'What can you fill a barrel with to make it weigh less/'

ans 'holes'. Still goes.

Please explain to me just how having my my springs 're-arced' & adding another 'leaf' will add another #600-#700 load carrying capacity to my truck ~~~~ WHEN I an at MAX GVWR. I know the added 'iron' will weigh a bunch.

My mind just does not wrap around that 'logic'

THANKS