is zero) Dave will spend more time grinding up a hill at 12 m.p.h. than speeding down it at 34 m.p.h.
This only speaks to the opposite ends of the envelope; fastest and slowest. It's the middle where the most gains will likely be made since that is where you spend most of the time overall- in the middle of the speed envelope.
In the center of the speed envelope a balance of aerodynamics, handling (stability, being able to look up the road comfortably, being able to corner at speed, being able to use water bottles and reach jersey pockets for nutrition) and power output will result in the optimal performance. If any one element is out of balance the position isn't optimized over the entire distance.
We frequently see the thinking that "I need to get lower to go faster". This may not make you faster. It may make you slower in the real world.
When people look at Lance Armstrong's time trial position
They often remark at how high and rounded his posture looks. He may be the most wind tunnel tested athlete in history. He is also one of the athletes to use power measurement as a basis for setting up his position.
The axiom that seems to have risen from the integration of power output data and wind tunnel data is that you should never sacrifice one watt of pawer output to save one gram of drag.
The use of the vernacular "aggressive" usually is used to describe a lower position as though it is somehow overall faster. Often times it absolutely is not.
I'd sure like to hear people say things like "I want to get my position more efficient" than hearing them say, "I want my position to be more aggressive".
I'm interested to read your thoughts and comments.
Tom Demerly
The Tri Shop.com
There is an commonly held belief that a lower bike position, especially in the front end, is faster.
This is based on the supposition that a low body position is more aerodyanmic and has lower drag (same thing).
The problem with this thinking is that it is myopic and does not consider the entire envelope of performance within which a triathlete races a bike.
Let's consider these ideas: Dave is a strong age group triathlete who can average 22 m.p.h on a rolling triathlon bike course. To average this 22 m.p.h. he will ride at speeds that vary between a maximum of 34 m.p.h. on a moderate descent in light winds to only about 12 m.p.h. on the toughest climb on the course. At the top end of the envelope (34 m.p.h.) aerodynamics is an important consideration along with stability (influenced in part by frame geometry and rider weight distribution). At the bottom end of the envelope (12 m.p.h.) aerodynamics is a greatly diminished factor. Power output and the biomechanical features of the rider's position on the bike become the predominant determining factor in speed a the lower end of the envelope. This is critical because, assuming the course ends where it starts (net elevation gain/loss is zero) Dave will spend more time grinding up a hill at 12 m.p.h. than speeding down it at 34 m.p.h.
This only speaks to the opposite ends of the envelope; fastest and slowest. It's the middle where the most gains will likely be made since that is where you spend most of the time overall- in the middle of the speed envelope.
In the center of the speed envelope a balance of aerodynamics, handling (stability, being able to look up the road comfortably, being able to corner at speed, being able to use water bottles and reach jersey pockets for nutrition) and power output will result in the optimal performance. If any one element is out of balance the position isn't optimized over the entire distance.
We frequently see the thinking that "I need to get lower to go faster". This may not make you faster. It may make you slower in the real world.
When people look at Lance Armstrong's time trial position
They often remark at how high and rounded his posture looks. He may be the most wind tunnel tested athlete in history. He is also one of the athletes to use power measurement as a basis for setting up his position.
The axiom that seems to have risen from the integration of power output data and wind tunnel data is that you should never sacrifice one watt of pawer output to save one gram of drag.
The use of the vernacular "aggressive" usually is used to describe a lower position as though it is somehow overall faster. Often times it absolutely is not.
I'd sure like to hear people say things like "I want to get my position more efficient" than hearing them say, "I want my position to be more aggressive".
I'm interested to read your thoughts and comments.
Tom Demerly
The Tri Shop.com