The level of accuracy depends on the application. Generally Â±0.5 to 1C accuracy is sufficient in the food industry whereas the pharmaceutical industry may require Â±0.2 to 0.5C accuracy or better. It is important to note the scale used in comparisons though Â±0.2C accuracy is not the same as Â±0.2F accuracy.
All vehicles towing trailers must have chains on one drive axle. Trailers with brakes must have chains on at least one axle. Requirement 2 (R-2): Chains are required on all vehicles except four-wheel-drive vehicles under 6,500 pounds gross weight and equipped with snow tires on all four wheels. Chains for one set of drive wheels must be carried by four wheel-drive vehicles using snow tires. Requirement 3 (R-3): Chains are required on all vehicles without exception. R-1 and R-2 are the most common conditions.
For rear-wheel-drive vehicles, the chains should be applied to the rear wheels. Some trucks and extreme conditions may call for tire chains on all wheels, which is fine, but make sure you put the chains on the right tires when you only have two.