I am in the same boat as I have changed the weight of my 818S project. Added weight with structural components in the front, middle and rear. Now to get the rear to 5 inches the rear adjuster is near the limit.
After spending two nights looking at all the posts about spring rates I am more confused. Street driven only, No Aero, I am focusing on 400 rear springs and 500 fronts to eliminate burning the fenders with the front tires and bottoming out on speed bumps. When I carted 165 miles all was good but then added the body and extras now the adjusters are maxxed in the rear.
Are these spring rates consistent with the new normal??
I read Jim Shenck mentioned putting the 500 in front and the 350 in the rear on a non raced street version of the R.
Here's a quote from the R supplemental instructions.
" The front shocks are pre-valved at the factory in compression and rebound for good street use. The
shocks can be adjusted in rebound as per Koni’s instructions if so desired. The front springs are
500lb. Other springs are available for different ride characteristics."
Thanks Guys for your hard work and dedication to theses projects!! Don