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The Iron Duke Resource Site



Welcome to my newly redesigned Fiero 2M4 resource site.  The original site recorded over 12000 visits,  hopefully this one will also prove as useful.
Ira Crummey

Road Hugging Weight:
The Myth
The greater the vertical load on a tire the greater its friction with the surface, therein lies the myth of road hugging weight.

If you add mass to a car you first of all increase its momentum at any given speed.  Increased momentum also implies a greater tendency to continue in motion in a straight line, inertia.  This tendency quickly counteracts (and overpowers) the increased friction afforded by the increase in vertical tire load caused by the mass increase.  Additional mass is not without its advantages in certain automotive applications but handling response and cornering power are not among them.

Tires produce proportionally less increase in traction as vertical load increases.  This also flies in the face of the road hugging weight myth since the mass increase soon overtakes the traction increase and reduces lateral acceleration.

Vehicle aerodynamics were in there infancy in the 1960s.  Experimentation was constant and new ideas were coming along almost daily, among these ideas would be the most effective method of mounting a downforce wing.  The Chaparral racers pioneered a high mounted wing which was mounted to the hub carriers rather than the chassis, soon Formula 1 racers were appearing with front and rear adjustable wings mounted high above the car on struts which mounted in the same way.   Here we have the perfect solution, aerodynamic downforce is applied directly to the wheels increasing the tire's vertical loading tremendously, however the mass of the car is not increased so the momentum is not increased.   All of the vertical load translated into increased lateral acceleration since there was no mass increase.  The cars could use softer suspension settings which made them ride better and cause less fatigue for the driver.  The system was short lived however since it was seen as a safety hazard by some.  The extreme stress on the hubs and the sudden loss of grip if a wing strut broke were cited as major negatives.  Modern Formula 1 race cars use body/chassis mounted wings, this means the force is now transmitted into the entire car, causing the springs to compress resulting in the need for ridiculously high spring rates.  This is why you can see these cars bounce one wheel off the pavement when a bump is encountered.

Wings on street vehicles, such as the Fiero GT wing,  serve little or no function in downforce.   The Fiero wing does however smooth the airflow over the rear of the car and reduces aerodynamic drag.  Spoilers do work at lower speeds.  A spoiler changes airflow over a surface in order to prevent lift.  The moral of this little story is forget about road hugging weight, lighter is better,  and wings may look cool but are only effective if they are large and in the airflow, or at very high speeds.
Ira Crummey


FIAT 850 SpiderAn example of a nimble, light weight sports car of a simpler time.