RV Repair Manual
for the RV Do-It-Yourselfer
Do you know that there is a difference between passenger vehicle tires and camper tires & RV tires? If not, don't feel bad. Most people aren't aware that there is a difference either. This article will help you to learn the difference and make sure you are using the correct tires for your RV or camper.
When looking at the two different kinds of tires, you might not be able to visually tell that they are different but there is a significant difference between them. Passenger vehicle tires are designed for traction and handling over different road surfaces. Camper tires are designed for strength to support the weight of the camper and its contents and to handle the stresses of cornering and backing.
Camper and trailer tires are stamped with "ST" on the sidewall. The 'Special Trailer' (ST) tires are constructed for better high speed durability, extended towing time and damage resistance under heavy loads. Trailer tire construction varies quite a bit from automotive tires, for that reason, it is important to choose the correct tire for your towing application. In general, trailer tires have the same load range (or ply) from bead to bead and are bias ply construction. This type of construction allows for a stiffer side wall which provides safer towing by reducing trailer sway problems. The use of 'Passenger Car' (P) or 'Light Truck (LT) tires a on a RV, camper or trailer is not recommended because their construction. They are usually radial or bias belted, making for a more flexible side wall which could lead to increased trailer sway and loss of control.
Passenger vehicle tires usually determine their condition by the amount of tread depth they have. Since trailer tires are developed with a stronger sidewall and because campers don't get used as much as our passenger vehicles, the tread doesn't normally wear out as quickly so sidewall condition needs to be checked for all campers and trailers. Most trailer tires have a life span of 3-5 years but that can be significantly extended if the tires are treated with a tire treatment and covered when not in use. By treating the tires with a tire conditioner, it helps to keep the rubber supple thus avoiding dry rot. If you can use tire covers, it helps to prevent premature aging due to UV rays and weather condition.
When replacing your trailer tires and trailer rims it is critical that the proper size and load range be selected in order to match the load requirements of the camper trailer. The following characteristics are should be checked when replacing trailer tires.
TIRE CONSTRUCTION - Bias Ply or. Radial
TIRE APPLICATION TYPE - (ST) Special Trailer or (P) Passenger Car
TIRE LOAD RANGE - Load carrying capacity & air pressure rating
RIM SIZE - Diameter and width must match tire
RIM BOLT CIRCLE - Diameter of bolt circle must match hub
Many people are uncertain how to read the specifications on a tire side wall. The metric system is the most common measurement system used for tire sizes. Below is an example and explanation of the metric tire code.
THE METRIC SYSTEM - (ST205 75D 15)
Tire application type (ST-special trailer)
Section width (205mm)
'Aspect Ratio' (75)
Construction type (D= bias ply)
Rim diameter (15")
You will also want to be sure to buy tires that have been designed to carry the weight of your fully loaded camper. The weight of your fully loaded camper is the GVWR (gross vehicle weight rating) of the camper. Tires are stamped with a rating, called a Tire 'load range'. This is the maximum weight each tire can safely support. It must be considered when selecting the proper size tire. The load range and maximum weight capacity are indicated on the tire side wall with a letter which is usually between B and D. The higher letters designate that they can support more weight. This rating is used in conjunction with weights the axles can support. A higher rated for tire will not necessarily mean the camper can hold added weight.
LOAD RANGE B = OLD 4 PLY RATING
LOAD RANGE C = OLD 6 PLY RATING
LOAD RANGE D = OLD 8 PLY RATING
To tell the age of the tire, look for a four digit number following the DOT serial number. This is typically found on the back of the tire. The date code will be stamped in an oval shape. The first two digits are the week of the year in which the tire was manufactured (01 thru 52) followed by the last two digits, which signify the year that it was manufactured. A tire stamped "2009" was manufactured in the 20th week of 2009.
Tire inflation pressure is another critical factor in the proper handling as well as the life of the tire. Maximum inflation pressure is stamped on the side wall of the tire and should always be checked when the tire is cold. "Cold" refers to the temperature of the tire before being towed, not to the exterior atmospheric temperature. Tire pressure should be checked on a regular basis to ensure that there are no leaks or damage to the tires.
This information is provided to help to assist you with the correct choice and safe operation of your RV, camper and trailers. RV tires are not typically balanced by the factory. This could lead to tire failure. It is recommended that you have the tires professionally mounted and balanced.
Visit my website at http://www.allaboutcampers.com for more information about campers, camper trailers and RVs.