[SCOTI]

Originally Posted by fleetman

thanks for the reply -
so if i have a load - is determining max bag pressure as simple as the psi read at the valve to the bag ?
forgive a simple question .. but say a 2500 bag replaces the stock spring.... what is new unweighted bed height ? or am i missing something here ?
thanks
paul

Double convoluted bags @ normal/average pressures typically yield 5.5" heights minimum. Typical factory coil springs in a 6x-72 1/2 ton truck arm app range from 8.5-9.5" tall so figure about 3" drop. Manufacturer suggested/recommended pressures typically are up to 100psi but it depends on the exact mfr & type of bag.

For example.... My 68 had bags swapped in place for coils (I used Firestones). I originally used the larger 2600#/7"/RE-7 size bags (which are slightly taller) & the recommended installation brackets. This combo of parts ultimately only required about 25psi to achieve the ride height I was targeting & rode like crap (very bouncy). To 'correct' this, I 1st removed the 'installation' bracket which removed about 1.5" from the installed height. This combo required about 30psi to achieve my targeted height. The ride was better, but still soft. The best ride required dropping to the smaller 2500#/6"/RE-6 size bag which required about 35psi minimum & provided a very nice ride quality.

With a loaded bed (or when I hooked-up my 18ft car trailer to pull another truck), bag psi typically was about 65psi.