ron.dittmer
North-East Illinois
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Joined: 02/26/2007
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IMO, the best place for a slide-out is BETWEEN the front a rear axles. A slide-out located well behind the rear axle is the absolute worst place. Think of the levereage, the down-forces a slide-out introduces. 500 pounds back there, subtracts 500 pounds in front of the rear axle, but the downforce can increase the load on the rear tires by piles more than 500 pounds. The weight from "leverage" is compounded.
I drew this up a few years ago to illustrate the situation with my own rig without a slide-out. On trips with a full tank of fresh water (that is located against the rear bumper) and us sitting in the front seats, the leverage from water-weight is so influential, that the measured weight on the front axle is only 100 pounds heavier during trips as compared to the rig completely empty. During trips, we load our rear axle to the rated limit as defined by Ford. Not carrying water changes the scenario significantly. We carry a full tank of fresh water because we exclusively boondock.
![[image]](https://live.staticflickr.com/65535/48533409317_fa166e2f85_z.jpg)
Adding a 500 pound slide-out located behind the rear axle on our particular rig would be detrimental.
More recently I made some suspension changes up front to address the harsh ride and rear-end sag. I replaced the heavy duty front springs with ones rated the next step down. This leveled the rig nicely and also makes the ride much better with reduced thrashing. You can read all about the project which includes pictures, by CLICKING HERE.
2007 Phoenix Cruiser model 2350, with 2006 Jeep Liberty in-tow
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Chum lee
Albuquerque, NM
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Joined: 08/03/2015
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Nice photo and overlays. They explain a lot, visually. It's important to understand that every pound you add behind the rear axle (especially at the rear of the motor home) widens the area you call "load on the rear axle" and narrows the area you call "load on the front axle."
I know it's an extreme case, but, think about this. If you added enough people standing on your rear bumper, at some point, you could actually lift the front wheels/axle off the ground through leverage. Front wheels without enough weight on them don't tend to steer or brake well, especially in rain and snow.
Motor home manufacturers are supposed to understand this when a vehicle is in the design phase, but, IMO, sometimes they clearly don't. What drives out the factory door isn't what the initial designers intended. They sell well though!
Chum lee
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pianotuna
Regina, SK, Canada
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Joined: 12/18/2004
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Chum lee,
That is why my front wheels are at 65 psi and the rear at 80 psi
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.
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pnichols
The Other California
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Joined: 04/26/2005
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Our 55 gallon fuel tank, 39 gallon FW tank, 39 gallon BW tank, 29 gallon GW tank, and 6 gallon hot water heater are all behind the rear axle of our 24 ft. E450-based Class C. HOWEVER, the heavy Onan genny and 18 gallon propane tank are way in the front right behind the cab area ... so I'm pretty sure that the Onan, the propane tank, the V10 engine, the transmission, the DW, and me all on their long lever arms to the rear axle ... are balancing things out!
I run about 75 PSI in the rear tires and about 65 PSI in the front tires. Even with all that weight in the rear, I still had to install Koni variable-rate shocks back there to reduce the pounding from the E450's relatively stiff rear leaf springs. (Many/most short Class C motorhomes are built on the E350 chassis.)
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2005 E450 Itasca 24V Class C
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pianotuna
Regina, SK, Canada
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pnichols,
All my tanks except fuel, are on the driver's side. Exception is propane just behind passenger side front wheel. The house batteries are also on the driver's side.
To try to compensate, I offset the generator from the middle to as far to the passenger's side as possible.
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Chum lee
Albuquerque, NM
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pianotuna wrote:Chum lee,
That is why my front wheels are at 65 psi and the rear at 80 psi
Hi Don. If those pressures soften the ride and improve the handling, I totally understand/appreciate that.
My ride: A 30' Class A F-53 178" wheelbase chassis (no slides) which is rated at 18,000 lbs. GVWR (11,000 rear and 7,000 front) with actual running weight of 16,560 lbs. It weighs approx. 10,360 rear and 6,200 front. This is fully loaded with all my stuff, +-70 gallons of fuel, +-20 gallons of propane, +-80 gallons of fresh water. The black/grey tanks empty. I like that. I run all my 19.5" tires at 90 psi. As an aging engineer and pilot, I like playing well below the established maximum limits. Years ago, I remember my Flight Instructor telling me, "There are old pilots, and there are bold pilots, but, there are no old bolt pilots." One of my favorite Engineering Professors also told me, "If you design a bridge that fails, it's best that you be on it, or, under it when it does. IMO, Stockton Rush is a recent perfect example of what they were talking about. DON'T OVERLOAD THINGS!
If you need a bigger motor home, buy one.
Chum lee
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pianotuna
Regina, SK, Canada
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Hi Chum lee,
Good advise. Overloading is playing Russian roulette.
My unit came with overloaded tires--but NOT overloaded axles.
I solved that by changing the wheels to a taller tire. The end result was that fully loaded I had 850 less than the maximum for the driver's rear axle. 14500 is the rating. That was with all tanks totally full and provisioned for a trip including 2 passengers. My no slides RV is 29'5". 176" E-450
It yielded 2 more inches in height, and improved the fuel mileage.
The reason for the lower pressure on the front tires was not for comfort--but rather for safe driving. At 80 psi it felt as if I were driving on a balloon. I had to keep correcting. I decided on 65 psi after weighing off front, back and each "corner".
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