Bluebottle wrote:I don't know much about the Sierra issue other.
These things happen regularly and it isn't always the aerodynamicists fault. Sometimes some bright spark decides he doesn't like that bit of trim being there or the shape of the wheel arch etc and buggers the airflow without realising.
I am not arguing that he isn't to blame - I don't know.
You also get unexpected side afffects from the shear complexity of what the air is doing and some carefully thought out flow management doesn't work because something else generates greater/weaker forces somewhere else or something only happens in a certain situation (folloing a HGV with a specific side wind and airspeed).
I used to be a motor machanic back then and we got the trade articals about it but I found this on wiki
http://en.wikipedia.org/wiki/Ford_Sierra
Early versions suffered from crosswind stability problems, which were addressed in 1985 with the addition of "strakes" (small spoilers), on the rear edge of the rubber seals of the rear-most side windows.
I look forward to reading more - thanks for putting the time in


