The V8 Owners Forum -

i have a jag irs fitted to my kit car weighing around 800kgs what dampers would you suggest and what poundage should i have for the 4 coil springs

Hi
Now you are asking!
working on the basis that a jag is about a ton and a half I would go for a first aproximation of about half the spring rate of what you already have, as for damping rate, I would think to match it about 2/3 the rate for the jag, that is based in the wheel/ tyre combination having about 20% less mass than the jag wheel/tyre. That is jast guess work, you will have to use trial and error (and asking anyone with a similar car) to get it sorted.
I would go for a set of good quality adjustable dampers with removable springs and you will just have to try it.
As a first aproximation you could just remove one shock off each side and see how it sits to and try the simple push down on the wing and watch it return to static height (should do it in with a single overshoot of static height of about 15% deflection) then settle straight to ride height. this will only tell you if you are in the ball park on spring rate but it is a start.
Best of luck
Mike

If you want a comfy ride around 100lb on the rear going up to 140lb for a much firmer ride and about 160lb on the front going upto 220lb for a firm ride. I'm using 100lb on the rear and 160lb on the front of my Melos with a RV8 and a car weight of around 870kgs. My front shocks are fully adjustable so I do have the potential to firm them up a bit if I want. If the rear is too soft I may just get some spring assisters from Halfords.

Dosent quite work out as a simple equation with the Jag Irs as the springs are slightly inboard, and have leverage issues built into the equations,then the spring rate is halved because you run 2 on each side.
The person to ask is Devon Man, Denis has been running Jag IRSs for years.

Minefield ! at a guess try about 400lb single shocks, and a lot will depend on how narrow it is, have a look at mine on a pop, about 650lb, no idea wot the original jag ones are and about 1300kgs !
http://community.webshots.com/album/555984531OGWDyt