How to properly install a racing harness

By Per Schroeder
Jun 10, 2022 | Harness, Safety, seat belt | Posted in Safety | From the May 2007 issue | Never miss an article

Photography by Per Schroeder

It’s not the fall that hurts you, it’s the sudden stop. What’s true for falling down an elevator shaft or off a bridge goes for motorsports, too. 

You’re relatively safe inside your car as it flies uncontrollably off the track. That is, you are until it strikes the retaining wall or some other immovable object and leaves your fate in the hands of basic physics.

If your harness properly holds your body in place and allows it to come to a safe, controlled stop, then odds are strong that you’ll emerge from the wreck okay. On the other hand, should a belt fail or become disconnected during a crash, well, then things aren’t looking so good for you.

A racing harness may look simple, since at first glance it’s not much more than some nylon webbing and a few metal buckles. However, some thought needs to go into the details, such as the angle of the belts, how they slide through the seat’s harness holes, and even how they clip into their mounting points. According to HMS Motorsport’s Joe Marko, a driver can live or die by these simple, almost mundane details. 

Marko is a safety guru whose credentials include work as the national safety steward for BMW CCA Club Racing and service on the National Safety Advisory board for the SCCA. He is also the man behind the distribution of Schroth Racing harnesses here in the States. The combination of well-engineered belts and excellent customer service has allowed HMS and Schroth to become the go-to choice for many racing teams, up to and including the top tiers of NASCAR competition—in addition to countless autocrossers and track day participants. 

Joe came by our shop and showed us how to properly mount a harness in a sedan. This process may seem straightforward, but it’s the details that matter. In addition to these guidelines, don’t forget to follow the manufacturer’s instructions that came with your own belts.

Starting where the lap belts join the car itself, these clip-in-type mounts should always be clipped in from the top. A small piece of safety wire or a clip then needs to pass through the small hole in the safety latch to keep the belt from disconnecting from its eyebolt. 

The lap belt should mount to the floor, tunnel or factory seat belt mount so that the belt passes through the slots in the seat and over the driver’s hip bones. The goal is to create as little twisting as possible. In this case, it would have been better to mount the harness to the belt mount on the seat, not the floor itself. 

The harness should be adjusted so that the adjustment bars (either pull-up or pull-down type) are at least 11/2 inches away from the slots in the seats. If the sliders are closer than that, they will interfere during a collision. 

Joe recommends that a piece of FIA-approved roll cage padding be used as a locator for the shoulder straps. By installing a piece of padding where each of Joe’s hands are resting on the cage, you can keep the shoulder belts from separating during a hard, multi-hit collision. 

It’s pretty easy to roll up the extra shoulder webbing to keep it from flapping around. The shoulder harnesses should be mounted to a roll cage harness bar no more than eight inches behind the seat. This arrangement should allow the belts to be mounted 20 degrees below the driver’s shoulders.

The antisubmarine belt or belts should pass downward through the hole in the seat and to the floor pan. These straps should be mounted so both they and the shoulder belts together form a straight line to the floor. The single sub-straps used on five-point harnesses can be mounted at a 20-degree angle forward of that point, while the double straps found on six-point harnesses can be mounted up to 20 degrees behind that point. Double anti-sub straps are recommended to reduce injuries to the tender bits.

If your car has multiple drivers, make sure that the seat belt adjustment and mounting points work for each and every driver. One lap belt mounting point or adjustment range might not work for every body type. It’s up to everyone involved to make sure that all of the drivers are safe. 

Some seat belts have large sewn areas that can complicate proper tension adjustment. These Impact Racing belts needed to be readjusted so that the harness could be correctly snugged down and not interfere with the holes in the racing seat. 

A racing harness is designed to survive only one major impact. These Schroth belts were in our MINI Cooper S race car when our co-driver bounced it off a tire wall. The puckering shows where the material was stretched and burned inside the three-bar adjuster during the impact. This belt is no longer suitable for use.

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