Prevost Question

[bigred]

I just had new Prevost air bags installed and I don't know if I need to bring this to my repairman's attention or not,I thought new airbags would fix the problem but it does just like it did before IE when I hit the valve to raise the bogey's ,They raise but in the mean time the bus squats on the drive wheels. Depending on the lay of the land the bogey's at times will barely clear the ground but most of the time they just slide across the pavement .Is this as I have been told,the norm or is something out of adjustment??This is a 93 model.As usual ,thanks for your comment's and advice.

[lostagain]

In my experience with MCIs, when you raise the tags, the bus squats down on the drives like you describe, but raises again within a couple of minutes, because the leveling valves tell it to. Maybe the pressure regulator for the drive axle air bags isn't set high enough? So the bags are not getting enough air to raise back to normal level with the extra weight?

JC

[bobofthenorth]

My experience with our Prevost  was that JC's advice is what you should expect.

FWIW when you raise the tags you will transfer weight OFF the steers as well. IOW past the weight from the tags you will take some significant weight off the steers and add it to the drives. Despite all that added weight your ride height should not change one iota.

[muldoonman]

Never noticed mine going down and coming back up when raising tags for tight turning or backing. Tags will also clear the ground on mine. Have had bags, shocks and several valves installed that leaked. Prevost done the job.

[robertglines1]

Did you just ask  on PC.  Early 90's prevost got a idea. discontinued it about 95 of auto tag lift. Easy to change to correct problem but also easy to screw up.  Look at peumatic for something like my 98 when they went back to manual lift of tags.   bob

[scanzel]

I have an 89 Prevost and when I lift the tag to back into my tight driveway the tag lifts and clears the ground and the back settles slightly because of the extra weight. When the tag goes back down I can feel the back rise up slightly.

[Jon]

Big Red...........

Since yours is a 93 model you don't have any automatic tag dumping on turns nor do you have hydraulic stabilizers that were an option on 45 foot coaches in the mid nineties. When you lift the tag you losing the support of those air bags and the weight they carried is transferred to the drive axle along with some of the weight from the steer axle. Your drive axle air bags are now carrying what the tag axle carried at the very least. The typical Prevost conversion of your year was a relatively light coach compared to the coaches built today so after the coach initially squats, the four drive axle air bags will eventually restore the rear to the normal driving height. How much time that takes depends on how much weight the drive axle and tag carries normally.

[sixtyseven]

I had the same problem on my Prevost before and after new air bags.   After investigating I discovered the air cans that lifted the tag were filled with road crap because of the mounting angle.  Once I took them apart and cleaned them it worked much better.   Even when working correctly the tires don't rise much off the ground but enough they don't touch.  And yes, it's normal for it to drop until the fill valves catch up. 

[sixtyseven]

Also you need to make sure your ride height is adjusted correctly.

[bigred]

I maybe expecting to much of mine.I have been doing some investigating and it seems that on Prevost ,the bogey's lift very little and I was thinking they would lift like the older MCI'S .Never measured but they looked like they would clear the ground by six inches where the Prevost clears by one inch or less.One site that I went to showed an H3-45 with the bogey in the raised position and you really couldn't tell it was off the ground.

[Jon]

Early Prevost tag axles would clear the ground by at least a couple of inches IF you waited long enough for the pressure to build in the lift chamber (which I think is a #36 brake chamber) and you allowed the drive axle air bags to get enough air in them to return to the driving height.

Later model coaches are unlikely to lift the tag tires off the ground.

All this presumes everything is working OK.

[MB LeMirage]

On my 1980 LeMirage, when I lift the tag it is about 3-4 inches off the ground. It starts at about 1-2 inches and within a few second (maybe 10-15 at the most) the drive axle re adjusts and I get an extra 2 inches of lift for a total of 3-4. This is the stock system unmodified.
Ryan.

[luvrbus]

I don't believe on any 45 ft Prevost the tag will clear I never saw one that would clear enough to remove the wheel

[MB LeMirage]

I cant speak about a 45 since mine is a 40.
Ryan.

[luvrbus]

Prevost redesigned the tag on the 40ft in 1994 for clearance when using the 60 series and B500 they don't raise like the older models best I can tell