Handling: Rocking and Rolling: UPDATE

[Snowman9000]

Our Sunseeker 2300 Chevy sure pitches side to side a lot when we encounter any bumps at all while turning at slow speed, such as leaving a parking lot. I have to go pretty slow, otherwise stuff will be flying.

It has sway bars, but would stouter ones help enough to matter? What else would stouter sway bars do to the handling and ride?

I have rear air bags, set to about the middle of their psi range. I have not experimented with them.

[burlmart]

Be nice if you knew a shop dedicated to servicing U=Haul trucks and talk w/ their Chevy suspension know-it-all.

[Gene_in_NE]

Snowman9000 wrote:
Our Sunseeker 2300 Chevy sure pitches side to side a lot when we encounter any bumps at all while turning at slow speed, such as leaving a parking lot....

As others have stated, the difference in height can make a difference in rocking side to side. That A/C on top is about 7" higher than on your previous motorhome. A 2005 RVision Trail-Lite 213 was 10'-8" while the 2014 Forest River Sunseeker 2300 is 11'-3". You also have a much heavier looking cab-over. I'm fairly certain that your Trail-Lite gas tank was lengthwise and between the axles and so was your fresh water tank.

Handbasket probably has the best suggestion of varying the air pressure in your air bag. I would start by dropping the pressure from 50 to 40, then 30...until 10 psig. I doubt you need to be above 50 as that 4500 should have enough spring to hold your weight.

[ron_dittmer]

Beefier sway bars will also benefit in parking lot dips as well as on the open road. As j-d stated, they will also stabilize the rig when parked. People walking around inside will have less effective motion on the vehicle.

Everyone can easily experiment on their own motor home's rear sway bar very simply (and fun) to determine effectiveness. Have a few family members stand together inside the motor home over the rear axle, all members facing forward. Have them work together trying their best to rock the rig side to side by shifting their weight left to right in unison. An effective rear sway bar will lower both rear corners simultaneously regardless which way the weight has shifted. If you had no rear sway bar, one corner would raise up when the other rear corner went down. You can sight it best looking at the relationship between the rear tire and RV body.

A lesser rear sway bar will lower both rear corners, but not as much as a heavy duty bar would, hence you will still feel the rig rocking.

You could also perform this experiment on the front axle but because people can't stand directly over the front axle, you might not be able to get enough rocking motion to see the results. Still it would be worth a try.

When I perform this experiment on the rear of my own rig with Roadmaster heavy duty sway bars, I feel the entire rear of the motor home drop regardless of how I shifted my weight. I simply cannot get the rig to rock side to side. It gets cancelled out by dropping the entire rear of the rig by some amount.

[Its_Hondo]

Interesting discussion....

My 23 foot Jamboree has airbags, a single fill point & air pressure gauge on the trailer hitch. I can understand how having each side linked via common tubing might contribute to racking & pressure transfer. I may separate the lines & see how it goes.

You can see how the previous owner mounted it here-



Previous owner said he kept the pressure at 50 psi and that is where I have kept it. The ride in the rear is pretty harsh though so I'm going to experiment with different pressures.

[RvBill3]

ron.dittmer wrote:

You are the first person in the 7 years I've been on this forum who mentioned a sway problem on their Chevy chassis. Either you have a unique problem or nobody else with a Chevy wants to discuss it.

I don't consider my Chevy to have a sway problem. Some minor rocking at the slow speed driveway type movement that Snowman is talking about, but nothing that concerns me. I've been following this thread to see if I'm doing anything different. I do travel with a full fresh water tank most of the time, and generally start trips with full fuel and refuel at about 1/2 tank. Holding tanks mostly empty. I usually start air bags at 60 psi. Add a little air if I know we are going to be facing strong cross winds.

Maybe the shifting of partially full tanks is the difference. Maybe the air bags need a little more air.

[Snowman9000]

Ron, it's not sway going down the road, from wind and trucks etc. It handles pretty well on the road. It's rocking like a boat when something bumps the back end up or down while traveling at parking lot speed. That still might be fixed by a sway bar. The rear bar looked like it is ~1 & 3/8ths. Don't recall the bushings. Probably rubber.

jd, the tanks are crossways. It is something I'm going to be paying attention to, although the way we travel, water will be present.

[j-d]

Your gasoline tank, furnished by Chevrolet, may be baffled inside. Even if not, it's probably installed lengthwise in the chassis, so gasoline shifted side to side doesn't have all that far to "slosh." Are your water tanks (fresh, gray, black) installed crosswise under the coach body?
This may sound counterintuitive, but a warship with a damaged, partially flooded compartment will often choose to flood it fully. The partially filled compartment is more de-stabilizing than it would be fully flooded despite the additional weight. It's called "Free Surface Effect." If you had three tanks, each half full, mounted crosswise, I think you might feel the surge of the combined weight of the water.

[ron_dittmer]

Snowman 9000,

Of coarse you'll want your rig to handle properly when you are loaded up on vacation with your precious cargo, rather than running around town empty. You are on-track to get it figured out.

If you conclude that you need to take next steps, J-D was "On The Money" with his inputs I included below. You know so well that he and I support the use of heavy duty sway bars on our Fords. We are assuming the Chevy will benefit the same. I am not sure Hellwig and Roadmaster sell heavy duty sway bars for the Chevy/GM chassis. I also wonder how the stock Chevy front & rear sway bars compare dimensionally and bushing type, rubber or polymer.

You are the first person in the 7 years I've been on this forum who mentioned a sway problem on their Chevy chassis. Either you have a unique problem or nobody else with a Chevy wants to discuss it.

j-d wrote:
We replaced our skinny OEM sway bars with much larger Hellwig bars and the changes were only for the better. In theory there can be "too much sway bar" but I believe it pertains to cars and racing, and there is no practical limit for motorhomes. Being as they are very high, making them topheavy, and not driven to extremes.
Does it sway when parked on a campsite and people are moving around? You'll always feel movement in a Class C but if it wallows like it's driving on the road, stiffer sway bars will help greatly.

[Snowman9000]

Ichabod, the thing I thought about the airbags is that maybe they are a way to give the 4500 a soft-enough ride on the smaller MHs. Put slightly soft springs on, and then let the owner stiffen it up to suit with the bags. Because, it does ride nice when empty, for a small rig on a 4500 chassis.

Your report is encouraging. Is there more than one Bilstein model for these? EDIT: I checked and even called Bilstein. They do not make a shock for the current 4500's. 😞

[IAMICHABOD]

I think you are on the right path, as you said your old rig was shorter and lower to the ground. This one is taller and with the higher center of gravity and added fuel and water placement behind and above the axel they will tend to sway more.

Mine on a Chevy chassis did the same somewhat, getting that boat rocking, back in forth, back in forth motion. After I changed out the OEM shocks to Bilsteins It only makes one slight roll then returns to center, It seemed to be a better damping effect in the side to side roll. They really helped in that and the porpoising effect. I also do not have any airbags, but mine is small and I don't tow so I have no use for them.
They would seem to be overkill on a small rig where the axel weights and GVWR are well under the max limits as mine are.

Good luck in finding a solution, I hope that this may be of help.

[Snowman9000]

I went out for a test drive with all water and fuel empty.
It was a lot better on those bumps during turns. It did not pitch back and forth like a boat. Well, not nearly as much as when fully loaded.

Then I filled up the gas tank, it took 49 gallons. It still handled bumps in turns quite well. I also drove around in three different potholed gravel parking lots, and it was okay. Much better than when fully loaded. In addition, the ride quality going down the road was much better today. I took it down several miles of state highway with a lot of joints and such; that normally would have felt pretty rough, and today it was not bad.

So my guess is that when it is loaded, it is under-sprung and/or under-dampened. I'll start by adding air to the bags. Might be a few months before we have it loaded up again though. Anyone else's thoughts welcome, too.

[Snowman9000]

To answer some of the comments and questions...

I'm not talking about the obvious sloped entrances of the tail dragging kind. I'm just talking about any irregularity encountered on a slow speed turn. Just turn out of a flat parking lot onto a street. There is usually some flat bump there of some sort. Either patched potholes, or a depressed (flat) curb, or a very mild change of slope, or whatever. Same goes on turns in town at intersections. Any little thing seems to cause a lot of pitching. In a car, you or I wouldn't even think twice about them, wouldn't even notice them. We'd just drive right around the turn. In this MH, I have to go quite slow, just about crawling.

It's a brand new 2014, small MH but on a Chevy 4500.
I don't know for sure if it does it on both axles but I think it's mostly on the rear.
I feel we've done a good job of packing for weight distribution. One wildcard would be water in the fresh and wastewater tanks. We tend to always be carrying some flavor of water in fair amounts. And they are behind the axle, and above it, in heated compartments. That very well could be contributing. It's all empty now, so maybe I'll take it around town and check that out today. Even the gas tank is empty (also behind the axle).
We previously had a 23' B+ on a Chevy 3500 with no air bags. It was both lower to the ground and lower profile overall. It was not as bad.

Even if it is the water and gas, I'd still be willing to spend some money to improve it. If for example a sway bar upgrade would make a good difference.

Finally, I can live with it easily. It's not a big complaint. It's more that we hope to keep this MH for a while and drive it a lot, so I'm motivated to make it better. Just like anyone might do with their favorite car or truck for example.

[Handbasket]

I'd definitely agree with experimenting with the air bag pressures. Try 10 psi steps, lower first. Remember that there's a lowest pressure that's necessary to prevent damage by chaffing. Probably 10 psi, but it should be in the owner's info sheet or web site.

Good luck with it.

Jim, "Mo' coffee!"

[RvBill3]

Snowman9000 wrote:
Our Sunseeker 2300 Chevy sure pitches side to side a lot when we encounter any bumps at all while turning at slow speed, such as leaving a parking lot. I have to go pretty slow, otherwise stuff will be flying.

It has sway bars, but would stouter ones help enough to matter? What else would stouter sway bars do to the handling and ride?

I have rear air bags, set to about the middle of their psi range. I have not experimented with them.

I think what you are describing is pretty normal. You can lower air in air bags a little and see if that helps, but if I had to choose handling on road vs. pulling out of driveways, I'll set air bags for the road every time.

I use to drive a sports car that required taking transitions very slow so as not to drag bottom. It just became second nature. I think you will find that to be so with the MH after awhile. I would not spend money on new equipment until you try different settings on air bags and "just get used to it".