Lifting wheels off ground with Air Suspension ok or not?

[Sonic]

Originally Posted by Dav L

The seals have nothing whatsoever to do with any damage from hanging from the shocks. As a matter of fact, since the shock is extended, the pressure (gas pressure) is less than when it's on the ground, so there is less issue with a seal failure when the shock is extended. Not that there is any issue of seal failure when down on the road either when the rig is static.

There is no stress on the seals when the shock isn't moving. So I discount that mechanic's understanding of the things he replaces....

Again, the potential airbag and shock damage is Freightliner’s position as relayed by their training department, not the opinion of a mechanic.
The airbag unseating is by far the bigger concern.
I’ve come to the conclusion that it’s cya on Freightliner’s part, but they’re really adamant about this potential damage.
I’m done with this thread

[Dav L]

Originally Posted by Sonic

Again, the potential airbag and shock damage is Freightliner’s position as relayed by their training department, not the opinion of a mechanic.
The airbag unseating is by far the bigger concern.
I’ve come to the conclusion that it’s cya on Freightliner’s part, but they’re really adamant about this potential damage.
I’m done with this thread

Y, passing on the info is fine...but when I hear uninformed stuff like "shock seal damage" or "it's ok for a little while but not for a long time", then the rest of the source is questioned.

I agree with their conclusion that you should not lift the wheels off the ground if you don't need to. But not for the reasons cited. The real reasons are:
1) Additional sidewards leverage on the leveler cylinders. If the cylinders are wimpy, then that can be a problem if something slips due to not being level.

2) Possibility of a hydraulic hose failure. One leg drops and twists the chassis. I just yesterday replaced 4) 45' hoses on my Man Lift...they do fail.

3) The temptation for storing stuff under the RV or kids hiding underneath.

4) That if one end of the rig is up in the air, and the other is down, then that implies you are on a steep slope. Not good for slippage.

Yup, thread is beaten into the ground.

[VanDiemen23]

I'll add one thing I didn't see in here:

before you take them all the way up, do a good visual inspection. My front axle has limit straps, so good to go there.

The rear, well yeah, there's the limits imposed by the shocks. You hope that occurs before you use the U-joints and driveshaft yoke as a limiter - probably OK, but if you can avoid it, why not avoid it.

But I found that the actual limiter on my rears was the left side brake line. There have been plenty of times where I'm doing some work and need a couple of inches more, but without limit straps, I don't want to stress something else. If I need to really get it up there, then I suppose a couple of 3 inch ratchet straps between the drive axle and the crossmember would be the way to go.

[Domo]

Originally Posted by twinboat

How is that ? Do the jacks being driven into the ground by the weight of the chassis slide ?

Does your table, grill, chairs, slide down the site ? Do you have brakes in them ?

Gravity pushes straight down, not down hill. You need wheels for that.

I did rear brake jobs on large trucks, when I jacked them up, they stayed right where I parked them.

Bow to stern movement was cited as the issue. The reader is allowed to use their imagination of how much and what caused the bow to stern movement.

To me - anything raised on a pillar can be pushed over. Granted, the amount of force may be enormous - but still... I'd hate to have both axles off the ground while on a hill and get bumped by my neighbor's RV as he leaves his site.

But, thanks anyway - and yes, I do trust gravity. Sorry you didn't have the same image come to mind.

[hewebb]

My driveway requires that the rear wheels are off the ground to get the coach close to level. I use wheel stops on the front wheels to keep the coach from rolling down the driveway. I sits like that for several days when either working on it or preparing for travel. I cannot believe that is bad for the coach.

[Jzack]

All suspensions should be designed to be topped out safely. It would be an engineering failure if this were not true. I've hauled 45,000# steel coils on an air ride truck and trailer. When the crane lifts the coil off the truck the suspension tops out HARD on the shocks. Never an issue after many years of this abuse. Also, as was mentioned, how else would shops with frame lifts work on them? IMO, Freightliners position is probably to prevent culpability on their part if something DOES happen.

We just came back from a trip where our front axle hung in the air all weekend. My main concern was when lowering the jacks and having the deflated air bag bellows (the rubber part) get pinched between their mounting plates. I tried to inflate the bags a little before lowering but realized the leveler valve prevents inflation until the axle is lowered of course. Ended up not being an issue but I could see this happening eventually and possibly damaging the air bag. I think it's telling though that after 61 posts not a single person has chimed in reporting damage to their air ride coach from hanging an axle.

[Domo]

Originally Posted by Jzack

All suspensions should be designed to be topped out safely. It would be an engineering failure if this were not true. ......

I think it's telling though that after 61 posts not a single person has chimed in reporting damage to their air ride coach from hanging an axle.

^^^ Yes - this! ^^^^

[Dav L]

Originally Posted by Jzack

All suspensions should be designed to be topped out safely. It would be an engineering failure if this were not true.

I think it's telling though that after 61 posts not a single person has chimed in reporting damage to their air ride coach from hanging an axle.

Yup. All vehicles are designed to top out. Hanging an axle does nothing. Just looks funny. So people think "that just isn't right".

Same as lifting the wheels off that then looses the parking brake...well if it's on level ground - who cares?

The only thing that comes to mind is pulling a bit on old stiff air bags. But they are designed to go full suspension travel.

[Kelpro]

Airbag pedestal separation does occur when the chassis is lifted to the point of the wheels near or leaving the ground. Not always but it does happen. The airbag upper plate is roll formed clenching the rubber and will not separate from the bag. However, The lower pedestal is attached to the bag like a tire to a rim with a bead and this bead is very small and will separate when stretched. It’s unfortunate FCCC use this type of air spring.

[ArtJoyce]

As long as you bleed the air out of the air bags. I'm with the others, you are fine having the front axle off the ground. Rear axle the tires should always be touching the ground. You can lift the rear some, but keep the tires touching the ground.

[shootist]

You want to hang all that weight off your shocks and stretch the airbags way beyond their normal travel? I just liked keeping my coach up high when parked with the full air suspension and leveling. My bags cracked around the top where they made the 90 down. I don't think it was coincidence. I don't do it to the new bags.

[Cloud Dancer]

Yep. the force of gravity is vertical, plumb vertical. And, it works through the center of mass of the vehicle. If it's on jacks, on a hillside, there will be bending moments there somewhere.

[Props2]

Originally Posted by Kelpro

Airbag pedestal separation does occur when the chassis is lifted to the point of the wheels near or leaving the ground. Not always but it does happen. The airbag upper plate is roll formed clenching the rubber and will not separate from the bag. However, The lower pedestal is attached to the bag like a tire to a rim with a bead and this bead is very small and will separate when stretched. It’s unfortunate FCCC use this type of air spring.

You are absolutely correct. My driver side rear air spring has done just that. I was lucky enough to find a replacement bag with in 60 miles of our home.They are in extremely short supply for my rig. Mobile tech will be out next week to change it.

This airbag gave me fits in the winter of 2018 in Arizona when it separated. I am not really sure why this happened but long story short, a mobile mechanic was able to reset it. I had it inspected in Gaffney and they said it was fine. Three years of no issues. Fast forward and just completed yearly chassis maintenance and what do you know. It has separated again. My suspicion is the facility used a jack to do the air dryer service which is between the frame rails. The bag probably partially resealed to get home. As the coach air'd down the bag just folded into itself. I tried re-sealing it to no success. The separation is off the lower perch. I can see a smaller diameter bead inside the bag which appears to snap over an inner bumper, for lack of a better word, on the lower perch The outer bead just rest on the lower perch. The rest of the bag looks fine. Gaffney said this was a very rare occurrence, but it happened to me. I will post pictures of the failed bag after it is removed later this week. This is just another learning experience for me and perhaps the caution that needs to take place for future chassis service.

[RV Driver]

I have never understood the fear of lifting wheels off the ground with the jacks. That’s what they are there for!

My coach sat like this for two weeks with no problems whatsoever.