Dr-z400sm suspension mod
 

I want 2 get a stiffer spring in the rear of my bike. but i have a few questions first. I have found a good deal on a race tech spring, what do you know about the quality of racetech? what other brands do you recommend? How do i know what weight in KG do i need when i order the spring? do I need to do the front springs if i do the rear?

thanks for the help