How two-inch racing harnesses bucked the system

Image by Jason Isley

How two-inch racing harnesses bucked the system

SCCA / SportsCar Magazine

How two-inch racing harnesses bucked the system

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No matter which SCCA venue you choose to have fun with your car, some kind of seatbelt is required. For SCCA road racing or pro racing there are no options: a multi-point racing harness is a must.

But, while aftermarket belt requirements in SCCA’s rulebooks have not changed much over the years, the specifics contained within those general requirements certainly have.

So why have the specs for harnesses changed? By and large, it’s because of the proliferation of head and neck restraints. These days, you simply can’t road race without one.

“All of our specifications were changed,” Carl Olson, motorsports manager at the SFI Foundation, says of the harness belt-width rules. “16.1, 16.5, and 16.6 were all revised to allow for whatever width of webbing meets the specification – a lab-performance specification.”

However, it’s not just head and neck restraints. Many factors came together recently to effect change in the harness industry.

“Narrow lap belts and shoulder harnesses were part of a comprehensive bio-physical examination conducted by a team of biomechanical engineers a few years ago,” Olson explains. “As a result of this research, the lap belt width specificsations were eliminated.”

The research showed that a two-inch lap belt interfaced better with the pelvis, actually improving performance over the then-mandatory three-inch-wide belt.

“The two-inch-wide belt does not bunch like the three-inch belt, and it fits more naturally over the pelvis,” says Warren Caswell of Sparco. “The better fit also makes it easier to tighten the two-inch belt.”

HMS Motorsport has an expansive harness-technology section on its Web site which further explains some of the benefits of the two-inch lap belt: “Since the two-inch webbing fits well within the iliac crest of the pelvis, it is less likely to slide up above the crest and cause submarining — a condition where the body slides down below the lap belt, possibly causing internal organ damage,” the site reads. “Research shows that the faster the pelvis is captured, the lower the resultant loads on the chest, head, and neck.”

Similar to the cavity in your pelvis, most all head and neck restraint devices have a specific channel or location in which the shoulder must engage in order to function effectively. With some units, accommodating a three-inch belt can be a real battle.

Initially, only a select handful of harness manufacturers offered what became known as a “HANS harness”, engineered to be used in conjunction with that pioneering head and neck restraint. But this type of harness is becoming more common every day.

“[The fact that] most of the head and neck restraints worked more effectively with a two-inch shoulder harness became an important factor in the elimination of the three-inch mandatory requirement,” Olson explains, adding, “I don’t have the exact numbers, but a considerable percentage of [manufacturers] now have submitted systems using two-inch lap belts and shoulder harnesses for certification.”

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