XJ6 & XJ12 Series I, II & III 1968-1992

Anti-Roll/Sway Bar Upgrade/Addition

 
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Old 10-30-2014, 07:42 AM
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Default Anti-Roll/Sway Bar Upgrade/Addition

Has anybody added a rear sway bar to their XJ6?. Any pictures as to how they are installed. I ran across a Jag site last night touting better roll control with their larger front (1") bar and the addition of a (7/8") rear sway bar. According to the site, the XJS's with the sportspack suspension option came with front and rear bars. He (SportCat) also lists them for the XJ6, not only the XJS.
Anybody done this to our sedans? I would like to eliminate some of the body roll, realizing that due to the weight of these cars, total elimination is impossible.
 
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Old 10-30-2014, 08:08 AM
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All the XJS front and rear anti-roll bar stuff will work on a Ser I-II-III sedan.

For the rear, after getting all the parts you'll need to drill holes in the floor pan for the "U" brackets. Probably a good idea to reinforce the floor a bit as wheel. (Most XJSs already have the floor/underbody mountings, but the sedans don't)

I would advise against a 7/8" rear bar. That's awfully big. I had a 3/4" or 7/8" rear bar (can't remember now) on my XJS and the results were not satisfactory. The stock size (9/16" or 5/8" ---something like that) worked better overall, and is a better choice IMHO.

You might consider just the 1" front bar. That will reduce body roll quite a bit. You'll get more understeer in very hard corners but that might not be an issue for you, depending on driving style/conditions/agressiveness. I was happy doing so on my Ser III XJ6. I had planned on a rear bar but just never got around to it.

Cheers
DD
 
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Old 10-30-2014, 08:19 AM
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As Doug has said.

Too thick a bar will be bad, unless tracking the beast.

I fitted a standard XJ-S rear bar to one of our S2 Daimlers, and I got the rear bar, drop links, trailing arms, "D" brackets off a PreHE that was upside down in a breaker yard.

I found that our car, a 9/1976 year, actually had the 4 studs sticking out of the floor under the car, behind the muffler insulation, and were definately factory. This is due to us owning it from day1.

That made such a difference to that car, just tightened the whole shooting match, without any harsh effects.

The front bar was as made.
 

Last edited by Grant Francis; 10-30-2014 at 05:33 PM.
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Old 10-30-2014, 09:33 AM
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Thanks for reply Doug.
I was thinking about just doing the 1" bar upfront and see how it goes. You seemed to like it, so I will try to find one.
One thing Doug, don't you mean the addition of a larger front bar will cause oversteer, and not understeer?
Example case. My 73 Vette did not come with a factory rear bar. Only a front. When I decided to add a larger front bar (1" to 1/1/4" in this case) and a rear bar (5/8"), I decided to take the car for a drive before actual installation of the rear bar, only had larger front installed. The car changed from fairly neutral to "tail happy", meaning oversteer. When I finished installation of rear bar, car went back to neutral. My reasoning as to why this happened was with the addition of the larger front only bar, the front end stuck to the pavement better, but the rear did not get the same "treatment", hence the "tail-happiness".
 
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Old 10-30-2014, 09:48 AM
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My subjective, unscientific and possibly useless experience: I've been having a problem where the right side of the front (and only) sway bar on my 88.5 XJ-S keeps coming loose from where it mounts to the body. I know when this has happened not only because I can hear it but because the rear end seems to strongly want to swing out from behind me on turns any faster than 50 mph. With the (stock) front sway bar attached, the car feels neutral and sticks to the road at more gratifying freeway speeds.

In fact, when working properly, my XJ-S handles so well, I can't help but wonder what I can do to improve the handling of my new-to-me series III. I just bought a pair of uprated/poly bush enhanced sway bar end links from V12s.com. They made a big difference at least in the ride of my XJ-S in terms of smoothing out feedback from the road but I can't remember if the body roll improved much. Hoping it will help, even a little on the series III. Having them installed tomorrow. I'll report back, if anyone's interested.
 

Last edited by Rhett; 10-30-2014 at 09:59 AM. Reason: Additional relevance to the thread, hopefully.
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Old 10-30-2014, 11:32 AM
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Originally Posted by Dale Konkol View Post
Thanks for reply Doug.
I was thinking about just doing the 1" bar upfront and see how it goes. You seemed to like it, so I will try to find one.
One thing Doug, don't you mean the addition of a larger front bar will cause oversteer, and not understeer?

No, I meant understeer.

The Jags, like almost all cars, were set up to understeer. Increasing the front bar, without a rear bar, would only make it understeer more.

The older Corvettes were also understeer cars, with or with the rear bar. However, it's very easy to create 'throttle induced oversteer' with them....which I sort suspect is what happened in the example you gave

Cheers
DD
 
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Old 10-30-2014, 11:53 AM
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As always Doug, right.
My mind must be going. I had it backwards as far as the Vette example goes.
Increasing the size of the front bar will (when in turns) cause more of the weight of the car to be shifted to the rear of the car, therefore increasing traction at the rear, and thusly less at the front. I think I got it/remember my Corvette suspension research done some 30 years ago.
That also jives with what Rhett mentioned when his front bar is loose. When loose, more weight is being shifted forward, and because of it, causing oversteer.
Anyway, now to track down a 1" bar.
Thanks for input.
Appreciate it much.
 
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Old 10-30-2014, 12:35 PM
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What I know about tuning suspensions is just enough to confuse me.


But, fundamentaly, the terms are a bit confusing. Roll and sway for example.


Now, roll is a term that can be dealt with. All cars have a roll center. External forces move the unsuspended mass about that center. That movement is load transfer. Too much isn't good, but not enough is an issue as well!!


Now, a "sway" bar ought be termed a roll control bar in my lexicon. In mechanical terms, it is a torsion spring. Same as a coil spring.


However, it is neutral when the car goes straight. But, on application of force via a turn, it transfers load as it twists.


Ie, hard left turn. The right front wheel bears load. it needs to maintain traction.
Slick, except what about the left rear? It will raise and break traction. result, a one legged car or none if the diff is open!!


Yeah, roll control can be achieved via stiff springs. But, the load is constant, unlike roll control bars. neutral when not needed.


OTH, if the roll control bar is too stiff, It may remain rigid and absorb no load. Merely make the front suspension no longer independent.


Result, a go cart!!! And, that can work?????


Carl
 
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Old 08-06-2017, 01:08 AM
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Thought I'd fire up this old thread as I wanted to know a bit more about this. In particular where I need to drill holes for brackets etc.

I did find some pictures on Jag Lovers, but they don't really help too much.

If someone has some better pictures, dimensions or drawings of a Rear Anti Roll Bar fitted to an XJ6, that would be great.
 
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Old 08-06-2017, 01:21 AM
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On all my S2 cars, the studs were already there, just hidden behind the exhaust heat shield fibro stuff.

The XJS, '85, also had the studs installed from the factory.

No idea on the S1 cars though, but I really had to look for them, they were NOT in your face, as we say.
 
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Old 08-06-2017, 08:10 AM
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Originally Posted by Grant Francis View Post
On all my S2 cars, the studs were already there, just hidden behind the exhaust heat shield fibro stuff.

The XJS, '85, also had the studs installed from the factory.

No idea on the S1 cars though, but I really had to look for them, they were NOT in your face, as we say.
The reason I ask, is that my rear suspension is off the car at the moment and if I need to do some welding, now's the time.
 
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Old 08-06-2017, 09:03 AM
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Go to post #4 of this thread for a couple pics that might help



https://www.jaguarforums.com/forum/x...tinued-177670/

Cheers
DD
 
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Old 08-07-2017, 05:41 AM
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Originally Posted by Doug View Post
Go to post #4 of this thread for a couple pics that might help



https://www.jaguarforums.com/forum/x...tinued-177670/

Cheers
DD
Thanks Doug, they do help.
 
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Old 08-09-2017, 06:37 PM
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Originally Posted by Dale Konkol View Post
As always Doug, right.
My mind must be going. I had it backwards as far as the Vette example goes.
Increasing the size of the front bar will (when in turns) cause more of the weight of the car to be shifted to the rear of the car, therefore increasing traction at the rear, and thusly less at the front. I think I got it/remember my Corvette suspension research done some 30 years ago.
That also jives with what Rhett mentioned when his front bar is loose. When loose, more weight is being shifted forward, and because of it, causing oversteer.
Anyway, now to track down a 1" bar.
Thanks for input.
Appreciate it much.
.

pic of my 1" front antisway bar.
truth is it seems to increase sway in the rear end, no rear bar tho.

i suppose with more torque ,it would make a great drift car, the V12 torque comes on slowly ,NOT good for drifting.
 
Attached Thumbnails Anti-Roll/Sway Bar Upgrade/Addition-r1-07368-013a.jpg  

Last edited by ronbros; 08-09-2017 at 06:40 PM.
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Old 08-13-2017, 01:39 PM
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ADDCO sway bars and bushings.
 
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Old 08-13-2017, 01:46 PM
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I tried to order one a while back... but they had a long back order... Have a stock front one but would install a small OD rear bar.
 
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Old 08-22-2017, 05:13 PM
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better pic of 1jnch antiroll bar.

remote trans oil cooler , i dont run any hot oil thru thru radiator.

pix upside down cant get it upright?
 
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Last edited by ronbros; 08-22-2017 at 05:18 PM.
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Old 02-03-2019, 03:54 AM
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Okay, so while I haven't yet acquired a Rear Anti-Roll (Sway) Bar yet, I have started on work to provide the provisions for it! I have contacted a few companies in the States, but they were reluctant to give away too much info. I tried Harvey Bailey Engineering (HBE) and they were kind enough to provide instructions for their kit. I won't post them here until I received permission to do so. I have a Series 1 car and there are no provisions as standard. To this end I have prepared the are in which the brackets will fit and will make my own brackets in the next few days. Once I'm happy with the brackets, I will use them as a template to drill into the car.

I also got some great info from this thread in the XJS forum: https://www.jaguarforums.com/forum/x...ay-bars-72502/

I have removed the wax protection in the area of the car where I intend to fit the brackets based on the information supplied by HBE. I have marked the centre-line of each bracket and used some thin steel to get the rough shape. This will info my final bracket design. Here's a few pics for reference:



The wax removed above the propshaft is due to heavy grease contamination after the UJ started to wear. I replaced the UJ but never fixed the wax protection.


Is the underside of the S2/3 cars diffferent to my (all) S1 cars? DO they all have the seam running across the car between the chassis rails? I know that XJS' don't have that seam, at least not in the same location.

More to follow as I have it.
 
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Old 02-06-2019, 05:45 AM
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So I finalized my bracket design after several checks and measurements and now have the provisions for a Rear ARB! I still need to make a load spreader bracket for the inside, but really happy with how they turned out, despite some dubious TIG welds on my part!







These are the bolt heads inside the car under the rear seat:







Hopefully these will be of use to someone thinking of the same.
 
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Old 02-06-2019, 06:53 AM
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Nice work - Congratulations. Correct about the load spreader plate. I would fabricate a plate that not only picks up on the two existing bolts, but is large enough (kind of squarish) so that two more bolts fasten the plate itself to the sheet metal. If the two existing bolts are at 12 and 6 o'clock, the other two would be at 3 and 9 o'clock. That bar will exert a lot of force during "spirited" cornering.
 
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