Chassis Trivia Question

[Hoffman]

I have an 01 and it has 365's. They fit. Mostly. Almost always...
My issue is that I have to wait a long time for the air to come up to proper ride height. Any early departure results in scraping noises, mostly from the mud flaps dragging. But once fully inflated I don't have issues with the 365's.
I don't know if they were original or an upgrade. From this thread it sounds like my 365's were an upgrade.

[Joe Camper]

Maybe i can help u with that. Where does the brake tank pressures build to, exactly, do u know? Do they top out at 120 exactly or do they go higher?

I'm not sure if there was any clearance issues on the upgrade on the Hs they maybe had a bigger wheelwell as was. It was the xls that get changed to 365 those chassis, those front wheel wells r tight tight tight with 365s.

Back to front suspension and air pressures. The 07 XLII DS chassis I'm currently rubbing on, it's set at 135psi and I didn't put it there someone else did imagine that. It Needs it every bit of it.

Consider this.

On this DS 07 but really any DS with a heavier front axle If I get the air pressure down by pumping the brakes to get the compressor pumping on this chassis and at low idle I stay on the up button in the front position in level low and hold it till the aux air pressure gauge hits 120 exactly then stop the front of the bus is barley at ride height. If i repeat the process but stay on the up button till the air dryer sneezes at 135 the front end is 3 or 4 in up above ride height.

There also is the possibility the ride height is misadjusted . Could also be if u have blown front swey bar bushings the ride height valve linkage is mounted to the swey bar on the steer axle and if the bushings r completely blown out, and I've seen that plenty, then the ride height will drop and a lot.

Also try this, do not use high idle when airing up. Then after it has achieved max pressure and the dryer sneezes go take a measurement somewhere on the front end to the ground . Then pump the brakes down to below 90 to get the compressor pumping again and in low idle again let the pressure build to max till the air dryer discharges again. Maybe just for testing do this a third time then go back and measure again. Not in level low, in driving mode u r doing this test. If the problem is a marginal pressure cut off setting the height in front could over time creep up over time. Others have had similar complaints and performance. Initally first light fronts low few hrs down the road everything's higher. Marginal max setting. If this proves true and it's not the height adjustment or the swey bar bushings, until u get it corrected just cycle the air compressor like this first thing few times before u roll and yer golden.

135 is as high as I'd ever set one but even going up 5 psi to 125 or 130 often generates great results when u r experiencing this situation.

[Hoffman]

Brake tank pressure builds to 120+. Sometimes when driving i notice it more around 125+, then it settles down.
But I may be able to answer my own mystery. 2 weeks ago I learned that I had a bad leak in the braided air supply line coming out of the compressor on the engine. I'm working to get that replaced, not as easy as I would think. But given the loss rate when the compressor is running, i'm excited to see how much faster it comes up to pressure when I get that leak fixed. I'm not scheduled to go anywhere until December, so I have some time to deal with it. I'm currently in Indio, CA. for the winter. I had a guy in Beumont, CA who was going to fix it, but I've not heard back from him in a week. He was going to have a shop build a custom air line as Prevost seemed reluctant to send him the "only one in the US", located in Tennessee. This is a braided line running from the compressor to an air dryer (?) just above the drive axle. About 15' (?) in length.
Once I get this leak fixed, i definitely want to explore your theories and revisit this.

[Joe Camper]

Good luck and keep us posted.

I'd have the mechanic who installs the line turn the regulator up to get the cut out at 130. Even if the condition is being caused by misadjusted ride height or blown swey bar bushings turn the air regulators up to 130 on the slide chassis. That's where they need to be.

[Joe Camper]

Another trivia. When did Alcoa enlarge the holes on the 9 in rims to match the size of the holes on the 8 1/4 in rims??

The old smaller holes make it unbelievably difficult to air up with conventional stems. These newer larger holes u dont need any of the additional crap attached to stems to get er done. They look pretty good too. U can check pressures again, normally, the old fashion way in about 2 min with a gauge in yer hand. Imagine that.

When did this change occur? I dont have the answer.

Wonder what alcoa would say about enlarging the holes on the old style. It's a safety issue if it's difficult to check yer tires generally speaking u will do it less often. Hmmm