I've never seen any published spring rates, but the major difference on the 'R' is that the rear springs are 1 1/2 coils shorter, which results in the car setting level instead of the usual rake. R's all have bilstein shocks. You can buy the idler pulley and bracket from Mazda, but I might have them on my Spec Miata-to-be. Will let you know.....Originally Posted by homerneedspeed