This video is an interview with Norman Dewis, where he describes why the early XJS has a skinny rear rollbar that was later deleted. Dewis was Jaguars chief test driver, and was the guy who wrecked the XJ13! He only recently passed away.
ā¦later reintroduced, and re-deleted, and reintroduced!
This enjoyable historic tidbit has come up elsewhere.
Not to disparage old Normanās opinion but he seemingly missed a generally well-accepted realization: what works best, or feels best, on the race track isnāt always what works best or feels best for street driving.
Cheers
DD
In about 99% of the cases.
Had a helluva time trying to convince customers of that.
Yep. I added that skinny rear anti-sway bar to the rear of my '83, and simply loved the effect it had. It made the car feel planted, more stable, more responsive to steering inputs. But how it feels doesnāt necessarily translate to being faster around a road course, and it is added weight.
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TWR stiffened the shocks and springs and deleted the rear anti-roll bar on my XJR-S. On my Alfa Spider I fitted the Alfaholics Spec B suspension kit which stiffened the rear end and they also said to remove the anti-roll bar. There must be something in it?
Every chassis is going to handle differently, at its limits, and in response to the driversā needs, at any given point on a track.
Por ejemplo, my 1200 Datsun racer was capable of all thee basic handling envelopesāunder-, over-, and neutral steerāw/o needing a real ARB.
I wore out 3 sets of tires in testing to determine that. For all but a short road course and auto crossing, it worked perfectly with the rear ARB disconnected.
Otherwise, I just disconnected one link. I left it place because I needed the extra weight, to make minimum weight, and to put that weight rearwards.
Hi,
I talked with him (ND) about the same concerning the V12 E-types (no rear sway bar). He said āit was better without one.ā And I have found nothing wrong with the handling of our unrestored OTS #1S20183.
Also a couple of experienced Finnish racing drivers told me, that in their opinion a rear sway bar is (quote) āa futile attempt to fix other problems in the chassis and suspension.ā 
It can be, but not necessarily.
Most hi-perf cars have them: in most regards, rear ARBs are a ātrim tabā, rather than a crude fix.
For decades now Iāve been adding a rear bar to almost every car Iāve owned that didnāt already have one, including my Jags. In each case it could be said that the car didnāt āneedā the rear bar. And in each case Iāve been pleased with the improvement. 
Cheers
DD
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Thatās a good way of putting it, Iād say
I have to chuckle a bit. This subject (rear ARBs) comes up every year or so. There are always some who have installed a rear bar and are glad they did. And there are always some who havenāt installed one and who come up with reasons not to install one.
Iāll I can say is āDonāt knock it 'till youāve tried it!ā 
Cheers
DD
Datsun Competition had this wee small manual, that came with the blueprints for modifying my 1200 Datsun. I have never read a more incisive and accurate description of how one needs to deal with a race car, in a highly dynamic situation.
In short, it very nicely said, in a kind way, damn few drivers know HTF or WTF to do with a car, to benefit its ultimate handling envelope.
Iāll try to find it: I posted it on the old forum, but thatās been 12-14 years ago. Itās around in my papers, somewhere.
EDIT: the new search engine DOES workā¦ I found it!!!
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An anti-roll bar is, in essence, just another way of stiffening the suspension. If the suspension is stiffened by other means (spring and shocks, as you mention) the ARB becomes redundant or possibly counter-productive
Cheers
DD
I certainly donāt.
āUltimateā and āmaximumā of anything car-related is beyond meā¦ on multiple levels and for various reasons. I enjoy ābriskā driving regularly and, when opportunity permits, will become mildly aggressive. Thatās about it for me ! My wild-man-with-his-hair-on-fire days are a distant memory. This might be why Iāve always like a rear ARB and the comp/track guys donāt. Two different worlds.
Cheers
DD
Thatās it, exactly
Cheers
DD
Absolutely trueā¦
Naaaaawt really: in a simplistic way, yes, but the relationship between front roll rate and rear roll rate (āroll coupleā) plus the effect of the mass centroid axis upon that, andā¦well, yeah!
Z bars, however, are indeed essentially just an added spring.
In the end, Iām pretty sure olā Normie knew what he was doing.
Simplistic is the only way I know
No doubt!
And, actually, my experience agrees with his in one sense. Having tried two (or maybe 3? Foggy memory) different rear ARBs on my XJS I can attest the too-big is a bad thing.
Jaguar used two sizes on the rear of the XJS; the difference was slight; maybe 1/16th inch. I canāt remember which I had, but they were significantly smaller than the aftermarket one I triedā¦which was too much.
Cheers
DD
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Hi,
Of course I have driven over 40 thousand miles with a LWB E-type with the rear sway bar, and a few times on track etc. With standard size tires there is no reason why I would want to add one to the V12 E-type OTS. yes, I have tried many different setups and most of the āperformanceā upgrades fellow club members have had in their E-type have been IMHO to quote Monty Python āa complete waste of timeā. 
BUT this is the XJS forum and the original message was about the rear sway bar on an XJS on which have no experience whatsoever. Of course I have driven many XJSās,. both coupĆ© and convertibles, bu I have no idea if they had a rear sway bar or not as they were not my cars.
The only reason why I decided to join on in this conversation was my initial surprise when having owned the V12 E-type for almost a year I realized it did NOT have a rear sway bar. :-o
At first I though some DPO had removed it, as the body and rear axle had the mounts for one, but then I found out that it was the factory that left it out. Too bad they did not tell the body shop they did not need to weld the brackets to the 15.000 Series 3 E-type bodies madeā¦
I was also quite sure it was how the car was made, as on mine the plastic plugs they put in the tapped bolt holes before the car goes into the paint shop at Browns Ln. were still there.
Cheers!
Hi Pekka,
First Iāll say that my remarks were not intended to call into question anyone elseās knowledge or discount their own experiences.
My view on the matter is that the Jaguar guys, as with any manufacturer, make decisions that they consider ābestā in the grand scheme of things but which might not be best for, suit the tastes of, every owner or driver. Sometimes I sense a notion of āJaguar knows whatās best for everyone. Jaguar didnāt install it, therefore I canāt benefit from itā.
Iām merely trying to dispel that notion
Cheers
DD
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Hereās the thing: Lotsa people think size is absolute, if you like a 3/4" anti-sway bar on the back of one car youād like that size on the back of all cars. But there are differences in the way anti-sway bars are connected, not to mention the suspension designs they are connected to, that cause differences in the size bars needed. The rear anti-sway bar for the XJ-S is 1/2" which would be considered tiny for most cars but itās plenty here. The aftermarket bar available was waaay too much, possibly because their customer base insisted on a big strong one.
Unique to the XJ suspension, a rear anti-sway bar operates through the small end bushings on the trailing arms. So the soft-as-hell OEM bushings absorb much of its action. Replace those bushings with stiffer, or even poly, and your rear anti-sway bar will be far more effective.
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