Re: turning circle, Ferrari (some Alfa content)

[Sonny <maxid@xxxxxxxxxxxxxx>]

The discussion of Ferrari turning circles got me curious, so I poked aruond a
little. A Ferrari Maranello has a 13.8 steering ratio and a 39.3 ft/12.2 m
turning circle. A ratio of 13.8 means that to turn the road wheels 1 degree,
you have to turn the steering wheel 13.8 degrees. This is one of the quickest
steering racks on a production car. My casual observation indicates that
ratios from 15-19 are common on contemporary cars with power-assisted steering
(non power-assisted cars generally have higher ratios). Alfa 156 and other
modern Alfas have some of the quickest ratios around, in the same range as the
Ferrari. Custom racks with even quicker ratios are available from tuners, but
they are unsuitable for road use, as a brief lack of concentration may land
you in the ditch, or worse. In my opinion, steering ratio is a more
informative number than turns lock-to-lock because it directly reflects the
steering feel of a car. Turns lock-to-lock is influenced by the limits of
wheel travel (~turning circle) in addition to quickness of steering.

For a number of years, variable-assist power steering has been common; i.e.,
the amount of assistance decreases with engine rpm or vehicle speed with the
intent of stabilizing the car during highway travel. More recently,
variable-ratio has also become common; the ratio of the rack varies between
the center and either extreme. When only one number is given for the steering
ratio of such a car, it is the ratio at center.

Older Ferraris without power steering may have had slower steering to offset
high steering input demands due to large tires, but I don't think Ferraris in
general have particularly slow steering. It appears to me that other sporty
cars have surprisingly large turning circles (Subaru WRX STi and Mitsu Lancer
EVo come to mind; both have _quick steering_ though), but it is my guess that
the large turning circle is mandated by technical consideratins of some kind,
not including the manufacturer wanting "to limit the number of turns
lock-to-lock"...what would be the value of that?

Sonny
91 164 S
Baltimore
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