Chassis Ramblin’s
By Brad Sears
Well it is Sunday here in rural New Hampshire, 23 degrees outside and an ice storm rolling in tonight. This coming Wednesday we were supposed to be pointing the old Fortravel’s nose south, but plans have changed. The old guy, me, got slammed with bronchial pneumonia, so we will not be heading south, nor will I be going anywhere soon.
So what to do on a Sunday afternoon? Watch the Daytona 500 on TV, thats what. Ya, so what you ask? Well it has to do with what I have been writing in my blogs the past several weeks, chassis handling.
In looking over what is on the market to try to eliminate some of the lousy handling that we have in motor homes, it is amazing at the number of products that are sold for the front end of the vehicle as opposed treating the rear of the rig.
However it is a known fact that the rear overhang as compared to the total length of the rig has a lot to do with tail wag and handling. It is a fact that NASCAR mechanics appear to think that when solving a drivers handling complaints that making adjustments to the rear of the car is where it is at.
After last weeks blog several folks indicated that adding supplemental air bags to the rig was the the best investment that they had made for their coach. When I thought about this for a minute, I had to agree.
Being a gear head and a teacher, I could not just put air in the new air bags on the back of my 33 foot Southwind on a P-30 chassis, I had to play and keep notes. I played with air pressures and measured chassis height for each pressure. I played with this chassis for over a year trying to make it behave. It was built during the national 55 mile per hour speed limit and at 55 it did not handle too bad. But over that? Another story.
I soon came to the conclusion that all weight distribution was not created equal and that I had to run more air pressure in the right rear bag than the left side. The reason is simple when you think of it. All roads are engineered with a crown to allow for water to run off to the side. With a lot of overhang and a bunch of weight in the overhang as the coach tips to the right the effect is like a bunch of weight hanging on a rope and will try to pull the tail off to the right and down.
This action will tend to lift the weight off the left front wheel and upset the camber and caster.
the 500 is over and as usual the television pundants were all wet. They had worked for weeks setting up this wonderful match up between the Hendrick’s team and the Gibb’s crew matching Chevrolet and Toyota. When it was all over the Captain, Roger Penske and his merry band, driving Dodges snuck in to steal the apple pie off the window sill. One two finish with Newman and Bush as top dogs.
Stay tuned for more stuff next week.
Brad Sears
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William A Harland
Im very new at this camping thing, We just brought a Sunline Solaris 24′ 5″ never pulled a camper this size before and there shure is a lot to learn about weight distributing with a camper this size behind my Ford f-150 pickup. A lot that you said if very confusing to me being new at this, we wont to travel over the country with the camper and i’m a little bit afraid of not having the camper loaded right, Your information was very hepfull, There shure is a loot to know about towing a camper this size. I hate the idea about what the 18 wheelers do to the camper when they pass you on the interstate, There is so much information out there i just cant asorb it all,I guest im just going to have to get behind the weel and try the experience to see what the feeling is.Hope that i dont crash up the new camper or cause any injuries to any one. Thanks for all the helpfull information. William A Harland Woodsville New Hampshire
curt
Brad-I looked at a 5th wheel yesterday that had all the wt. on the street side! 21′ Ref, lp tanks, 4 Bat, wash/dryer, all kitchen/pantry, THIS added to the highway slant must be a nightmare when going around a right curve? Any concerns with balance in the 36-38′ 5th wheels.
Mark Polk
Brad,
Good point about the rear of the motorhome being the culprit in many cases. When we bought our new 35’ gas motorhome in 2006 I noticed what I referred to as the “push-pull effect” the first time a semi passed us on the Interstate. Some people call it sway or body roll. Whatever you call it, as the truck is passing you, the first thing you feel is the air pressure from the truck pushing against the side of the motorhome. Then as the truck starts to go past the motorhome it pulls you back in. This sensation make the motorhome feel top heavy.
You will experience these different types of sway whenever pressure is exerted against one side of the motorhome. It can be caused by a gust of wind, or possibly a shift in weight while cornering. The effects of sway on a motorhome are increased because of the height and mass of the motorhome. Over time it takes its toll on the driver.
Many times the solution to the problem is in the rear suspension. Chassis manufacturers are aware of this problem and use what is referred to as a sway bar. The sway bar is the direct link between the suspension system and the vehicles frame. The sway bar uses the weight of the rear axle as a brace against the chassis, so any pressure exerted against either side of the motorhome is countered by the sway bar. The problem with this, in many cases, is the stock sway bar is not strong enough to absorb or counter the effects of sway or pressure exerted against the sides of the motorhome.
I bought an RSS sway bar and installed it on the motorhome. It’s a thicker diameter bar than stock sway bars and does a good job improving the handling and reducing the push-pull effect.
Mark Polk