<VV> Crosswind sensitivity

[Brent Covey]

Mike wrote;
>My LM convertible is very senstive to cross winds, especially with the top
up.  And that's just it, the sensitiviy is different with the two different
configurations.

I'd agree the spoiler seems mostly beneficial for reducing crosswind
sensitivity- I cant detect if ones installed at 100 mph.

Corvairs generally should be much less sensitive to crosswinds than many
cars, as the center of aerodynamic pressure on the side of the car body is
pretty close to where the car center of mass is, meaning the whole car needs
to be blown off-course rather than one end or the other as its buffeted by
crosswinds. Depending on the force and angle of the crosswind, sensitivity
should be nil to not much, theres not a very good lever for crosswinds to
disturb your course.

Another factor that really impacts crosswind performance is wheel alignment.
Lates in particular have significant 'roll steer'- as the rear suspension
compresses, it toes in slightly, which means as the car is disturbed by the
wind gusts, it tends to self correct its course proportionately. For this to
work the tires have to be aligned pretty stock- zero to positive camber,
slight toe in, and at a stock tall ride height. The rolling of the car body
will steer the rear into the wind automatically if this is exploited by your
curb settings. The front suspension uses the highish (for a sixties car)
caster setting and large scrub radius to self correct for 'fishtail' sort of
motions as well, tending to stabilize the cars course. The car rolling tends
to load the steering towards a straight ahead path. If you've ever got the
tail of a Corvair loose on a gravel road swinging side to side, you've
probably noticed the car will make corrections rapidly as it bounces to
reach equilibrium on its own if you let the steering wheel slide thru your
fingers.

I think the different behaviour of some quite similar cars with no apparent
differences in configuration can mostly be traced to alignment details.
Running too low a ride height with negative camber on the rear wheels and
low caster on the front is a lot more sensitive to crosswinds. This probably
explains why some cars seem very insensitive to them, and other nearly
identical Corvairs are very tedious to drive in windy conditions.

Brent Covey
Vancouver BC