s.
Fortunately, the gross axle weight rating (GAWR) and the gross vehicle weight rating for the entire vehicle (GVWR) appear on the vehicle placard.
A quick aside: It is important that the cold inflation pressure for a motorhome tire never exceeds the maximum inflation pressure branded on the tire sidewall and/or the maximum load or inflation pressure stamped on the wheel.
Weighing In
The problem with weighing a motorhome or towable is that scales are not always easy to find. Unfortunately, that doesn’t let anyone off the hook.
For starters, all of the RV and major tiremaker Web sites have printable versions of how to weigh motorhomes and towables of every type imaginable.
You can print out these work sheets for your RV customers or they can print out their own copies. The bottom line here is that the customer must return a completed wheel weight position work sheet to you before you can do your job.
For the record, there are three types of scales: the platform, segmented platform or single axle. The platform scale is long enough to weigh the complete vehicle. The segmented platform scale can provide can provide individual axle weight and total vehicle weight simultaneously, while the single axle scale, as its name implies, weighs one axle at a time.
Regardless of scale type, the RV owner must be able to determine overall weight, the right and left side weights for each axle, and the weight on each individual axle from front to rear.
If a vehicle is in tow, the RV owner also needs to know what that vehicle weighs. This is the actual loaded weight of the RV plus the towed vehicle. Combined, they should not exceed the RV’s GCWR (gross combined weight rating).
Although GCWR has more to do with drivetrain design limits, this additional weight can also affect the tires and how the RV handles. Don’t forget to consider the tongue weight of the trailer and its impact on vehicle handling.
Everything Matters
Continuing with the weight issue, everything that goes into a motorhome or trailer adds weight. A few simple vacation purchases can change everything. We’ve heard about the couple from Rhode Island who bought stones out west for their rock garden back east. How much did those stones weigh and where were they stowed in the RV? One thing is absolute: As soon as those stones went into the RV, the total weight changed.
Everything must be weighed, including passengers, food, clothing, fuel, propane, water and supplies. Any towed vehicle (car/pickup/SUV, boat or trailer) or items loaded onto the vehicle (dirt bike, motorcycle, etc.) must also be included.
Helpful numbers to keep on hand:
Water ®“ 8.3 lbs. per gallon
Gasoline ®“ 5.6 lbs. per gallon
Diesel Fuel ®“ 6.8 lbs. per gallon
Propane ®“ 4.2 lbs. per gallon
Passengers ®“ About 150 lbs. each.
The average vacation-only RV’ing couple carries about 2,000 pounds (one ton) of belongings, while the average full-time RV’ing couple averages 3,000 pounds of personal belongings.
A few more words about towables. Most notable: tow ratings are furnished by the truck maker. You’ll find the tow rating for a pickup in the owner’s manual. For larger pickups, this is often based on the GVWR plus 2,000 pounds, engine size and axle ratio.
For smaller pickups, it’s based on chassis, drivetrain, engine size and axle ratio. Tow rating is also predicated on an optimum vehicle lifetime of 100,000 miles. The lesson here is to never exceed the tow vehicle’s recommended towing capacity or the trailer’s stated capacity.
Many towing truck owners mistakenly believe they can increase their truck’s GVWR rating by installing heavier springs, air bags and other suspension devices. In truth, these add-ons will only change ride quality and/or the truck’s attitude to the ground, not the GVWR.
If the towing vehicle weighs out at 7,000 pounds and has a GCWR of 10,000 pounds, the weight of the trailer (loaded) cannot exceed 3,000 pounds. Tongue weight should never exceed 10% to 15% of the gross trailer weight. Too much tongue weight will cause both the towing vehicle and trailer to sway, while too little tongue weight can cause severe trailer sway.
Caring For RV Tires
Finally, a few thoughts about RV tire care. When "blocking" the tires to level the vehicle, be sure that the block is larger than the footprint of the tire. No part of the tire should ever hang over the edge of the block. This can cause internal tire damage.
When storing a RV, tell your customers to put the vehicle up on blocks to take the load off the tires. Ideally, tires should be covered with opaque material to keep harmful UV rays away. Generally, dirt and grime does no damage to the tires, but washing them excessively removes protective compounds and can cause the tires to age prematurely.
The same is true of most tire dressings that make tires look shiny. Many of them remove protective compounds, again causing tires to age abnormally. Avoid harsh cleaning agents and steam cleaning, say the experts.
How long should a RV tire remain in service? Assuming there is no tire damage problem, most RV owners don’t replace tires by mileage. Instead, they replace tires when the warranty expires, or about every five years. According to several good sources, five years is reasonable lifetime for RV tires, again, assuming no other issues with the tire. However, tires that look old, have aging cracks in the sidewalls and shoulders, or have severe scuffing need to be replaced.
If the tires are to be stored off the RV, advise your customer to keep them in a cool, dry, dark place away from grease, oil or fuel, and well away from electrical equipment (like motors and generators) that produce ozone.
Tires should be stored inflated to a minimum pressure of 10 to 15 psi and arranged side by side. Avoid letting tires sit on asphalt for long periods of time because they can absorb damaging oils from the pavement.
Last, this word of advice. Make sure your RV customer understands that the lowest speed-rated tire on either the motorhome or towed car determines the maximum speed for the entire vehicle combination, including any towing vehicle. If they don’t, they could be asking for a real surprise.
