Recently I have had more questions about wind drag than any other. Hopefully I will be able to address all your concerns in the next few hundred words. Remember, everything I know has been learned from my time on the road.
First let's discuss what gear ratio you are using or wish you were using. Gears come with different ratios -- some allow greater fuel efficiency and others more power.
How many miles you are traveling with a full load in your RV should be a important factor in your choice. The amount of power at the drive wheels is called torque, and horsepower is required to produce it. A 1-to-1 axle ratio represents a turn of the drive wheel for every revolution of the drive shaft. The higher the number, the lower the gear ratio. This means a 4-to-1 is producing power vs. economy. When towing I would rather err toward too much power than too little. Too little power means failure at some point on the road. None of us want that.
If you are pulling more than a 7,500-lb. load, it is necessary to use a 4-to-1 gear ratio. When purchasing an RV or a truck, DO NOT DEPEND ON THE SALESPERSON TO GIVE YOU THE CORRECT INFO ON THIS! Take the initiative and look in the manufacturer's manual. Even RV companies that build sub-standard units tend to have the correct info in the manual when it comes to what should be used under whatever weight you are considering pulling.
Once the gears have been picked out, it is time to balance the load. This is really important when pulling a trailer. If there is too much weight on the hitch, it could lift the front wheels. RVs should travel with the weight evenly balanced. This will keep from rocking over bumps. Many people complain about drag when actually the RV is so out of balance it is dangerous to drive it down the road. I think this is the mistake that RV owners make most often. Really take time to even out the weight added by all your "stuff." This will save in so many ways while traveling.
For towing ease I think a four-way hitch is best. It pivots and makes trips on backroads a dream. The heavier the load, the more important the need for a four-way hitch. Speaking of the hitch, the pin weight needs to be addressed next. Pin weight is pressure coming down on the bed of the pick-up while its towing the 5th wheel.
The ">suspension should be able to handle up to 35% of the gross vehicle weight for trailers. It bears checking out, but some trailer suspensions can handle barely more than half that amount of pin weight.
I did not know this prior to the Harrisburg show, but most trailers do not come equipped with shock absorbers. Put some on. Electrical goodies will last much longer, and it will make a drastic difference on how the RV goes down the road.
Remember the shorter the wheelbase, the harder the drive. The combination of a short wheelbase and a tandem axle is very difficult when it comes to handling. If you need the tandem axle, trade off by making the wheelbase as long as possible.
Speaking of wheels, make sure they are aligned properly. This can be tricky with trucks and trailers because many trailers have axles that are far too light duty for what is being asked of them. Have this done by someone who works with trucks. The cheap tire-and-go shops or department-store-type tire stores rarely handle this problem and are not able to correctly line up the load.
Most of the problems that RV'ers have with drag are really the problems I have listed here. If I have not addressed your particular problem, let me know and I will do my best to find a solution. I have finished a test drive of the Phoenix Class B motorhome. I hope you enjoy reading it as much as I did taking it.
