Weight Distribution and Optimized Tire Pressures

Now here is a subject that raises the hair of my students at my RV maintenance classes. Shouting matches and blood veins popping on foreheads is normal when this subject is discussed. There is a lot of confusion , most of which comes from frustration in weighing the motorhome and the procedure for determining the optimum tire pressure. Another problem is the recommendations for tire pressures on the Ford F53 chassis as the harsh ride can be somewhat reduced by lowering the tire pressures. I have seen recommendations as low as 73 lbs. which may help some to reduce harshness but will risk reduced tire life.

I have made a decision to develop a class where this is the only topic discussed. I have researched and found only one other class available on the internet and it was recorded about 10 years ago and the lecturer blamed weight distribution for many of the safety problems and related tire problems happening at that time before better and RV specific radial tires were developed.

Back when I first studied suspensions ( on race vehicles ), the rule was wide wheel base and the lowest center of gravity possible. The karts I was racing, had the driver about two inches off the ground so not much chance of flipping over unless assisted.

Your motorhome is a unique situation, since the width between front tires and between rear tires is regulated because of highway lane width. Front to back wheelbase is very long, so if a motor home tips over you can be assured that it will be on one of the sides not the front or rear shell - physics. I saw the result of a large class C motorhome tipped over on its side in eastern Washington just off the Interstate. It looked brand new and the saddest scene was the two occupants sitting outside being consoled by a EMS person. It scared me.

The key to safety and handling on a motorhome or a race car is keeping all 4 wheels on the ground. The best starting point is equal weight distribution side to side. Weighing the motorhome at all four wheels will reveal any side to side weight problems. The next problem is what can you do about it. Shifting items stored in any storage area may help. Moving lighter items to the heavier side and heavier items to the lighter but this can a frustrating exercise. The fresh water tank is usually on one side and is pretty big so only fill to minimum need levels for trips and then fill the tank just before entering the boondock location. This may help or it may make it worse. The black and grey water tanks straddle the width of the motorhome so as they fill the weight should be equally distributed, but what about when you turn at speed - the fluids shift . So travel with empty tanks, but what about the fuel tank, it starts out full and loses weight until time for a fuel up.

How do race cars handle weight distribution at very high speeds? They jack up one side to shift weight to the other. The target weight distribution for the motorhome at rest is equal weight on the two front tires and equal weight on the two sets of rear duals. The front axle would have about one third of the total weight and the rear axle the remaining two thirds. But this is impossible as discussed above - UNTIL NOW! When I start my motorhome to leave the RV park, I first move the slides in and then stow the leveling jacks. The next step is to turn on my LiquidSpring smart suspension. Immediately the suspension begins moving to equalize weights side to side and 1/3 to2/3 front to rear and it will continue to maintain this weight distribution for the entire trip even when turning, even when fuel burns off, and even when my wife gets up and turns off the dishwasher and then goes to the 1/2 bathroom. THIS is the GIANT step forward that the 4Corner smart suspension makes to the safety and handling performance of the motorhome - its dynamic- its beautiful. Now we can determine accurately the optimum tire pressure recommended by the tire engineer for the optimum gas mileage, handling ,safety, and longest tire life - not just at rest but on the road, dynamically controlled for optimum results.

No more compromises - optimized. The next part of RV weight distribution will be thoughts of how aerodynamics or lack of it has a role in weight distribution and also exactly how does a smart suspension change weight distribution.