Originally Posted by 30Tooth

Going by the chart I found they are 17lbs/in which is around 300gr/cm, if the rating is true then you've the same spring rate as I run on my TC6 with hpi silvers which are also 17lbs/in.

According to this site, 310gr/cm is Xrays 3.0 spring rate so you have to chose if you want 3.0(310gr) or 2.8(290gr) xray spring. That's tire dependent as I've said before, soft tire soft suspension and vice versa.