Went out to ride a local TT last night, the pre event conversation inevitably turned to equipment. There was a bewildering array of frames, wheels and helmets on display, it’s clear that us cyclists can get a little obsessed.
The impressive speeds accomplished by a rider mean that the rewards for achieving aerodynamic efficiency are substantial.
Between 70 and 90 per cent of a rider’s power output is used to overcome air resistance. A great deal of brainpower and R&D dollars are therefore invested each year in finding the best ways to reduce drag as the sport gets closer to the limit of how much power a rider can produce with legs alone.
A rider has to overcome wind resistance in two forms: air pressure drag and surface friction.
Air pressure drag is caused when a shape that is irregular and bulky (such as a human body on a bicycle) moves through the atmosphere creating turbulent airflow and leaving low pressure areas in its wake. With higher pressure in front and lower pressure behind a rider is ‘pulled’ back and has to apply exponentially more power to keep accelerating to higher speeds. This is the primary cause of aerodynamic resistance in cycling.
Surface friction is the direct ‘rubbing’ of the air against the outer surface of a rider and bike. This is less of an issue than air pressure drag but can still be significant, especially at high speeds, which is why skin suits and smooth finishes on components are used by many cyclists.