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It really depends how aggressive your shock absorbers are.

For street driven cars most of my customers run between 5 and 7kg in the front and between 4 and 7kg in the rear.

Spring rates should be selected based on corner weights, nothing to do with engine power the car could have 100hp or 1000hp, what matters is the weight over the individual corner and how much load is transfered to it during cornering (this is worked out using a combination of data ride height/suspension travel/motion ratio etc)

You should be able to find a formulas to work it out on the net but you will have to do some research its not really something which can be explained in a short post

8/4 is wrong wrong wrong. GTR is an inherently understeery platform (throttle oversteer notithstanding). As such, you don't want to be running double the spring rate at the front that you have at the rear. If you want to run 4 at the rear, no more than 6 at the front. If you want to run 8 at the front, then no less than 5 at the rear. Then you have to valve or adjust the dampers to suit and then you have to select anti-roll bar rates to tune the over/understeer balance.

and the more power you have, the more traction you need, so the softer the spring should be. But I can't see why you would expect much traction with 500+kw on street tyres on typically variable street surfaces. I'd always assumed that if you want that much power you *don't* want traction....so put some stiff springs in :)

Are you only interested in straight line?

8Fr 4Rr will be horrible for going around corners (missmatched), like 12Fr 12Rr is horrible (too hard, mismatched). If you're running the Super Streets use the Super Street springs - they are correctly matched front to rear and they'll match the valving - 6Fr 4Rr IIRC.

A mate of mine has a 600kw at all 4s with 6kg all round. Hooks up ok.

What tyre is under it has more to do with how much traction you have rather than spring rate. GTRs at this level squat hard under WOT so you still need a bit of stiffness.

I have 6s all around too.

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