N15 made a big list yesterday:
http://micra-forum.com/showthread.ph...-for-k13-micra
I've thrown Tein super-street coilovers on mine but had the same issue trying to find what exactly stock specs are, based on the nismo series I'd assume the fronts are 2.5K, rear ~3K. - I've tested weight distribution on the K13 and some 70% of weight added to the driver / passenger seats is transferred to the rear (so they need to be stiffer) - reasons I'm moving to 15K in the rear. Most After market springs run near 3K in the front and 4-4.5 in the rear, so ride angle doesn't change that much.
There are polyurethan shims you can get cheaply that are inserted between the coils of a spring -> can be used in the rear to add height once loaded / reduce rearward tilt depending on how many passengers you've got.