Aero and gears are different, but I do
understand what you are saying about
tailoring both so you don't have to lift.
In measuring differences and changes,
you need to be careful about combining
changes and trying to measure the results
of each one.
If the gears are more-or-less evenly spaced,
it will be better to be near redline in a
particular gear at the end of the longest
straight as opposed to having just shifted
into that gear shortly before the end of
the straight. Here the shorter gear (R&P)
helps.
On the infield of Fontana, having a shorter
R&P might help by allowing you to keep in
the power band. There are some corners that
are slow enough that it kinda bogs down, yet
you don't wat to downshift.
But other tracks it can hurt. Spring Mountain
in the two big sweepers, you might find that
with the shorter R&P you need fourth instead
of third, now the car doesn't pull out of the
corner as well as it did in third.
Compare my '78 SC (Butch) with the 7:31 R&P
versus the stock 8:31 from a rolling 50mph
start over a 1000 ft and 1500 ft straighaway;
7:31 R&P
1000ft 8.46 sec @ 102.8mph
1500ft 11.62 sec @ 115.6mph
8:31 R&P
1000ft 8.41 sec @ 103.8mph
1500ft 11.50 sec @ 114.7mph
See how close they are? The 8:31 has a very
slight advantage, but this could easily be
offset by having an awkward rpm/gear range
somewhere else on the track, which is most
likely the case for a number of us.
Of course the 7:31 will get you from zero
to 50mph (and beyond) more than 0.3 second
quicker than the 8:31, which is a huge
advantage for autocross.
In real-world driving Butch on tracks, the
8:31 feels and measures just as good as the
7:31, although I do shift at different points.
Tailoring the gearbox for a particular track
will help a bit, but I can't drive consistently
enough to really take advantage of this. I do
know that bumping off the rev limiter for half
the straightaway is not as fast! And I also do
know that there are a number of tracks where
the taller gearing feels awkward in several
corners, so that is definitely a factor.
And, at Fontana in Snickers (the '79 SC),
I see 6600rpm in 5th with 8:31 and 23.0"
rear tires. That's 142mph, and although
the car is still pulling, it is not pulling
by very stinkin much - it would take a lot
longer stretch to get even a few more mph
out of it. With a 7:31, it would be at
rev limit at 135mph before turn one.
I just feel that for Time Trials, six points
might be better spent elsewhere, but then it's
not my six points.