Other than the armor, tires are the most important part of an armored vehicle. Tires are one of the very few components the driver can easily modify that will produce substantial changes to the vehicle’s performance and safety. My experience tells me that most problems with armored vehicles start with the tires (Specifically the front tires) not able to handle the vehicle’s additional weight.
BASICS
The amount of weight the tire can support depends on the air in the tire. The more air in the tire the more weight the tire can support. Stamped on the sidewall of all tires is the amount of air combined with the weight the tire can support. The stamping will give a tire pressure number at a particular weight. Such as a “45 psi at 1450 Lbs”, the tire company is telling you that if you have 1450Lbs on that tire you must have 45 psi in the tire. Tire pressure can be measured with a tire pressure gauge, but how is the weight on the tire determined -that’s the job of the armorer.
MANUFACTURERS RESPONSIBILITY
The armorer needs to weigh the vehicle to determine the weight on each tire, considering the cost of the armored vehicle this is not asking for much.
The static weight (the car motionless) on each tire is good to know, it is only a starting point. A vehicle is a weight transfer machine. When the brakes are applied and/or the steering wheel is turned weight is transferred side to side and/or back to front. This applies additional weight to the tires, and specifically to the front tires.
Since most vehicles have more weight on the front tires than on the rear, the front tires need the attention. The additional weight on the front tires from weight transfer is a function of wheelbase and Center of Gravity height and needs to be measured. The armorer should give you the weight on the front tires static and when the load is transferred under hard braking. This requires some high school math and a $400 G Meter. Again, for what you pay for the vehicle I don’t think it is too much to ask.
Explanation of Tire Load
A tire with the designation of P195/60R15 87S – The load index (87) is the tire size’s assigned numerical value used to compare relative load carrying capabilities. In the case of our example, the 87 identifies the tires ability to carry approximately 1,201 pounds.
The higher the tire’s load index number, the greater its load carrying capacity.
Suggestions
Don’t ask; demand that the manufacturer measures the weight on each tire – before and after armoring.
Ask for the additional weight on the front tires due to weight transfer under braking.
The additional weight on each tire has to be addressed by the manufacture.
Constant measuring of tire pressures is suggested – especially in environments that have poor road conditions.
As a reminder – low tire pressure plus weight combined with weight above the center of gravity is a major problem