View Full Version : Air Pressure Adjustment

dale farley
06-23-2014, 07:01 PM
How do I adjust the air pressure for my main systems? My pressure normally stays close to 130, and I would like to adjust it to about 125.

06-23-2014, 08:28 PM
Adjust the governor on the compressor. It faces downward on the rear of the compressor with a plastic cover over it. Under the cover is an adjuster with locking nut. It doesn't take much movement to make an adjustment. I forget which way you have to turn it.

Joe Camper
06-24-2014, 07:43 AM
Wow imagine that a bus with air pressure at 130 PSI and it was not me that put it there but id be more than happy to be blamed for it.

Id leave it alone Dale it isint hurting anything probably helps to some degree.

06-24-2014, 08:35 AM
Wait Joe.....I think maybe some finger printing needs to happen...you are the only one who has ever adjusted air pressure!

dale farley
06-24-2014, 09:12 AM
Won't the higher pressure give me a little stiffer ride? I don't know how much difference 5 pounds will make, but it seems to me it is just unnecessary pressure on all the lines and components unless I really need that added pressure for some reason. I know Joe has raised the pressure because of the weight on some of the buses (and that makes sense), but I don't think that should be an issue on mine.

06-24-2014, 12:17 PM
The pressure shouldn't affect ride, within reason. The bags are regulated by the ride height valves and the ride is determined by the actual bag used. I do agree that higher pressure may may the suspension more reactive. The biggest change air pressure will likely be seen is in leveling the coach when parked and how fast the tag axle lifts or should I say how fast the drive bags recover from raising the tag.

FWIW, based on the research I've done, 130psi is acceptable, but is the upper limit. It's important to have a trusted gauge, especially when setting the pressure at the upper limits.

If your actual pressure is 130, you are okay. Here's what is commonly stated:

To INCREASE pressure, remove the black cover from the end of the governor, loosen the 7/16" jam-nut, and turn the adjusting screw OUT 1/4 turn at a time (about 4 psi) until the desired pressure cut-out is reached. Then, holding the adjusting screw in place, tighten the jam-nut and replace the cover.

Lowering the pressure is exactly the same except you turn the adjusting screw IN, then lock it with the jam-nut and replace the cover.

It is often necessary to "pump down" the system to 90 PSI of less to force the govornor to cycle the compressor on so you can know what the new cut-out pressure will be.

Anything between 120 PSI and 130 PSI is acceptable, I prefer to be on the high side.

dale farley
06-24-2014, 01:59 PM
It seems to me that I have a stiffer ride than I did in the CC. It may be because I have more air in all my tires than I did in the CC. I need to get my bus weighed and set my air accordingly. At this time, every tire has between 115 to 125 lbs. Significantly more than what I ran in the previous bus. I think I previously ran about 115 in my steers and 90 in the drives. I have left the higher pressures in this one since replacing the tires because I don't know the weight and had rather be high than low.

Joe Camper
06-25-2014, 07:59 AM
U have a slide coach and u need more pressure in the steer axle bags than u had in the steer axle bags on the non slide coach to get to the same ride height.

One of these days im going to put an air gauge on the steer bags on a slide bus just to see what it is.

Anybody want to venture a guess. I usually enjoy going out on a limb. Bet its up around 100.

A loaded semi is about 60 or 70 PSI in the bags when loaded (20psi empty) but is not a good reference they do not have air steer axles.

Making an air pressure adjustment either way has absolutely no effect on the feel of the ride. Not 1 bit.

06-25-2014, 09:14 AM
Joe, you hit on something I've wondered about. My assumption has always been that Prevost sized the bags for the rated wheel position weights, not their actual capacity but Prevost's rating. I say wheel position rather than axle rating because the coach's leveling system levels both left and right and fore and aft. If a converter exceeds that weight then the bags may be subjected to excessive pressure and hence stiffer ride.

As good as the converters are, those that installed their own slides may have a wheel position weight that exceeds Prevost's engineering. Let's not overlook our own loads. If you carry a lot of heavy stuff you need to plan for its placement.

Dale, what shocks do you have up front? Koni's set to anything but the softest setting can contribute to a stiff ride.

06-25-2014, 11:13 AM
Joe,I would agree that the pressure in the bags on a slide coach would be at least 100 PSI,when I raise the front of my coach it takes at least 100 to get started.

TG Transport
07-15-2018, 08:12 AM
I found this old thread yesterday and used it to adjust my pressure limit. My regulator faces the engine block so I had to do this blindly. Gil's answer is dead on. It took a 7/16" socket to loosen the jamb nut and three quarter turns raised my pressure about 12 psi.