Replacement Air Bags

[Jon Wehrenberg]

Tom,

Will the front of your bus raise from the full down position to the full up position without lifting the tag?

Can you speculate and let us know what aux air pressure it takes to raise the front to ride height?

It sounds like you have the correct fronts. The number for the rears corresponds with the one on my drive axle only. The tag has 630126.

For those whose front air bags are part number 630260 it is possible that air bag is for a seated bus, and that is why you cannot get full up travel. Apparently that is the air bag number that will be supplied and it is not suitable for a motorhome which relies upon the level low system for leveling.

[Joe Cannarozzi]

Well if Brian was given the 0259's then SOMEONE at prevo parts got it right.

Who was it?

I got a notion to put the 0260's on the front on ours we have a 11800 front end and I would like to know if they would lift a lighter load or if the travel is just not enough.

[truk4u]

Jon,

It takes full shop air at 120 psi to move it very slowly with the tag down. I just took it off the stands/blocks and had to cycle the shop compressor to keep the pressure high or it wouldn't come off the stands.

If the bus is running, it takes high idle and all the air it can make to move it. The front end is at gross weight, 14,000 lbs. At Mobile, I had to dump the tag to get the front up.

100 lbs of air will not lift the front

[BrianE]

Tom, yer a crybaby on this one. I doubt if 100 psi will lift the front of anyone's bus. It sure won't lift the Royale. In my short experience with the Prevost level lo system, the Liberty leveling system is far superior IMHO. Have you sorted out the Aux air problem you were having? With a leaking check valve you might not be getting enough volume to the airbags. Just a thought.

[Jon Wehrenberg]

Hate to disagree with you guys, but 100 PSI will bring my front up to almost road height. I am carrying a little over 14,000 on the front. I know this for sure because those that have seen my driveway will understand I have to drop my front to get throught the overhead door, and raise the front once outside so the baffle under the generator doesn't get crushed on the crown of the driveway. So every time the bus goes into or out of the garage I have to run the front up and down throught its maximum range of travel.

My rears come to ride height with less than 100 PSI.

My old bus with about 13,200 on the front required full pressure and a lot of time to come up to the max height and 100 PSI (aux compressor cut out) would only bring it up if the tag was lifted.

I have 630126 (1R11 296) bags in the front. Now I am really curious about exactly what bags our coaches need to have. Since Tom's coach and mine are raising almost the same weight then it follows that our air bags are different because of the different pressures required. That leads me to conclude the 630259 is NOT a direct replacement for 630126.

The plot thickens. When Dr. Joe C. changes a set of fronts this coming weekend I hope he can get some measurements. Diameter when installed deflated (at full height), maximum extended height (mounting plate on bottom to mounting plate on top), pressure at ride height, pressure to fully extend.

[truk4u]

Mole Man - The suspected check valve (if there is one) has nothing to do with this pressure issue. I would suspect the bus will go to road height at 100lbs given enough time, but beyond that, forget it. However, the rear bags seem to have no problem raising even at less than max air pressure.

The 40' Marathon I had experienced the same. It would not lift the front without dropping the tag. The CC on the other hand would come right up. The Marathon was also at max gross on the front end, same as the Liberty. The CC was about 2000 lbs under gross on the front.

Jon - Keep digging, with Joe's help, we may find there is a better alternative to the front bag issue. It appears to me the 259 bags just can't lift 14,000 lbs without help. Maybe that's just the way it is! Mine is still hooked to a 100 gallon shop compressor, so I can do a little experimenting if needed.

[Jamie Bradford]

How often do air bags need to be replaced?? Is it ok for the bus to sit for a week or more with all of the air dumped? Or should some be left in the bags?


Jamie

[BrianE]

Jamie,

That's always a good question to ask. It's probably fair to say that when not in use, the typical bus suspension will leak down in as little as 2 days and as long as a week. Consequently, many coaches sit for long periods of time with flat airbags and it doesn't seem to effect them much. However, if you look at them when flat they look pretty bad so a number of us have been using Jon's custom built stands (blocks will work) to support them when in storage. Over time the stands probably make the airbags last longer.

As to how long they last, it varies depending on a number of factors but atmospheric conditions and time in storage are probably the main considerations. Like all rubber components they deteriorate with time. I personally start looking at them and at rubber brake lines with suspicion after 5 years.

[Jon Wehrenberg]

Jamie,

The Prevost position expressed in Branson was that they are OK as long as they are holding air.

I disagree and here is why. Several of us have had problems with air bags as they reached 10 years of age. I have gone through this twice now with two different coaches and when my bags were 10 years old I had one leak due to corrosion on the metal base, and all air bags showed signs of serious dry rot. If I am not mistaken there have been at least 4 other POG members that had issues with 10 year old bags.

The problem with waiting for an air bag problem before reacting is the serious nature of a leak, or worse a blowout of an air bag. You cannot drive a bus that has a failed airbag. It is literally sitting on the ground in the front or left or right rear. When one does fail such that your bus cannot produce enough air to overcome the leak you can get off the road, but you cannot travel. These are not something you can buy at the local truck parts house. In fact I cannot find anyone listing the trade numbers we use on the internet as stock items. So a leak or failure shuts you down until it is replaced.

There are guys here with 15 year old coaches that still have the original air bags. I think the condition of the air bags should be the deciding factor. For me, based on anecdotal evidence only I am going to replace mine every ten years. I don't think you are in need of replacements yet, but every time you are beneath the coach you should look closely at them. Look for cracking or dry rot around the bottom where they roll. That is where it shows up first.

[Joe Cannarozzi]

Jamie there is a large rubber bumper attached the the inside of the top plate on the air bags. When you go all the way down it settles on that rubber block and absolutely no harm will come to doing that.

I have pulled 2 sets of bags off 91's and they were so cracked and dry it is amazing they even held air.

I have also pulled ones that were already replaced once so not too old, 7 & 8 yr and cracking was not bad but already beginning. Jons suggestion of 10 yr lifespan is a good call.

If the 0259 does not do any better that the 0260 I am going to be very upset.

I sent Orren a PM with the industry #s for the 630126 that original may wast bag and if he can cross it to another manufacture I will buy them and will put all 3 set of bags one at a time on our bus and note the results. Just maybe we can solve a large shortcoming that Prevo is aware of probably has been for some time and is unwilling to correct.