Page 4 - Travelor - Summer 2016 - Issue 34

Page 4 - DRVC Travelore
RV
Tire
Basics,
Age & Air
Pressure
by Dick Lorntson
LOAD RATING
Each tire has a load rating. It relates to the number of
plies in the tread support system. This information may appear on the tire as “LRG” meaning “Load Range G”. Load range G = 14 ply rating. Different load range letters relate directly to the ply thickness of the tire, and as such, the carrying capacity of that tire.
MAXIMUM AIR PRESSURE
Each tire has an acceptable maximum air pressure rating. This marking indicates the maximum amount of pres- sure that the tire is able to handle. Minimum air pressure is listed in the charts. Don’t ever exceed the maximum air pressure on the tire or the wheel on which your tire is mounted.
SPEED RATING
Most RV tires are speed rated to 75MPH – exceed this speed and your carrying capacity drops proportionally.
TIRE SIZE
Tire size is likely the easiest marking to find on your tire. Common sizes include:
245/70R19.5 (245mm width, 70 percent height versus width, R = Radial construction, 19.5 = diameter of wheel), 235/80R22.5, 275/80R22.5, and 225/70R19.5.
THE TIRE PRESSURE QUESTION
Now, the million-dollar question is “how much air pressure should I run in the tires on my RV?” The answer is: “Until you know the four corner weights of your RV, you do not really know.” Knowing the precise weight of each corner independent of the others is the only accurate method of determining the proper air pressure for your specific RV. Different RV’s carry different weights, are packed differ- ently, weight is distributed differently, and may not have the same tires on them. The placard with air pressure recommendations, found somewhere inside your coach, is generic at best. The coachbuilders and their engineers have no idea exactly what tires you may have mounted, (you
are maybe on your second or third set of tires) or how and where in the coach you will carry your weight (treasures and what-ifs).
To weigh your motorhome correctly, measure the fully loaded vehicle (full of fuel and with the normal amount of water and LP that you usually carry) using independent
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Understanding and monitoring tire age and pressure may be the most important area of your motor home when it comes to safety. It is also one of the least expensive “fixes” any owner can do to improve ride and handling.
There are several markings on the sidewall of a tire that you should be aware of. The list includes manufacture date, load rating, air pressure range, speed rating, and size. You will find these on all RV and passenger tires sold in the US.
MANUFACTURE DATE
Knowing the actual age of your tires is important because most RV tires do not fail because of tire wear; rather they suffer damage from extended periods of neglect and inac- tivity. All tires have a
DOT number on them, usually on only one side. This begins with the letters “DOT” and indicates that the tire meets all U.S. federal standards. The next two numbers or letters are the plant code where it was manufactured, and the last three or four numbers, grouped together, repre- sent the week and year the tire was built. For example, the numbers 317 means the 31st week of 1997 and as such
1204 would be the 12th week of 2004. The other numbers are marketing codes used and manufacturer codes for reference should a recall be issued. Tires over five years old should be inspected annually by a certified tire dealer and all tires over seven years old should be replaced regardless of the miles or remaining tread.