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I have a problem with the rear suspension on my 1996 Jaguar XJS with the AJ16 engine.
The drivers side is about an inch lower than the passengers side.
I have replaced the shocks and springs with an overall increase in height (the rear wheel arch used to the 26.5” off the ground, now it’s 27”. The drivers side is 26”.), but still the same problem. I may have saved a 1/2” from what I had before. (I think the old suspension had 25” on the drivers rear, and 26.5” at the passengers side)
Now that shock and springs have been eliminated, what else can cause something like this at the rear suspension?
I replaced those vee mounts with OEM parts about a year or two ago. They look ok. I spent a good amount of time checking out whether they were installed any differently on one side or the other. They appear fine and in no apparent danger of collapsing.
I got my springs from Welsh. They are apparently made in the UK. I desperately tried to avoid Eurospare springs which seem to be very common.
Vee
I think that half the XJSs out there are like that, mine was. Buy a couple of platform adjustable shocks and put them both on the lower side and level that side up using the adjustment. Such shocks are all stiffness adjustable as well, so it is easy to get them balanced with the non-adjustable side.
In my view, this is a sign that the owner is getting the car right. To begin with it is starting problems, cooling, suspension rubber, steering, ignition, fuel leaks etc etc. Then when all done, we start being more picky about perfections! It is me I am describing here!
I tend to agree with some of the previous comments. As you'll know, there are a number of factors that can affect the ride height of one side of the rear of the XJS from cage alignment and mount, through to even the front suspension suspension settings. And even the relatively handbuilt nature of the shell (compared to modern cars) will also influence it.
Although the Jaguar manual states that the ride height for late XJSs is measured from the bottom of the rear cage, I think the only critical element is the visual alignment of the tyre top in relation to the wheelarch lip. So for a comparison of left to right sides, I would tend to measure from hub centre to wheelarch lip, which will also slightly mitigate the impact of a differing camber angle that you may have on the drivers ide?.
Some years ago, my convertible was slightly sagging on the drivers side which I put down to constantly carrying more weight on that side. When I refurbed the rear end, I fitted Gaz shocks and Eibach springs which resolved the side to side discrepancy but the car rode a fraction low. So I then changed to the new Gaz adjustable platform height shocks. And got the height and ride characteristic set up as I wanted.
Greg's suggestion of changing just the drivers side for adjustable height platforms might work, but I wonder if you'll get inconsistent ride characteristics as the drivers springs will be tensioned slightly differently to the passenger side? I think you'd be better off doing what a number of us have done and fitting 4 height-adjusatable platforms then you can set height and ride to suit you perfectly and then you can forget the vagaries of the car structure and aftermarket springs. You might also benefit from a full 4-wheel alignment check on a Hunter bed or similar?
Thank you for the responses. I went through my repair log and discovered that those rear vee mounts were replaced FIVE years and about 50,000 miles ago.
I just measured all four wheel wells. They are very consistent. 26-1/8” on both drivers side and 27” on both passengers wheels, front and back. That eliminates a problem with the rear specifically, and probably suggests that you are right, as Greg often tends to be, and that it may be a characteristic of the car.
Paul, I think you’re recommendation is probably the best solution to this problem. I had the car stolen with the front wrecked. I did have the car at a body shop to make sure the body was straight when I decided to fix it, after discovering a parts car not too far from me, where the seller undervalued the pieces I needed, making the restoration a worthwhile endeavor.
If it bothers me enough, I will head down the adjustable path, but for now, with almost all suspension and parts replaced over the past few years (excluding those front springs), I will see how the car rides, and hopefully enjoy it without spending more weekends in my driveway! (Who am I kidding?)
Keesh, thanks for those dimensions, I’ll get a measurement to share from my car when the weather turns.
Vee, if the spirit is willing and you don't mind many hours of labor, adding/subtracting the spring spacers would probably level-out the car or at least improve the situation. At least the cost of the parts would be negligible.
You are correct. I will probably acquire these spacers, so that I have them on hand when I decide to do this one weekend.
I recall reading that one spacer adds 0.375” to the height, so it appears that two of them at each spring location will get me there.
The rears are certainly doable, but I’ll have to wait until I’m ready to tackle the front spring to do this.
The only other suspension part I haven’t done is the lower control arm bushing. Replacing the spring doesn’t present a “do it since you’re already there” opportunity, does it?
Paul
I do agree with much of what you say; but as far as levelling side-to-side ride height goes, adjustable ride-height shockers all round are no different from a standard ride-height unadjustable set one side, and a height adjustable adjustable set the other, as far as spring-tension differences are concerned! It is just an easier way of achieving Doug's spacer-type adjustment. If it wasn't you would not need the platform adjustables at all. I do recognise that your case, where the ride was level but too low, is different. The shocks bump/rebound characteristics may well be different, but this,if detectable at all, is easily equalised by the bump/rebound adjusters on the height adjustable set.
On my car, to get the rear ride height level, i have Gaz adjustables (not height adjustables) one side, and AVO height and bump/rebound adjustables the other, and the car has never handled or ridden better! Similarly, the front has a different number packing shims each side to get a level height too!
As you correctly hinted, these cars never came out of Pressed Steel Fisher dead straight!
Last edited by Greg in France; 03-28-2021 at 09:53 AM.
You are correct. I will probably acquire these spacers, so that I have them on hand when I decide to do this one weekend.
I recall reading that one spacer adds 0.375” to the height, so it appears that two of them at each spring location will get me there.
Right.
Or, depending on what's already there, it might be a matter of removing spacers from the high side as well.
The rears are certainly doable, but I’ll have to wait until I’m ready to tackle the front spring to do this.
The only other suspension part I haven’t done is the lower control arm bushing. Replacing the spring doesn’t present a “do it since you’re already there” opportunity, does it?
Not really, no.
Lower bushings are real work. Removing the springs, although itself a bit of a chore, is the easy part. The real problem is the big bolt/shaft that runs fore-aft through the control arm. Firstly, it is often seized in place...which means tons of hammering. Or, sometimes, cutting it off. Second, these shafts are driven out to the rear and there's no place for them to go unless you drop the steering rack out of position or drop the front subframe.
How bad are your lower bushings? If they're totally shot, well, it might be contributing to your ride height problem. If still serviceable, you could correct your ride height problem and replace the bushings down the road.
Paul
I do agree with much of what you say; but as far as levelling side-to-side ride height goes, adjustable ride-height shockers all round are no different from a standard ride-height unadjustable set one side, and a height adjustable adjustable set the other, as far as spring-tension differences are concerned!
One of the problems with ride height setting is deciding which height to use. It could be, at least one of these three:
Height of the diff centre plate above the ground
Height of the cage each end above the ground
Height of the wheelarch above the ground
In my case I measure from the ground up to the wheelarch rim directly above the wheel centre, as it annoys me if the gaps to the tyres are too large or not the same each side, and I try to get each side to within 1/2 an inch. So what can affect this? Spring rates being slightly different, cage mounts not the same (though I have never seen this on anything but a scrap-worthy car), shock absorbers being just slightly different in length outside of the spring-holding section, chassis rails to which the cage mounts are bolted not being 100% level with each other, and as the car is rigid, any ride height differences at the front suspension will affect the attitude at the rear, as a car must stand on at least 3 of its four paws!
Now as to handling, and talking of the rear only at this point, as long as the subframe is straight, and the springs and shock absorbers the same each side (ie the subframe and suspension are sitting level and are dynamically identical each side), it matters not a jot as far as the car's handling is concerned that one wheelarch is an inch higher off the ground than the other! The suspension does not know that the body appearance is not quite level or that the chassis rails are not 100% identical in position, or that even the rear wheelarches are not quite the same level, any more than it knows that it has been removed from a Jaguar and bolted into a Cobra replica!
Now I am not saying that the height of the body does not matter, jack it up too high and the centre of gravity changes handling dramatically. Nor am I saying that fitting a too strong set of springs, or shock absorbers which are too long, both of which will raise the ride height of the cage itself even if the same both sides, does not matter. The cornering ability and roll will most certainly be affected.
What I am saying is that assuming all as OEM in springs, shocks, cage mounts, etc, once the cage is bolted to the car, the ride height as it affects handling will be fine. But in many cases the gaps to the wheelarches may NOT be the same.
I therefore believe that in common with me, in most cases it is really an appearance matter that makes us want to adjust the ride height so that the car presents a balanced appearance and the desired stance front to back.
Why wouldn't you measure the ground to the cage ends first.
If that is right, then measure ground to wheel center and then to wheel arch.
After you establish that all that is correct, you at least have narrowed things down.
Making adjustments and shimming things before you know what is wrong only addresses appearance.
You might have a bent frame, damaged mounts or any number of defects that won't get addressed.
I've taken measurements from the center of the bolt holding the rear shocks in place. (no front shock readings are taken here)
The readings are not equal!
On the drivers side, the center of the front bolt holding the front shock in place is 7.25" from the ground. The center of the rear bolt holding the rear shock is .25" higher.
On the passengers side, the center of the front bolt holding the front shock in place is 7-1/2" from the ground. The center of the rear bolt holding the rear shock is 0.5" higher!
The bottom of the bolt head at the rear x-brace also has a 1/2" difference, and they match the center of the rear bolt at the rear shock.
When this car was stolen, the front was damaged. The repair was all sorted, making sure the body and frame was still straight.
What I never really paid attention to was the fact that the car was towed from the back. It appears they had wrapped a strap around the rear passenger axle.
Now a four wheel alignment did not reveal any issues. (Even though I know rear wheels cannot be adjusted, I paid for the four wheel alignment to get the numbers)
The only part I still see a reminder of what happened was a slight distorted “rear IRS tie”, or part number CAC2416. Can this part affect the suspension height?
The only part I still see a reminder of what happened was a slight distorted “rear IRS tie”, or part number CAC2416. Can this part affect the suspension height?
No, it cannot. Vee, those numbers are 100% fine. You will never find 4 springs, even brand new, that have exactly the same compression under load. You do not know, without corner weighting the car - which is just about impossible on the XJS rears as the shocks cannot be disconnected and the car stay upright - just what weight is on each side of the axle. You cannot remove all "sticktion" from the at-rest suspension. You cannot know what load the front suspension is supporting each side either, and this affects the rear axle too.
So I say ensure you have half a degree of negative camber all round, and drive the wheels off it!
I understand I don’t have to do anything now, thank you,
however,,,,
If I did add two shims for each drivers side spring at the rear, and the front, would the body appear level, or am I just going down a complicated path?
03-27-2021, 04:43 PM
Facelift - Rear Suspension Low on One Side
