Jag rear: shock length question

[Tom Wells]

I have a 3.8S (same as 420G) Jag rear.

Should the XKE rear shocks work, or do I need longer ones?

My present shocks are 13-1/2" eye-to-eye fully extended. When the car is lifted by the frame, the rear wheels only drop 1/2" before the shocks are extended to their maximum length.

There is about 1-5/8" of thread showing below the coil spring adjusting collar - the vendor said anything over 1" means a stiffer spring is needed.
The present springs are marked as 350# springs.

There are four coil-over units.

I think I need a longer shock - say 15".

Any expertise out there?

Tom

PS: This probably explains the handling problems where the rear "skips" sideways under spirited cornering on the racetrack, and also the "bobbing" or "pitching" when the car goes over bumps at speed - sometimes it bounces me 2" clear of the seat!

[Bob Putnam]

Tom,

If you only have 1/2" of rebound travel from normal ride height, you definitely need longer dampers. 15" extended length sounds about right, and 350 lb/in rate springs should work well with them. It sounds like you've got stock length lower control arms which may be incompatible with the XKE dampers.

[Tom Wells]

Hello Bob,

Thanks for the response. The 3.8S/420G wishbones and axles are intermediate between the XKE and the XJS. I forgot the specs because it has been so long since I researched this point, but I have used them uncut because they are fine widthwise.

The shock mounts are further outboard on the E-M frame to match them, and of course the lower mounts are further out on the wishbones than the E-Type. This puts the rear hubs an inch or so further out toward the center of the rear wheels.

Since I don't have the exact measurements I can't do the simple geometry. Intuitively, since the shocks are mounted a little further outboard, the stroke probably needs to be a bit more. It would be closer to the wheel, and therefore closer to the wheel travel, if that isn't too opaque a way of putting it

I'm off to see if I can swap these in - they're too dang expensive to just pitch and replace!

Regards,

Tom


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