Suspension misalignment

[JCS]

John

Adjustment of packing rings on both front and rear suspension is possible on classic S type cars. In both cases the adjustment is as near as matters 2 to 1. That is a packer 0.250 inch thick will raise the ride height 0.500 inch. All things being equal, the body standing height dictates the angles of the top and bottom suspension arms, particularly critical if rack and pinion steering is fitted.

Firstly it is necessary to establish the current ride height, with full fuel tanks and correct tyres and pressures. I find the acceptable way to clone the factory build position is to attach masking tape, lined up along the gap formed by the front and rear doors and cill. The extension of this tape at the rear end forms a tangent with the top of the circular section of the spinner. At the front, an extension of the tape passes approximately through the centre of the front spinner. This position matches the Jaguar dimensions for the body shell and images in brochures, it also produces correct front and rear lower suspension arm angles.

One problem that I often see on these cars is that they are front end high and fitted with Jaguar Mk 2 front springs. These springs have a wire diameter of 0.635 inch but the S type had 0.610 wire. Although, having said that, I have measured some front springs with an intermediate wire diameter and it is possible Jaguar suffered problems matching spring poundage’s. They would not be the first maker to have special springs on one side ready to adjust the ride height of an odd chassis.

In the case of rear spring packers, these are at the lower end of the springs and the standard today seems to be alloy 12 mm thick and I know 4 mm or so have been fitted. These alternatives possibly originate from other IRS Jaguar suspensions. I think the limit is around 15 mm thick and beyond that there is a risk of spring displacement, however that might be counteracted by manufacturing (steel) spacers in a deep top hat shape. Certainly SNG stock the 12mm alloy spacer because I have used them on my own car.

[Glyn Ruck]

John from what I have read and Glyn might be able to back me up on this but those packing rings for the front suspension where factory fitted for another strange reason.
Not as you think to raise the front ride height evenly per say but they were fitted depending on whether your car was right or left hand drive. The packing rings were placed on top of the spring on the driver's side to compensate for the drivers weight in the car. They assumed that 90% of the time the car would be driven with no passengers so the spacer jacked up the drivers side slightly so when he got in the car sat level.
I removed my spacers from the springs when I did my rebuild. I had two but I could not remember which side they came off and did not know about this drivers side thing at the time so took them out. I still have them in a box in the garage somewhere. I think I had two different sizes so perhaps one 1/4 and one 1/8 inch.
Raising the springs using spacers under the spring tops can be done and could be used to adjust the ride height but the only way to drop the height is to get shorter springs which is what I did eventually.

Strange as well Glyn that all those brochure photos are of steel wheeled cars!

Yes ~ no wire wheels in brochures until 420 US brochures as all US 420's were fitted standard with wires. Sovereign was not sold in US.

I refitted my original springs after sending them to a local spring works for resetting spring rate to original spec which they still had & then powder coated them.

Firstly the factory matched up spring sets for what model they were to be fitted to with paint like this. Blue, Yellow, Red etc.

DSC00013.JPG (30.93 KiB) Viewed 1941 times

Then the factory matched up spring sets for equivalent spring rate etc. They should be colour matched on both sides of the car. See the rest on this colour coding on the centre coil in the below snip. (Sometimes require to remove covering tape if still present.)


Coil spring packing pieces ~ front:

Coil spring packing pieces front.JPG (74.94 KiB) Viewed 1941 times

No such data is provided for the rear spring packing pieces. It is suggested that only red & yellow were used to identify rear springs. The above pic proves this wrong. Maybe corrected in a later manual. JCS has however covered partially above.


Rear springs:

Coil spring rear.JPG (23.09 KiB) Viewed 1941 times

Packing pieces from what I've read regarding LHD vs. RHD are to accommodate typical loading, manufacturing variances & camber of the road. This does not quite gel with what Jaguar says above as regards camber of the road.

Some detail scribes use is just plain wrong and other gleaned from interviews with the likes of Crouch.

[jaguar&mg]

Thank you for all of the help and advice. It matters to me so I shall investigate the possibility of wrong springs and/or packing rings.

Here's the pre-new-springs pic — should have left well alone!

Jag.jpg (82.5 KiB) Viewed 1909 times

[Glyn Ruck]

You are the one that has to be happy. Good luck! Yes it looks pretty good as it was.

Looks like you are running Michelin tyres ~ good choice.

Lovely car BTW.

[JCS]

Cass

You mention in one of your replies that at one time you were not aware of the reason for spring packer rings. Only later were you advised, or read, that front end packers were fitted to “compensate for the drivers weight”

I have read and gathered extensive data on vehicle springs, from a number of archives and sources and I am particularly interested in the source of the information you quoted.

Can you advise, where the data connecting spring packers and drivers weight arose, and did you question that comment?

Norman

[cass3958]

Norman I did mention it and I am sure I read it somewhere but I could not tell you where. I will have a browse through my books and magazines tomorrow and see if I can locate it for you. It might also have been something I read off the internet and you cannot always rely on it being correct.

[John Quilter]

JCS comment:

the body standing height dictates the angles of the top and bottom suspension arms, particularly critical if rack and pinion steering is fitted.

Since my S Type runs a rack & pinion, I am particularly interested in this comment. Can you expand on it giving the technical reason for this?

John F. Quilter
Eugene, Oregon USA

[JCS]

John
I am sure that you understand that alterations in body standing height will alter road wheel track. For the benefit of those who do not understand, the following example may help.

If the car is raised by jacking on the centre of the front sub-frame beam, the front wheels will move towards the centre of the car. In short the front wheel track will alter and narrow, and the wheel positive camber will increase.

Therefore if the body height, and therefore the suspension height and wheel camber increases above the desired ½ +/- ½ positive camber, the tyre contact patch may well reach an undesirable position. If this loss of tyre contact occurs during hard cornering a dangerous situation could occur as tyres lose grip.

In the case of rack and pinion steering I think it is sensible to reduce the bump height by a further one inch to prevent suspension movement leading to a dangerous situation. I will shortly be carrying out this exercise on my own car and I know a much respected Jaguar specialist who always carries out this modification on rack and pinion cars.

The max Jaguar front suspension movement is around seven inches (I have not checked). This is normal for cars of the period, however the normal working band is only one inch up and one inch down, two inch total. The design ideal is to position the lower suspension arm so that the working radius is within this two inch to prevent major wheel track alterations. Naturally, when the wheel track alters under dynamic conditions, so does castor, camber and tracking.

Examination of the front suspension (and rear suspension) in the workshop manual shows the static arm positions.

In the original steering layout the radius of movement of the inner tie rod joint was designed to shadow as close as possible the radius of movement of a line drawn between top and bottom inner suspension joints. This, to maintain steering accuracy throughout suspension movement.

In the case of current rack and pinion steering conversions the length of the rack body and tie rod operating radius, make close shadowing of the suspension arms impossible. The steering geometry in that case means that correct toe out on turns is not possible, but can be improved by statically setting the steering track just at the zero to toe out position.

Although most of the above discussion centres on steering and suspension angles, the object is to show how incorrect suspension (body heights) affect suspension and steering angles.

If you have incorrect standing heights you have incorrect steering and suspension angles, and if you add rack and pinion steering it gets worse. This is not to imply steering conversions are no good but merely to suggest extra care on suspension / body heights.

I have R&P steering and no desire to change.

I tried to keep it as simple as possible and I hope it is understandable.

Norman

[Glyn Ruck]

I guess it would also mess with the Ackermann angles which can be difficult enough to get right with rack & pinion conversions.

[jaguar&mg]

John

If you have incorrect standing heights you have incorrect steering and suspension angles, and if you add rack and pinion steering it gets worse. This is not to imply steering conversions are no good but merely to suggest extra care on suspension / body heights.

I have R&P steering and no desire to change.

I tried to keep it as simple as possible and I hope it is understandable.

Norman

I think this may be my problem. Not only are the springs quite new, but there was also a R&P conversion three years ago for power-steering installation.

A further indication that this is the cause, perhaps, is that there is some [new] 'wallowing' going on above 60mph. Putting more air in the front tyres has helped the road-holding a great deal, but it can still suddenly be alarming if there's a dip in the road — recovery includes use of the brakes!

Perhaps this is an issue more than just of appearance.