Do these comments apply to the TR6?
Thanks, Jim
Two '74 TR6s
-----Original Message-----
From: fot-bounces+jimhearn1=comcast.net@autox.team.net
[mailto:fot-bounces+jimhearn1=comcast.net@autox.team.net] On Behalf Of
Bill Babcock
Sent: Sunday, December 23, 2007 12:26 PM
To: Steve Belfer; Friends of Triumph
Subject: [Fot] Suspension modifications
I've had a number of people ask me about modifying the upper "a" arm
with rose
joints as I did on Peyote. I'm really hesitant to help folks do this
since you
can really screw up your front suspension and make the car more than a
bit
squirrelly. There isn't a recipe for improving the handling of a TR3/4
other
than the kind of results you should end up with. Shortening the upper A
arm to
gain camber is not a great modification, though it's common. I've
modeled this
several different ways, and it always looks ugly. I'm convinced that the
main
reason most of us wind up with stiff springs is that when the suspension
moves
it's a bad thing. With shortened upper arms you can wind up with six or
even
seven degrees of camber at full upward travel. You don't need a computer
to
show this, just pull the lower shock and spring plate and run the
suspension
up to the bump stop. You'll be horrified at how much your tire tips
inward if
you have short upper arms. The contact patch is probably a half inch
wide or
less. No wonder these cars understeer under hard cornering.
My recommendations are.
1. Buy all of Kas' books.
2. Read them.
3. Read them again.
4. Measure your camber at center, full extension and full bump.
5. Look at the rules for the organization you run with. If they allow
you to
move the upper suspension pivot point, and you're going to run radials,
move
the suspension point inward and use full length arms. You want to wind
up with
2-3 degrees of camber at the center position.
6. If you can't do that, consider small changes like using the TR6 or
Jag ball
joint.
Personally, the change I like best for TR3 suspension is using a TR6
lower
trunnion, upper arms and ball joint. It gives you three degrees of
caster and
if you really need camber adjustment you can slot the attachment bolt
holes
for the ball joint or drill alternate location holes. I'd give up a
little
camber with the suspension at ride height rather than have way too much
when
the wheel is loaded. That caster might add wear to the worm and pin
steering,
but if you're exclusively racing the car, not street driving it, that
won't
matter. Having the car stable when the steering input is light (or gone,
in my
case) is a great thing.
I've harped on this before, but the bump steer in these cars is
horrific. You
can work to eliminate that and have a car that works so much better you
won't
believe the difference. Once you do that you can soften those springs
and let
the suspension work some. Makes another huge difference.
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