Let's talk air bags...
My 1999 7.3 dually has airbags installed by the previous owner. I've generally not bothered to inflate them unless towing a trailer with my Bigfoot camper (4000lbs loaded). Today while driving on Cali...
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If they are Firestone then do not run below 5psi ever. When the truck suspension tops out it will pull a vacuum on the bags and could damage them or rip them. You need enough air in them to prevent this vacuum. It will be the same with any brand.
Guys that say bag can only stiffen the ride are dead wrong. There is much more to suspension dynamics than just a knee-jerk reaction can offer.
Your truck springs will have a neutral point, the point which the springs are neither supporting weight nor pulling in the opposite direction. This would be where the leaf springs are curved to the same shape as if they were off the truck and sitting on the ground. I do not include coil springs here as they are not necessarily attached such that they can pull.
I only have data for two-wheeled vehicles from here, but on those you can soften the suspension with a strong spring that has an opposing spring pulling/pushing the opposite direction. This set-up tends to overcome the friction in the suspension linkage that would otherwise cause you to lose some of the small bump compliance.
ON a truck there is probably a small window where you can lift the truck just past the neutral spring height where the air bag is lifting the truck and the leaf spring is trying to pull the truck back down. Opposing spring forces. Go too far and you will just get a harsher ride.
Both trucks I put bags on would ride much smoother with some air in the bags. 10-15psi on mine.
On your 1999 you will for sure have spring sag from age, so using the bag to correct the sag will both improve your ride height and maybe even handling when unloaded.
I do not make any scientific claims on truck suspension but am only comparing two-wheeled set-ups to the truck and also my personal experience that supports the fact that my trucks were smoother with air in the bags.
Guys that say bag can only stiffen the ride are dead wrong. There is much more to suspension dynamics than just a knee-jerk reaction can offer.
Your truck springs will have a neutral point, the point which the springs are neither supporting weight nor pulling in the opposite direction. This would be where the leaf springs are curved to the same shape as if they were off the truck and sitting on the ground. I do not include coil springs here as they are not necessarily attached such that they can pull.
I only have data for two-wheeled vehicles from here, but on those you can soften the suspension with a strong spring that has an opposing spring pulling/pushing the opposite direction. This set-up tends to overcome the friction in the suspension linkage that would otherwise cause you to lose some of the small bump compliance.
ON a truck there is probably a small window where you can lift the truck just past the neutral spring height where the air bag is lifting the truck and the leaf spring is trying to pull the truck back down. Opposing spring forces. Go too far and you will just get a harsher ride.
Both trucks I put bags on would ride much smoother with some air in the bags. 10-15psi on mine.
On your 1999 you will for sure have spring sag from age, so using the bag to correct the sag will both improve your ride height and maybe even handling when unloaded.
I do not make any scientific claims on truck suspension but am only comparing two-wheeled set-ups to the truck and also my personal experience that supports the fact that my trucks were smoother with air in the bags.
