Can I run the bags empty?
It will not hurt the bags to run empty, but the ride will be very harsh. When the bags are empty, you probably will not be able to turn very sharp because the tires will rub on the lower rear part of the fenders.
How tall can I run the bags?
Running the bags completely topped out will not only yield a harsh ride, but typically put the pinion angles, driveline and alignment out of specs. It will ride harsh because there is no rebound if they are topped out. When the bags are all the way up, the front left tire will tend to be sticking out of the front fender well farther than the right front.
Should the bottom of the bag be straight?
Not being straight will not hurt the bags. Air bags are run in industrial applications up to 30 degrees. We try to keep the bags straight as possible, but the bottoms may be angled a little as the pinion angle of the axle is set. As far as up and down goes, the kits are designed for the bags to set pretty square. If your application has an adjustable panhard bar, use that to make sure the axle has the same amount sticking out from side to side. Once this is equal, the bags should be straight.
Do the bags wear out?
As long as the bags do not have anything rubbing on them, they should last for years. Periodically check your bags to make sure nothing is rubbing on them and no rocks or debris has lodged in between the air bags and steel framework. Be sure to thoroughly wash the bags after mudding. Blowing a bag should be no rarer than getting a flat tire.
What should my bag’s height be?
Use the following chart to monitor your bags heights.
| Application | Bag # | No Air | Ride Height |
|---|---|---|---|
| F-450 / 550 4-link Rear 2WD & 4WD | 5323 | 4″ | 7–8″ |
| F-450 / 550 2-Bag Rear 2WD & 4WD | 5770 | 4″ | 7–8″ |
| F-450 / 550 2-Bag Front 2WD & 4WD | 8979 | 6.5″ | 11–12″ |
| F-650 / 750 2-Bag Rear | 9039 | 4″ | 7–8″ |
| C-4500 / 5500 4-link Rear 2WD | 9039 | 4″ | 7–8″ |
| C-4500 / 5500 4-link Rear 4WD | 9626 | 5″ | 12–13″ |
| C-4500 / 5500 2-Bag Rear 2WD & 4WD | 5770 | 4″ | 7–8″ |
| C-4500 / 5500 2-Bag Front 2WD & 4WD | 6905 | 3.5″ | 6–7″ |
| International / Freightliner 2-Bag Rear | 9039 | 4″ | 7–8″ |
Can I blow up a bag?
The bags are designed by Firestone to be operated at a maximum continuous pressure of 100 psi. The bags are also pressure tested to operate at over 300 pound spikes. With the air compressors that we use, it would be very difficult to blow up a bag.
