OK, now with 6500 miles under my tread, and 16 on the 07, I've some observations. What started as a steering judder in the wheel at low/idle speeds has resolved but at fast/hard cornering, gas returned into an unnerving judder in the wheel when tossed into a turn. the car responds beautifully for what it is but the wheel judder feel like our old 1968 Dodge van.

And how many S's were made sans air suspension? Mine is straight coils and, it may be the wobbly Michelins from sitting for 18 months, my low miler sure has a 'every ripple in the road' feel to the suspension, through the seat of the pants. Even my old hot rod forester seems to have a smoother ride on a smooth surface-tire factor? Every air sprung Jag I've driven was silky smooth.

Maybe I'll leave the bevy at just two for now..! Any insights appreciated.

 

It's nothing to do with lack of air suspension. It's just a fault.

Can't say I know what, but other cars don't do it and never have...

 

No S Type ever had air suspension. That was reserved for the top model XJ's.
Thankfully so as it was very failure prone and expensive to fix.

Any chance you can drive another S Type? So you can compare them?

My 2005 "R" has 126K miles and all the original suspension parts and still rides very well with no noises. I have the large 18" tires/wheels too.

Now if you get under the car you will see a number of split rubber boots that should be replaced. But all S Types have that by now so don't get to alarmed.
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No suspension probs as it's 10y.o. but still only 16k. I'm thinking it's the wobbly Michelins, thigh that's an unusual feature of Mich as they tend to have a soft ride. And this is FL with generally smooth roads though nothing like they were in 20-30 years ago. I'll have to meet up with another S owner and see if we can swap rides.

Love the handling though, so flat for a cruiser through turns.

 

And what is the sport suspension? Just an adjustable shock?