Weight Creep

 I have covered the importance of knowing your actual RV weight, as that has a direct impact on your tire loading which affects your tire life.

The idea of "4 Corner Weight" is that you get on scales that can measure the load on each end of each axle because very few RVs have an exact 50/50 end to end load split for every axle.

 Now I know that finding a location that can measure each tire position is not easy. Large RV gatherings such as FMCA Conventions and Escapees meet-ups sometimes have vendors offering that service. HERE is some information from another tire engineer on where and how individual weights can be measured. Others have learned that their state scales as in Oregon and I believe Washington state are left "on" and they can many times get the weight of each  end of each axle on the scale so they can calculate the actual loading.

This is my RV on a scale in Oregon. The red circle is the weight sign.

Some folks have contacted their state police and found them more than willing to provide the service. HERE is a work sheet you can use when you get the scale readings..

One other consideration for every RV owner, even those that have not yet learned their corner weights. This is WEIGHT CREEP. This slow increase in overall weight occurs as we travel and add small items to our RV. This might be another tool or book or nick-knack. Individually they only may be a pound or two but over time the total weight can become significant.

Now, I am not saying you have to search out a company to re-do your 4-corner weights every year but you can get a handle on your weight creep with a quick visit to a regular truck scale where you can learn your individual axle weight. With that new information you can compare the total for each individual axle of your 4-corner weight with the new truck scale weight. Hopefully you will not see any significant weight gain that would require you to get new corner weights BUT you will at least know the facts and know if the extra "stuff" is adding up to a significant weight gain which suggests that you put the RV on a "diet".

 ##RVT967

"4-Corner" or CAT scale ?

Was reading a thread about scale weights on one of the RV forums.

OK Tireman9 here, an official card carrying member of the "Weight Police"

Seriously, some comments.

RE the Original Poster's  numbers. I would really be interested in learning the individual numbers from anyone who has done "4-corner" be it Escapees, RVSEF, on a closed State scale, State police portable or homemade scale.

The primary reason for 4-corner is not to get concerned about a 250# (5%) difference in individual tire position weight but to identify the outliers with 1,000# difference side to side which I am told is not that unusual.

I have posted several times both in my RV Tire blog and on various RV Forums that until you get confirmation with side to side weights that I suggest you assume a 53/47% side to side weight split. I have received scale numbers from a few folks and they were +/- 1% from the 53% figure for the heavy end of the axle. I have had 4-corner done 3 times (RVSEF and State Scale) and my Class-C runs at about 51.5% to 53.1% heavy for the heavy end of my 2 axles. I have also done a couple CAT scale readings just to ensure no significant "weight creep".

RE doing 4-corner on CAT. This is against CAT corporate policy as they say loading the platform way off-center can affect the scale accuracy and calibration. If you look around you will see that many CAT scales now have guard rail near the platforms to prevent off-center weights.

While I haven't looked at the Escapee scales, I have compared the RVSEF scales with some State Police scales and they appeared to be the same units.

The whole objective of getting tire weights is to avoid overloading your tires. No, your tires aren't likely to "blowout" if you have an extra 1% on one side vs the other, but if you discover you are at or above the load limit of your tires by 10% then you are really "consuming" the tire life faster than you might expect. This can result in a belt separation if you also push the speed rating for your tires in RV service (75 mph max).

Most folks never have belt separations on their cars but we all know that many RV owners have tire problems. One of the main reasons for this difference is that most cars are running around with 25% to 35% reserve load and are driving 20 to 40 mph below the tire speed rating for regular auto usage.

RVs, on the other hand, are running with 5% or - 10% reserve load and from 15 below to 15 mph above the speed rating for their tires when in RV service.

To address the calibration issues both with scales and pressure gauges. My Gauge tests find between 8% and 15%  are off by more than 5 psi with a few reading about 10 psi high which means that those owners were running their tires significantly underinflated.

All of this is why I suggest adding 10% to the minimum inflation required to support the load when you consult the tables after you use the heavy end of a 4 corner weight or the 53% figure from a CAT scale.