[xj-s] Anti-roll bar kit - buying advice

There is a vendor on ebay - located in the USA - selling an
anti-roll bar kit (links, polyurithene bushes, nuts etc) at
a reasonable price. Has anybody used them and if so, OK

Thanks–
Paul Kiver
Isle of Man, United Kingdom
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In reply to a message from Paul Kiver sent Tue 28 Nov 2006:

If you are talking about The DrivenMan, yes I have bought the kit.
It is one of the best bolt on improvements that I have made to my
car!

Scott–
1986 XJS 5.3 Coupe
Commack, New York, United States
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In reply to a message from Paul Kiver sent Tue 28 Nov 2006:

Classic Spares are probably the best source of anti-roll bar
kits and other suspension improvements for the XJS. They can
provide HBE kits and other options and have the depth of
knowledge to provide excellent support and advice.

Contact Ray Ingman at:-

info@classicsparesltd.co.uk
Tel: 01992 716236–
Roger Bywater / AJ6 Engineering
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In reply to a message from Paul Kiver sent Tue 28 Nov 2006:

On my ‘82 XJ-S, I used Addco anti-roll bars. 1’’ front, 7/8’’ rear. I
found that the pair made a fabulous improvement in the car’s
performance. I don’t know how much the vendor is charging, but you
can probably get them cheaper if you shop around. Addco will
frequently sell you the anti-roll bars directly for a reasonable
cost. Being in the UK, though, I think your biggest cost would be
shipping.–
-Ted – '92 XJS V12 5-speed
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In reply to a message from TedDuPuis sent Wed 29 Nov 2006:

Did any of you guys find a stiffer ride after the rear bar was
installed? If so…was the trade off worth it?–
Rob Wade
Windsor Ontario, Canada
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In reply to a message from Rob Wade sent Wed 29 Nov 2006:

The ride is not stiffer, but when you corner, WOW what a difference.
If you want to know about pricing for ADDCO, call me.
Chadbourn Bolles
803 798 3044–
Dr. Chadbourn Bolles
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In reply to a message from Rob Wade sent Wed 29 Nov 2006:

No stiffer ride. Anti-roll bars won’t stiffen your ride
because they don’t change the rate at which your wheels can
move. They just change how one side can differ from the
other. So when you go to turn, the car is flat through the
corners.

The front is a fairly straightforward installation, however
it requires dropping the front subframe a few inches to get
the old bar out and the new one in. This means that it
becomes a very good time to replace your front subframe
bushings/donuts if they’re bad.

The rear requires removal of the trailing arms, and also
requires that you either modify your trailing arms or obtain
trailing arms from an XJ-S that had a factory rear anti-roll
bar.–
The original message included these comments:

In reply to a message from TedDuPuis sent Wed 29 Nov 2006:
Did any of you guys find a stiffer ride after the rear bar was
installed? If so…was the trade off worth it?


-Ted – '92 XJS V12 5-speed
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In reply to a message from Rob Wade sent Wed 29 Nov 2006:

Another thing I was wondering about was the possibility of
getting a larger front bar… something like a 1 1/8’’ or a 1
1/4’’. My Town Car has Addco bars front and rear, 1 1/4’’
front and 1’’ rear, and the thing handles like you wouldn’t
believe. Certainly doesn’t turn like a boat. The Jaguar is a
big heavy car as well, and I think that it would benefit
from a bar larger than 1’’ in front. I wonder if Addco would
be willing to make a set of bigger anti-roll bars if we got
some people together. Anyone else interested?–
-Ted – '92 XJS V12 5-speed
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Stiffer only when going around a corner, or if one wheel hits a bump and the
other doesn’t.

Adding/upgrading anti-roll bars has been one of the first things I’ve done
on nearly every car I’ve owned…

Doug Dwyer
Longview Washington USA
1995 XJR
1988 XJS V12 Coupe

Did any of you guys find a stiffer ride after the rear bar was
installed? If so…was the trade off worth it?

// please trim quoted text to context onlyFrom: “Rob Wade” robsxjs@hotmail.com

Yes, I had to source the OEM bracketed arms and hardware to use the Addco
bar. Some of the other kits I’ve seen out there include hardware which makes
this unnecessary

Doug Dwyer
Longview Washington USA
1995 XJR
1988 XJS V12 Coupe

The rear requires removal of the trailing arms, and also
requires that you either modify your trailing arms or obtain
trailing arms from an XJ-S that had a factory rear anti-roll
bar.

// please trim quoted text to context onlyFrom: “TedDuPuis” tdupuis@gmail.com

Doug Dwyer wrote:

Stiffer only when going around a corner, or if one wheel hits a bump
and the other doesn’t.

Adding/upgrading anti-roll bars has been one of the first things I’ve
done on nearly every car I’ve owned…

Ditto.

About the rear anti-roll bar on the XJ-S: It almost doesn’t matter
what size bar you use, because the way it’s normally connected to the
suspension is via the trailing arm. The trailing arm is attached to
the swingarm via a really squishy rubber bushing which soaks up most
of the effect of a stiff bar. I used an OEM 9/16" bar on my '83 and
was very happy with the results, but if you’re looking for stiffer
yet you’ll probably need to either change the attachment scheme or
replace those soft bushings with stiffer poly bushings to attain any
serious anti-roll effect at the rear. The 7/8" bar offered by Addco
would be WAAAAY too stiff for this car if it weren’t for those
bushings soaking up their action.

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TedDuPuis wrote:

Another thing I was wondering about was the possibility of
getting a larger front bar… something like a 1 1/8’’ or a 1
1/4’’. My Town Car has Addco bars front and rear, 1 1/4’’
front and 1’’ rear, and the thing handles like you wouldn’t
believe. Certainly doesn’t turn like a boat. The Jaguar is a
big heavy car as well, and I think that it would benefit
from a bar larger than 1’’ in front.

I’m sorry, but it’s not the weight of the car that matters. It’s the
height of the center of gravity, the suspension geometry, and the
geometry of the anti-roll bar itself.

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Good point about the bushings, etc.

I first had an OEM rear bar and then went to the 7/8" Addco. Against
conventional wisdom I did not increase the size of the front bar. Anything
short of all-out, madman-with-your-hair-on-fire driving it feels great but,
not surprisingly, it definitely wants to oversteer if pushed right to
the limits. And the limits are pretty high so you can really have a mess on
your hands if you’re not on the ball.

So, if your the type of person who prefers seeing what you’re about to crash
into, don’t do what I did :slight_smile:

Doug Dwyer
Longview Washington USA
1995 XJR
1988 XJS V12 Coupe

The trailing arm is attached to
the swingarm via a really squishy rubber bushing which soaks up most
of the effect of a stiff bar. I used an OEM 9/16" bar on my '83 and
was very happy with the results,

The 7/8" bar offered by Addco
would be WAAAAY too stiff for this car if it weren’t for those
bushings soaking up their action.

// please trim quoted text to context onlyFrom: “Kirbert” palmk@nettally.com

Kirbert wrote:

About the rear anti-roll bar on the XJ-S: It almost doesn’t matter
what size bar you use, because the way it’s normally connected to the
suspension is via the trailing arm. The trailing arm is attached to
the swingarm via a really squishy rubber bushing which soaks up most
of the effect of a stiff bar. I used an OEM 9/16" bar on my '83 and
was very happy with the results, but if you’re looking for stiffer
yet you’ll probably need to either change the attachment scheme or
replace those soft bushings with stiffer poly bushings to attain any
serious anti-roll effect at the rear.

The only problem is that because of the way the rear suspension hangs
together, if you stiffen up the radius arm bushes, you’ll end up tearing
off the radius arm mounts out of the chasis, and tearing up the subframe
mounts. The whole point of the rear suspension setup was to provide
passive steering at the back when the car leans into a corner. If you
are stopping the car from leaning into the corner, all you are doing is
tearing up the rubber bushes.

Gordan

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In reply to a message from Kirbert sent Thu 30 Nov 2006:

OK, here’s a question: When looking at bar choices, the rear
choices have invariably been the stock 9/16 bar offered on the
early cars, or the 7/8 bar from Addco or HBE. A peak in my latest
XKs catalog reveals mention of a 3/4 bar for the rear as a special
order, targeted specifically at convertibles and cabriolets.
Anyone know anything about that?–
Mike, 1990 5.3 XJS Convertible, ‘Caterwaul’
Lakewood, OH, United States
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mike90 wrote:

OK, here’s a question: When looking at bar choices, the rear
choices have invariably been the stock 9/16 bar offered on the
early cars, or the 7/8 bar from Addco or HBE.

Yeah. And for those unaware, the stiffness of an anti-sway bar
varies with the 4th power of the diameter, so a 7/8 bar is more than
five times as stiff as a 9/16 bar. It’s not like these are just a
little bit different, they are RADICALLY different. It’d be really
nice if there were more choices in between.

A peak in my latest XKs
catalog reveals mention of a 3/4 bar for the rear as a special order,
targeted specifically at convertibles and cabriolets. Anyone know
anything about that?

First I’ve heard. I actually think a 5/8 would probably be a better
seller, being significantly stronger than the OEM 9/16 (about 50%
stiffer) but not so stiff as to compromise the comfy ride of the XJ-S
all that much.

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I speculate that the A/R bar builders want to make darn sure the customer
feels a really, really big difference :slight_smile:

Doug Dwyer
Longview Washington USA
1995 XJR
1988 XJS V12 Coupe

Yeah. And for those unaware, the stiffness of an anti-sway bar
varies with the 4th power of the diameter, so a 7/8 bar is more than
five times as stiff as a 9/16 bar. It’s not like these are just a
little bit different, they are RADICALLY different. It’d be really
nice if there were more choices in between.

First I’ve heard. I actually think a 5/8 would probably be a better
seller, being significantly stronger than the OEM 9/16 (about 50%
stiffer) but not so stiff as to compromise the comfy ride of the XJ-S
all that much.

// please trim quoted text to context onlyFrom: “Kirbert” palmk@nettally.com

Doug Dwyer wrote:

I speculate that the A/R bar builders want to make darn sure the
customer feels a really, really big difference :slight_smile:

Agreed. I suspect they also consider their customers to be the
serious performance guys who don’t wanna go halfway, they want the
max! More is always better, isn’t it?

Man, I ran into that trying to install a moderate rear bar in my
Civic. The Civic tuner crowd can’t even comprehend anything
moderate. If it’s not over the top, why bother?

Still, there is yet one more factor at work here. The early XJ-S
came with the 9/16 rear bar. Apparently ADDCO has been laboring
under the assumption that they all came with a 9/16 bar – so why
would they offer a light bar? This also explains why their kit
apparently still doesn’t include attachment hardware, presuming you
already have it.

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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.

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.
Basically, it’s transferring some of the anti-roll stress from the
weak subframe mounts to the rugged anti-roll bar mounts.

It will make the load on both
sides in the same direction, which may be more stressful for the
rubber mounts.

IOW, there will be a sideways load on the subframe mounts? That’s
true regardless of anti-roll bar. Perhaps the only valid argument is
that the anti-roll bar will allow the car to corner better, which may
encourage the driver to stress the car more.

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Kirbert wrote:

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. Any
reduction in flexing of one will cause increased flexing of the other.

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.

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. 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.

Gordan

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