Hello my fellow XJS owners, iv'e been battling this issue for years and can't seem to solve the problem and i want to know if anyone else is having the same or similar issue with their XJS. Little background on my car, it's a 1986 Jaguar XJS (was V12) now V8 LS3 T56 cammed tire smoking monster, i have 19 inch wheels on it all the way around with 9.5 inch wide up front and 10.5 inch wide in the back. The ride height is altered so its little low up front but not too low. Now my problem, the car wonders on the road like something is loose in the steering system, i have brand new bushings and mounts all around the car, subframe, rack and pinion, rear cage with radius arms, everything is new, new bearings rear and front wheel hubs, no up and down play at the front wheels but almost not noticeable in the rear, so i don't know why the car still wonders, the alignment is perfect on it too. I even upgraded the rack and pinion to 93 and up slimmer and better one, still does it, on perfect road it's fine but as soon as road condition changes, car wonders around. I hope someone can help me fix this issue or try and any help is greatly appreciated. And if you guys need any more info about the car, just ask, i have 4 QA1 adjustable coilovers in the rear and 2 regular shocks but rebound adjustable up front.

 

Given all the possibilities you've eliminated I'd thinking you may be experiencing tramlining.

How does the car drive with narrower, higher-profile tires?

Also, what is your caster set at? Lack of positive caster can give a wandering feel; more positive caster gives a strong 'on center' feel

Cheers
DD

 

I'm with Doug here.

Whell alignment setting up is an art, and if not done in the correct procedure will bite ya.

Balljoints getting stiff always causes wandering on a standard car snd they are vey hard to detect without weight on them, which of course is the car.

If they are the original jooints, waaaaay past use by date in any market.

 

thanks Francis and Doug, i think the caster is set to 3.5 degree positive both sides, it did this same thing with Corvette C5 wheels 17 in the front and 18 in the rear, my ball joints are new. Should one side have more positive caster than other? or both same? i always did both same and all the shims but it helped a little, not all the way. i'll mess with the caster some more and see what happens.

 

Doug you might be absolutely right, tramlining might be my problem, because this started happening when i went with bigger wider wheels with way different offsets than the stock wheels. sadly i can't put the original wheels on, to see if it'll correct the problem because i did a big brake upgrade with C6 Z06 14'' rotors and S Type R calipers so smallest wheel i can put on i thing is 17''

 

There ya go.

Not every car I've driven with wide, low profile tires tramlines. But I've car I've driven that tramlined had wide, low profile tires. By low profile I mean, oh, less than 50-55 aspect ratio.

There are lots of variables to tramlining. Different suspensions/cars react differently to very wide, low aspect ratio tires. And the tires themselves can make a difference....different construction, sidewall design, tread design, etc..... so you might try different tires.

My XJR tramlined a lot ...sometimes in a scary way....with 255/45x17 tires but not at all with 235/55x17 tires


Cheers
DD

 

my tire size is 235/30/19 up front and 275/35/19 rear, way to narrow for the front wheel, i gotta change it to 265/45/19 in the front and gonna try to put 285/45 in the rear, i don't know if it'll make it worse by going wider but i have too, i looks stretched now with this tires. Thanks for your guys's help. i'll try to change the tires soon and update the thread. Happy Easter

 

I was having this conversation with a friend of mine 2 weeks ago, he is retired now but used to build E Type and XJS race cars.

My car pulls to the left and I have been through everything and can not find ant issue. Although the roads around here are very rutted due to the large number of trucks. Norm was telling me he has Corvette 16x8.5 on the front of his XJS and to run the pressures a little higher. He suggested 32-34psi as a starting point, and less camber around 0.5°.

265's on the front, you will almost certainly have rubbing problems on the inner components. My 245's rub ever so slightly on the sway bar at full lock.

 

Thank you Warrjon, actually with this wheels i'm more convinced it'll rub on the fender on hard cornering than the inner part due to my offset but i can fix that by giving little more camber and adjusting the stiffness of my shocks. i guess i just have to suck it up and live with it if i want to keep these wheels, it's not too terrible now with this new rack and pinion from a newer jag, it was way worse with the original one but i'll still try different things and suggestions to either eliminate the problem or minimize it as much as possible.

 

I agree, tramlining is the main suspect. Tyr a quite a bit more negative camber and more toe in. But fundamentally, the suspension is not designed to control tyres that wide without considerable camber, castor and toe adjustments from factory spec. The racing guys in the UK may well be able to suggest some settings, give the JEC racing chief an email.
Greg

 

I had to chuckle. The car "wonders". Same as wander? YUP, it can't decide where to go.
Apologies, I love word play....


Yes, suspension geometry and wheel & tire size and offsets often clash. Been there a bit with 4x4's. One or two issues eased by adding "stabalizers" to the steering linkage. Just dampeners.


A way to visualize is to make some drawings. Factory vs now. How far off is the vertical line drawn from center to center of each tire/wheel to he center of the "up right". Aka "king pin" in old tech.


Now, think inertia control over the big wheels and tires over the originals. Flex translates to steering input. Voila tramlining!!!!




Carl

 

I think JC has hit the nail on the head.

Wider front wheels (more than 7") on the XJS require a large offset change which moves the centre line of the tyre contact patch outwards increasing positive scrub. Increased positive scrub will have a tendency to make the tramline.

When I replaced my wheels I went with close to TRW spec 20mm offset for the front compared to 28.5mm for the stock wheel. I also run 1.2° negative camber.

Both of these changes have made a significant improvement in the response of the steering but the trade off is less straight line stability. My car is probably not just pulling left but following the camber in the road.

Increasing negative camber will make your tramlining worse.

To reduce tramlining - reduce negative camber and increase toe-in. You'll have to experiment with what works for your wheel/tyre package

 

Thanks JagCad and Warrjon, i will try a little more toe in and see how it goes. I appreciate your help.

 

I ran a particular brand of tyres on my range rover at one stage (toyos from memory, 18 inch wheels) and it tramlined to such an extent it was dangerous. Changed to a different brand/design but exact same size and problem disappeared.

 

Thank you Baxtor, i will keep that in mind, that's a good point.

 

I tried a little toe out on My Racing solo II (autocross) sprite.. it was so twitchy and faster to respond (sprites are from the go) I set it back to a little toe in... seem like a good idea at the time... (NOT!) ran only one event that way...

 

Another thing that can cause tramlining is excessive play in the rear wheel bearings. This causes the rear to steer.

 

Good point. Camber change !

Also, badly worn output shaft bearings in the diff can do the same. On my '88 XJS there was enough free play in the output shafts to significantly change rear wheel camber....a little spooky at times !

Same, too, for the lower control arm bearings

Cheers
DD

 

did you have a look at the rack mounts?


https://shop.advanceautoparts.com/p/...=steering+rack

 

As I mentioned earlier my car was wandering/tramlining badly on our uneven roads here in the bush.

When I originally put the front and rear back together I was running stock 215 656 15 tyres I had no issues with tramlining and set the camber 1.0° front and rear, when I changed to 245 50 16 all round the car began to tramline but was not noticeable on the good interstate highways.

The other day I re-aligned the car and dropped camber back to 0.5° front and rear, this significantly improved the wandering and for the most part the car now tracks much better, although it still wants to follow the deep ruts and road camber does not have the car wanting to head off into the scenery.