Quote:
Originally Posted by JulianEdgar
Stability is a bit more complex than is being described.
1) If rear lift is higher than front lift, the car will be more unstable - so it's not just the absolute values but also the ratio of lift values. Recent papers from Porsche describe this very well.
2) Lateral stability depends largely on the lateral locations of the centre of pressure versus the centre of gravity, with a rearwards centre of pressure required for stability. (ie more side profile area towards the back of the car than the front.)
Re the Sierra, I haven't explored it in detail but I understand that they added separation edges to the sides of the rear glass to improve stability, so perhaps there was an oscillatory flow at those locations.
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The adjoining issue with F/R ratios is additionally, there is seldom an aero system in place that the ratio remains constant over the useful speed band. Meaning one has to compromise and try to remain within the band where the stability is acceptable, to state the obvious,