Difference Between SFI 16.1 & 16.5

By Dani Clark

At the starting line, most race car drivers are probably thinking more about winning rather than their safety restraints. Still, it is of extreme importance that drivers use quality safety belts to keep injuries to a minimum in case an accident occurs before reaching the finish line. The SFI Foundation, Inc. is one organization that sets specification standards for various types of safety equipment, including driver restraint and stock car driver restraint assemblies.

Functions and Quality

Seat belt restraints have several parts with different functions. There is a harness for the shoulders to minimize movement of the upper body and shoulder areas. Some manufacturers will include an additional chest strap that attaches each shoulder strap together. The pelvic area is contained by two separate straps, the lap belt and the anti-submarine strap. The buckle keeps the belts connected, and the driver should be able to release in one to two moves. Aside from adjustment capabilities, the seat belt restraint needs to be properly installed to guarantee the highest safety possible.

While there are a variety of harnesses available to consumers, all seat belts are not created equal. These belts may all look similar in form, but all may not meet SFI's stringent specifications. Manufacturers can choose to participate in the SFI testing program, and products that pass will have printed proof of the product's quality.

SFI 16.1

The 16.1 standard is strictly for driver restraint assemblies. The specifications detail accepted fabrics, design styles, proportions, requirements, and testing methods. There are three different classes of belts, based on the width of different belt straps within the total belt assembly. Belt webbing must be able to withstand certain weight loads within their classes. According to the 2006 release specifications, minimum weight loads range from 6,200 to 8,000 lbs.

SFI 16.5

The 16.5 standard is for stock car driver restraint assemblies and is the NASCAR requirement. Again, the specifications list requirements for items ranging from fabrics to testing methods. According to the 2007 specification updates, webbing width must be at least 1.72 inches, and the minimum breaking strength for all belt webbing must be 7,000 lbs. Furthermore, in the body block test, the total load belts can withstand should be at least 11,500 lbs.


Exposure to sunlight causes belt fibers to weaken, so the lifespan of restraints meeting either the 16.1 or 16.5 specifications is only two years. Restraints must be replaced at this time, or the original manufacturer will have to re-web the belt assembly and have it recertified. Should drivers continue to use old belts, the outcome could be tragic.

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