Answer Found.
Load Range
Load Range is another way of indicating the ability of a tire to handle stress and weight. This time, we are indicating how much load can be placed on the tire horizontally. Often, these tires are associated with towing because the back end of the car tends to wallow while towing a trailer. In other words, you are exerting stress on the tire from side-to-side.
While there is no industry-wide definition of ply rating, truck tires are frequently marked with ply rating and equivalent Load Range. These markings are used to identify the load and inflation limits of that particular tire, when used in a specific type of service:
Load Range Ply Rating
A 2
B 4
C 6
D 8
E 10
F 12
G 14
H 16
J 18
K 20
L 22
M 24
N 26
Source: Bridgestone/Firestone North America, Sizes and Classifications
Remember, load range indicates horizontal and sidewall strength.
What load rating and/or load range do I need?
Consider the following questions:
How far do I typically drive during the summer months?
Do I typically drive with my vehicle fully loaded?
How fast do I drive? (Interstate, high crosswinds)
What kind of vehicle do I have?
Do I tow a trailer?
Driving a heavy vehicle, fully loaded, during the summer, at high rates of speed puts much more stress on a tire than light-duty low-speed driving.
Light trucks such as the Volkswagen Vanagon have a fairly narrow track and a high center of gravity. The higher center of gravity tends to put more stress on tires due to body roll and load transfer. This kind of stress is exerted in a horizontal direction.
Volkswagen suggests a Load Range of C for its commercial vehicles (Bus, Vanagon, Eurovan). They do so because a 6-ply tire can withstand more side load and will not flex as much under these conditions.
[Most manufacturers do not offer 6-ply tires, nor do they document their load range.]
You should select the tire with the highest load rating and speed rating (and highest PSI) that you can afford that is in the size needed for your vehicle.
Lastly, while a Vanagon Westfalia has a higher center of gravity, and possibly more weight at the top of the vehicle, other models are lower and do not carry weight above the mid-section of the vehicle. The lower the weight is, the less force will be transferred from side to side when cornering or in heavy cross-winds.