In a TR-4, solid axle, in my experience the use of a rear bar depends
on the type of limited slip diff as well as spring rates. Plus, if
you've improved the front suspension geometry everything changes,
probably. With a Quaffe LSD, keeping both rear tires on the ground
is vitally important. We ended up removing the rear bar primarily to
keep the inside rear on the ground. We were loosing more speed by
lifting a wheel than we could have gained by the improved
handling. What we then discovered is that due to the funky roll
centers of the TR-4 fitting a really large front bar actually made
the car rotate better through the corner. The conventional wisdom is
that increasing the front spring rate - either with springs or sway
bar - will increase understeer. That's not entirely true in the
solid axle TR-4. We have stiffer front springs and an extra leaf in
the rear. Babcock's explanation finally made the light bulb go off
in my head, and it explains the pictures we have of our cars with the
inside front tire hiked up in the air.
My car (John Lye's former autocrosser) came with a substantial rear
bar, a substantial front bar and stiffer springs all around. It also
has a detroit locker in a non-triumph rear axle. I also found at the
last race that all of the corner weights are within 5 lbs of each
other with half a tank of gas. I'm sure it rotated VERY nicely on
the auto-x course! When I had it at speed at Road America, I had
this wonderful sideways drift / slide through all of the corners -
but was giving up like 5 sec / lap. I disconnected the rear bar and
it still tends to oversteer, but is about perfect. The locker acts
like a welded diff when ON the power and kinda like an open diff when
OFF the power. You can still roll the car around, and turn-in under
braking is like an open diff. I tend to be on the gas hard well
before the apex and kinda dirt track it through the corner. But I
don't seem have that welded diff initial understeer to overcome.
There's also the soft spring / stiff sway bar school of thought - I
haven't traveled that path so can't comment on what you need to do
with sway bars if you don't hike the spring rates. Also, haven't
tried tuning a car with a Salisbury LSD.
- Tony
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