The XK is relatively new to me, about a year and done very few miles while I've worked through the essential repairs/maintenance. What I had last year though was very twitchy steering, like massive oversteer, at speed and also a vibration through the steering wheel that came in waves. Over the winter I've completely overhauled the front suspension, new joints, bushes, vee mounts, shock bushes, roll bar bushes and track-rod ends. The shocks themselves appeared ok as did the upper mounts and roll bar links which were all left alone.
I had the wheel alignment checked/adjusted last weekend, the cambers were all out of spec (high) which can be put down to settling of the springs I guess although the ride height is within spec. The castors were both out even though the spacer packs were installed to original specs. Figures are 5:26 and 5:40. So firstly two questions arise, is it worth getting eccentric wishbone bolts to adjust the camber and is it worth re-setting the castor (that's assuming the adjustment range is sufficient)?
However, I can't understand why the steering is still to twitchy, as I said in the title the x-type is actually better and feels a lot safer and controllable at speed that the XK. My tyres are practically new Avon ZZ3 rear and half worn Dunlop sport on the front. The Dunlops are slightly concave when looked edge on so I guess have been overinflated at some point. The vibration is still present but only just detectable and only when instigated by some roughness in the road surface.
Where should I be looking next?

the x type is a 4 wheel drive if ime not mistaken as i also use to have the 3.0s xtype and i would consider my xk8 to be just as good if not better,hope you get it sorted

Thanks Graham, actually my X is a FWD diesel estate which makes this situation even more worrying!

dont give up mark it will be werth it in the end

Just a thought...What's the rear suspension looking like . Any play there ?

TBH I haven't looked at the rear, there isn't any bangs or rattles but then there weren't from the front either. What should I be looking at?

Longer wheelbase cars handle better "at speed". It is why racers prefer 2+2 chassis for race cars over 2 seaters.

You absolutely need both rear & front suspension in good shape - all parts - and proper alignment afterwards if you change anything. The car is driven forwards by the rear so of course it must be right.

Indeed, couldn't agree more. Front is all new and aligned except as mentioned which appears to be par for the course, what are the replacables on the rear?

That and an estate body is going to have far less flex in it than a convertible if we think about it. It's quite possible to make even a Volvo wagon out handle an Aston convertible in chicaney conditions.

This is one of the things I'm trying to mitigate on my XKR (started a thread last week on this). How do I strengthen the rear up? Well, I could just weld in a giant roll cage toward the back, cut off the boot lid and add a hatch!

Bringing out the popcorn as we speak!..