Air Bag Ride Height Dimension - 259 Bag

Anyone have the measurement for the bags on an XL, I can't find it? The measurement is from the top plate to the bottom plate I think.

Tom, I think if you call Prevo parts the salesman can tell you that dim.

JIM;):D

Tom,

On page 16-29 of my maintenance manual, it says the measurement for the front air bag is 11.7 inches at normal operating air pressure of 95-125 psI. The measurement is from the top to the bottom of the plates.

The rear bag measurement should be 11.5 +- .25". Hope this helps.

Dale,

Don't confuse air bag measurments with the Prevost recommended ride height measurements.

The dimensions you cite I think are the dimensions you wish to obtain when adjusting the ride height valve arms. That dimension can be adjusted up or down, but what Prevost specifies is what they want the ride height to be.

The air bags will actually extend to a greater height, limited only by the shock absorber travel and dependent upon aux system pressure.

What I'm trying to do is make sure my ride height is within spec. After replacing my travel coil/valve, the bus now seems to be setting too high and changing those components should have no effect on ride height (measured from the bottom of the bus just behind the front wheels and just in front of the rear wheels). The air bags are right at 12" when measured from top plate to bottom plate and the ride height is 11 1/2" measured from the bottom of the stainless to the floor as mentioned above.

So which measurement is the real ride height number Jon Boy?

Thanks Dale, I don't have the Prevost maintenance manual unless Brian hid it.

Tom,

My scanner is not working, so I made pictures from the maintenance manual.

Tom,

Dale has it nailed. You are 3/10 of an inch too high, but that is less than 5/16" and I seriously doubt if you should monkey with that. The reason I say that is that there is a range of repeatability in the ride height valves. If you cycle the bus up several times and then go to the drive position and take measurements, and then cycle the bus down several times and return to the drive position and take measurments it is probable you will find a variation in those dimensions. If they are consistently high or low you can probably make an adjustment to bring it closer on average, but you will never be able to eliminate variations due to how the ride height valve works and even a little slop in the arm will have an effect.

Jon,

I've moved it up and down full travel several times and it does get pretty close each time, but your correct, there is a little variation. I think I'm good and when I bounce it down the road to Florida in Nov, I suspect there will be slight changes.

I'm going to record the height on each side from the stainless to the pavement and that would be a an easy reference for checking the height in the future without dealing with air bag measurements. I did that on the previous buses, but now have CRS!:o

For anyone playing with this ride height stuff, you have to keep up a good supply of aux air if your not running the engine. I attach shop air to the aux tank, then I can just stand outside the steering bay with the drivers window open and play with the level low buttons. This is strictly for measuring the body ride height and no underneath work! Never get under one without full blocking and bracing that has been discussed a gazillion times.

Tom/Jon,

I was playing with mine last week, measuring from the stainless to the floor. I was running my engine and would let the bus auto level at various heights then return to ride height. I noticed slight variations in the measurements. I am glad to hear the variations are normal.

THIS IS IN CAPS BECAUSE OF THE IMPORTANCE. TOM IS ABSOLUTELY CORRECT ABOUT NEVER GETTING UNDER THE BUS UNLESS IT IS SUPPORTED

ESPECIALLY IF YOU ARE MESSING WITH THE SUSPENSION VALVING

There are two types of ride height valves now installed on our coaches. One is instant acting (newer chassis models or those that have been changed) and the time delay ride height valves typically installed on older chassis.

If the coach is not supported, you can get surprised when monkeying around with ride height valves. Ironically, when adjusting the valves you need to allow the bus to go up or down so you can see the impact of adjustments that you make to the valve arm. My advice is to either get the bus over a pit so it can freely move up or down without putting you in a compromising position, or put it up on ramps, or verify you are in the wheel wells and will be unaffected if the chassis goes up or down.