I will give my 2 cents on this topic even tho I have not yet driven a
big TR with the 5 degrees of + caster I like. My 4A will get there.
The obvious benefit of better straight line stability is not as useful
to high performance driving as the benefit to camber gain. You can get
the cornering camber you want partially thru upper arm angle, tho this
gets the front suspension acting more like a swing axle than we would like,
partially thru static camber angle, tho this can be detrimental to tire grip
under hard brakeng. Caster, on the other hand, has only increased steering
effort as a bad side effect. BMW has used lots of caster in its power
steering equipped sedans to minimize camber loss in roll. We did some
set up work on an old studebaker based sports racer a few years ago.
One of the things that is hard to do on their old kingpin setup is get caster
adjustment, so we put wedges under the rear of the lower control arm shaft
and raked the whole business back. We found that at about 5degrees of
+ caster, we no longer had a camber loss as the suspension went thru its
bump travel and steering movement. On the test track the road feel was
much improved and as cornering loads increased, so did the steering effort.
It never got oppressive, but it was there.
Bill Boemler told me that he put together a setup for his TR3 racer that
had about 12 degrees of + caster. When I asked him how it worked, he
replied, "It went around corners better than it ever had and after eight laps,
my arms fell off!"
art de armond
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