Retracting Jacks with a Spartan Chassis - Confession Time

[Ray,IN]

Originally Posted by mhudson

On our 2005 MM chassis everything moves forward about 4 to 5 inches. The front and rear tires roll forward and the house moves forward the same amount when dumping air.

First time I experienced this I freaked-out, re-read my owners manual and found it, front wheels can roll, rears cannot due to air brakes being set.

[AFChap]

Originally Posted by Ray,IN

First time I experienced this I freaked-out, re-read my owners manual and found it, front wheels can roll, rears cannot due to air brakes being set.

Rear wheels may not "roll" relative to the locked brakes & axle, but mine definitely appear to move forward ...I presume due to a cantilever effect of the body moving forward of the brake locked rear axle as the suspension "hinges" on the axle connection points. The first few times it happened to me the tires ...BOTH front & rear ...ended up on top of the tire covers. Since then I put the tire covers on only AFTER dumping air & leveling.

[Ray,IN]

Originally Posted by AFChap

Rear wheels may not "roll" relative to the locked brakes & axle, but mine definitely appear to move forward ...I presume due to a cantilever effect of the body moving forward of the brake locked rear axle as the suspension "hinges" on the axle connection points. The first few times it happened to me the tires ...BOTH front & rear ...ended up on top of the tire covers. Since then I put the tire covers on only AFTER dumping air & leveling.

Ya, that's the part that had me scratching my head and wondering if the parking brake was holding. I think my thread about this was in 2013, and I think you helped me understand.

[CoachStreamr]

Originally Posted by USMCRET

Ha! It's okay Sky Boss. I'm a slow learner myself. BTW, I had a guy on another forum who is allegedly a service tech proclaim loudly that there was something wrong with my coach. "No coach should ever roll anywhere with the parking brake applied. GET THAT FIXED. You're going to kill yourself." Okey dokey then.

So before taking into Cummins for service, airing up/dumping air did move the chassis at least 2-3 inches (at least) if I remember correctly. I thought that was a lot at the time but read here on the forum this was normal(?)

We have a long driveway that slopes down to the road and we have a gate up top that opens to our property. Currently, there is only about 3" of clearance on either side with the Coach's mirrors folded in so I stop a few feet before the gate and set the parking brake, the Coach rolled more than I thought was proper. BTW - We are in the process of moving one of the gate's brick columns approx 2 feet to widen the opening. This will also help the firetrucks that have also complained - I just didn't know how big a deal this was until I drove through our gate a couple times.

I did report this to Cummins when we dropped off the Coach. They said they would look at it as part of their service. Cummins adjusted the parking brake and now it only rolls like an inch (or little less) on our driveway once I set the parking brake before 'locking' (if that is the term?), if even that.

Now, when I air up or dump air, movement is not even an inch. Of course I keep the rear wheels on the ground (or up on 2x12's when here at the house).

---> So, I'm not sure but perhaps getting the parking brake adjusted will limit that chassis movement on air up/air dump?


Apparently, according to other Spartan EC-2000 Series chassis owners, the parking brake is:

My diesel pusher (Spartan chassis, Cummins 5.9) has ONE spring brake drum on the drive shaft

Cummins told me that this type of parking brake is ancient technology when it comes to trucking, probably last used in the 80's if I remember what was told to me. Their tech's are familiar with it and know how to adjust it.


Want to note, this has nothing to do with the chassis jacks.


.

[CoachStreamr]

Originally Posted by AFChap

Just guessing, I would say mine moves forward 4-6 inches.

if you are on a slope and engage your parking brake, does your coach move the approx. same distance before stopping/parking?

[TLGPE]

Ray, I realize this thread is a little old, but just to clarify the subject of the coach rolling when the bags deflate, the coach moves BECAUSE the parking brake is locked. The rear suspension is built like a see-saw with the airbag pushing one end to lift the coach.

When the bag deflates, the angle of the see-saw changes, so the axle rotates a little. With the brake locked, the rotation of the axle also rotates the wheels, so you move forward. When the bags come back up, you move back.

It's possible that doing all that without the brakes locked would prevent this movement, but you need to be sure you are level. You could also put wheel chocks around the rear wheels to be sure. (But only if the brakes are released).

Of course, this has nothing to do with the original premise of storing the jacks before changing the air bags; that's a given.

TMI ? Sorry about that.

Tom

[Ray,IN]

Originally Posted by Dtwallace

I think there may be a misconception about auto dump.

My 2012MM will only start dumping air from the air springs once the leveling gear has lifted the chassis above the point where the leveling valve height is set. And this is the same for any air ride equipment I've ever owned or operated.

So if I don't manually dump the suspension air before I start my auto level, the jacks will start it's leveling at that set height of approximately 6-8 inches.

You will hear the leveling valves exhaust once the jacks take up the coaches weight because the suspension system no longer needs to.

Now what happens when I retract the leveling system, the suspension is still fully depleted (no air at all). The coach drops to the bottom stops, the leveling gear pad scrapping as the coach suspension system rocks forward due to it's geometry.

On the way up, the gear has cleared the ground, and all is quiet as the suspension system returns to normal ride height.

The advantage of us manually dumping the air from the suspension system before starting the leveling process is we end up with less height at the steps, and the front bumper has a few more inches of clearance in case you want to pull out the generator compartment.

As far as the scraping, It only goes away if I'm not on a hard surface (dirt lot), and the parking spot is level right from the start, it's a lot less noisy.

That's how mine works, now I'm sure there may be some systems that actually do dump air from the suspension before it starts the jack movement, but I would not want that type due to the increased possibility of damaging the entry step on say a 3" curb.

I have at times had to pay close attention to where my step was in relationship to the ground when parked, necessitating retracting the step prior to retracting the leveling system.

As far as I'm concerned, the way my system works is perfect for me, and DW. We get no surprises because we know exactly what its going to do.

DTW

My HWH system is one of those that operates differently than yours. I push the on button twice to activate auto mode, first air dumps, only after that action is completed does the system activate the hyd motor/pump. It will never begin to fill the air springs until the travel light is lit.

[PPCPilot]

Originally Posted by Stuart W

Thanks! Wow it really does move. Question, can I then roll back with air dumped? Then pull forward before bags pump up?

This post by Stuart brings another question to my mind. How many of you bother to deploy your jacks on your level concrete pad in your shed or garage space? Is there a benefit to storing the RV on the jacks vs on the tires/suspension?

Mine is parked in an outside storage lot and I have not been deploying the jacks there but I certainly could if there is a benefit to my coach. They used crushed bituminous for their parking lot and it seems to pack well with no dust.

On edit: I did not see that this post was so old! Did you discover that your coach moves Stuart when deploying your jacks?

[AFChap]

Originally Posted by PPCPilot

This post by Stuart brings another question to my mind. How many of you bother to deploy your jacks on your level concrete pad in your shed or garage space? Is there a benefit to storing the RV on the jacks vs on the tires/suspension?

I ALWAYS store my coach with jacks extended. This does take a good bit of weight off the tires and suspension, which certainly cannot hurt.

[samert111]

Originally Posted by AFChap

I ALWAYS store my coach with jacks extended. This does take a good bit of weight off the tires and suspension, which certainly cannot hurt.

I do the same.