In reply to a message from Kirbert sent Thu 30 Nov 2006:
Kirby, I may not be 100% here, but I think the Sport Pack rear bar
is 5/8ths.
I have 7/8ths on the rear of my street car and the 1 in. in the
front, the thing will corner like on rails.
Chadbourn Bolles
803 798 3044–
Dr. Chadbourn Bolles
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Gordan Bobic wrote:
I was talking about stiffening up the radius arm bushes. Putting
hard bushes on the radius arms, or turning the standard ones
through 90 degrees will only lead to the top subframe mounts
failing quicker.I kinda doubt it. Seems to me stiffer bushings, or turning the
standard forward bushings 90 degrees, will help hold the subframe
more securely and apply less stress on the subframe mounts.Not at all. Think about how the components are arranged. The lower
whishbones have to move up and down - that’s kind of fundamental to
the suspension. As they do, they are moved forward and backward by the
fact that the radius arm is anchored to them, and is describing the
arc. The distance between the whishbone and the radius arm anchoring
point is L * cos(A), where A is the angle the the radius arm, and L is
the length of the radius arm.Either the radius arm bushes or the subframe mounts have to give.
All true. However, it is my suspicion that the subframe mount flex
due to the arc of the radius arm is minor compared to the subframe
mount flex that occurs when you drop the hammer in 1st gear. To my
knowledge, everyone that’s had issues with the subframe mounts
reported that they failed when doing hole shots, not when the car was
jacked up (which is when the arc of the radius arm does its worst).
Since stiffening the bushings at either end of the radius arm will
reduce the amount of subframe motion due to hammering the throttle in
low gear, I suggest it would reduce the stresses on the subframe
mounts, not increase them.
Stronger anti-roll bar will spread the load between the two sides,
which may or may not make this worse.I dunno what load will be spread between the two sides. Without the
anti-sway bar, the car leaning may stress the subframe mounts on one
side in compression and the mounts on the other side in tension, and
the anti-roll bar would be expected to reduce both stresses.Not quite. The radius arms make the subframe twist horizontally when
vertical twisting (i.e. car leaning into a corner) is applied.
Since the suspension travel is at a different extension on each side,
the radius arm on one side is pulling the subframe farther forward
than the radius arm on the other side, distorting the subframe
mounts. Yeah, I see that. But adding an anti-roll bar would reduce
it.
Basically, it’s transferring some of the anti-roll stress from the
weak subframe mounts to the rugged anti-roll bar mounts.Sort of, but in that case you should probably waste less time with
anti-roll bars and start by replacing the subframe mounts with solid
steel brackets, and get rid of the radius arms all together.
Not sure what this had to do with the point about the anti-roll
stress moving to the anti-roll bar mounts.
Of course, that lockdown (and simplification) of the Jaguar IRS is
exactly what the Cobra guys do. It does make a fundamental
difference in the suspension geometry, taking it from having entirely
too much rear-end steering to having none at all.
If the
idea is to restrict suspension movement, bigger anti-roll bars while
all those rubber mounts are there are a bit like polishing the
silverware on the Titanic.
I think that was my point at the beginning of this discussion. I
found the OEM 9/16" bar did just what I wanted done, but if you’re
installing that ADDCO monster, I’d think a full set of poly bushings
all around – front and back – would be in order.
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…I was talking about stiffening up the radius arm bushes. Putting hard
bushes on the radius arms, or turning the standard ones through 90 degrees
will only lead to the top subframe mounts failing quicker…-----Original Message-----
From: Gordan Bobic
I tried a different approach on my car. Rather than stiffen any of the
bushings, I figured it might make more sense to attach the sway bar to the
suspension in a more rigid location. In most cars, including the Jag on the
front suspension, the swaybar is attached to the lower suspension member
directly. So, along that reasoning, I welded a swaybar attachment point to
each lower suspension link. That way, the force of the bar is not acting
through the radius arm bushing, but on the lower link directly. I have put
about 10K miles on the car since I made this modification, and am very
pleased with the results. While the car is very neutral in hard cornering,
it does not seem overly stiff. Also, since the existing suspension geometry
has not changed, it still rides very much like the original car when not
being pushed. I have posted pictures of the installation, along with some
of the other modifications I’ve made at:
http://home.windstream.net/colin_smith/jaguar.html
C.Y. Smith
'89 XJ-S Convertible
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In reply to a message from C.Y. Smith sent Fri 1 Dec 2006:
C.V. if it is alright with you I am going to use your Electromotive
info on a Lamborgini site, where some people have said the system
is a pice of shi*
My responds to them was they were tooooooooo lazy to set the system
up corrtly. I told them they expected to take something out of a
box and have it work with no work on their part. They said they had
some of the best people you could find work on it and could not
make it work.
I did have the same system on my XJ-S and never had a problem.
Regards
Chadbourn Bolles
803 798 3044–
Dr. Chadbourn Bolles
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C.Y. Smith wrote:
Rather than stiffen any of
the bushings, I figured it might make more sense to attach the sway
bar to the suspension in a more rigid location.
Yup.
In most cars,
including the Jag on the front suspension, the swaybar is attached to
the lower suspension member directly.
Actually, I installed an ADDCO bar on a Volvo wagon once in which the
bar bolted directly to the trailing arms. And only to the trailing
arms, there were no center bushings or brackets. But those trailing
arms were rigidly attached to the rear axle, not via soft bushings.
So, along that reasoning, I
welded a swaybar attachment point to each lower suspension link. That
way, the force of the bar is not acting through the radius arm
bushing, but on the lower link directly. I have put about 10K miles
on the car since I made this modification, and am very pleased with
the results.
Just outta curiosity, did you have the same anti-roll bar connected
up conventionally before? Can you provide a comparison between the
two attachment schemes using the same bar?
While the car is very neutral in hard cornering, it does
not seem overly stiff.
What size bar are you using? And while we’re at it, what size tires
are you running?
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…Just outta curiosity, did you have the same anti-roll bar connected up
conventionally before?..-----Original Message-----
From:Kirbert
I never had a sway bar in that car before that, so I can give you any
comparison data
…What size bar are you using? And while we’re at it, what size tires
are you running?..
I used 7/8" bar in the rear and a 1-1/16" in the front. I’m running 245/45
VR 18 tires on BBS wheels
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In reply to a message from Dr. Chadbourn Bolles sent Fri 1 Dec 2006:
Hi Chad,
Have you welded the mounts on your street car? or used urethane
Regards
Don–
The original message included these comments:
I have 7/8ths on the rear of my street car and the 1 in. in the
front, the thing will corner like on rails.
–
D W ANDERSON
SINGLETON NSW, Australia
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In reply to a message from dwa sent Mon 4 Dec 2006:
I welded the rear subframe mounts. Jacked the car supported the
assy, then welded the mounts.
I had solid mounts on the front of the front ‘‘K’’ member on my 83
street car. That car cornered like on rails.
On the race car the front ‘‘K’’ member has solid mounts at the rear
and aluminum solid mounts in the front. The rear has the mounts
welded solid. This helps but I still get wheel hop if I use too
much power in 1st or 2nd gear. Once up to speed in 1st, like around
7000 rpm, I can use 2nd with no problem. I might go to a 4 link
suspension in the car if with the new engine, I cannot control
wheel hop. This years engine should be in the 600 HP range, so I do
look for problems.
Chadbourn Bolles
803 798 3044–
Dr. Chadbourn Bolles
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In reply to a message from C.Y. Smith sent Mon 4 Dec 2006:
Where did you get the 1 1/16’’ bar? I would like one of them
for myself… any possibility of 1 1/8’'? 
Also need another 7/8’’ rear bar, but that’s easy to obtain.–
The original message included these comments:
I used 7/8’’ bar in the rear and a 1-1/16’’ in the front. I’m running 245/45
VR 18 tires on BBS wheels
–
-Ted – '92 XJS V12 5-speed
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…Where did you get the 1 1/16’’ bar? …-----Original Message-----
From: TedDuPuis
I got mine from Gran Tourismo Jaguar, who are now out of business, and I
don’t remember hwo actually made the bar. I’ll check around and see if I
can find out.
C.Y. Smith
'89 XJ-S Convertible
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