The majority of the drag affecting a modern HPV racer is caused by the wheel aperture. Perfectly fitting the fairing to the tyre isn't practical, due to flex in the wheel and the tyre casing. Managing airflow around this gap is a largely unsolved problem.

Some improvements could be made by reducing the rolling resistance of the tyres or the efficiency of the drivetrain, but this will have only a relatively small impact; this drag increases linearly with speed, whereas aerodynamic drag increases geometrically.