Strap In: How to Properly Install a Racing Harness

On the surface, a driver harness seems so simple: Some webbing is strapped across the driver’s hips and chest and secured to the car. Once you start considering the forces at work, though, it gets complicated. HMS Motorsport, the U.S. distributor for Schroth harnesses, publishes a harness safety checklist and allowed us to share it with our readers. If every item on these lists is true of your harness, congratulations. Otherwise, you may not be as safe as you thought.

Shoulder Belts

Shoulder belts are correctly wrapped to the harness bar or cage.

Only one bar of the three-bar adjuster is showing, and it is adjacent to the harness bar.

Three-bar adjuster is wrapped and positioned directly against the harness bar/cage or mounting hardware.

Shoulder belt three-bar adjusters are not obstructing the belt flow through the shoulder belt opening and are positioned behind the seat back–as close as possible to the bar.

The belt is not twisted or constricted through the shoulder belt opening in the seat. Shoulder openings allow direct passage from the top of the HANS or shoulders–directly to the attachment points.

Shoulder belts are securely fixed in position so that they cannot slide horizontally on the harness bar or roll cage.

Shoulder belts run down from HANS or shoulder to the harness bar at an angle from zero degrees to a max of negative 30 degrees. In no case should the shoulder belt run at an upward angle from the shoulder or HANS to the attachment points.

Shoulder belts are secured with the proper spacing between the anchor points and cross over each other as needed.

Lap Belts

The angle of the lap belt is between 60 degrees (touring cars) and 80 degrees (formula cars) measured from the horizontal, allowing the lap belt to ride properly over the pelvis. An angle less than 50 degrees may allow submarining and cause the lap belt to ride up into the abdomen, causing injury to the soft-tissue region.

When wearing the lap belt, the webbing is not bunched or folded around the seat opening. It must lay flat. The adjusters are not caught or positioned in the opening, which may cause accidental release or failure when loaded.

Check beneath the webbing path to ensure it is not rubbing on any edges of bolts, seat brackets or seat openings that may cut or abrade the webbing.

The lap belt is positioned close to the seat at an angle–not more than 25 to 30 degrees off the seat.

The snap hooks are correctly clipped to the eye bolts, with the latch toward the bottom and secured with wire or a cotter pin.

The snap-on bracket does not bind on the eye bolt when pulled in the direction the belt is worn. Adjust alignment of eye bolt using additional wavy washers.

The wrap-in end of a bolt-in or snap-on bracket has the three-bar adjuster as close to the bracket as possible, and the final loop of the wrap is complete.

The bolt-in lap belt bracket pivots at the bolt, allowing the webbing to align with the flow of the webbing across the lap with an even load across the bracket. Use a pivot sleeve or a lock nut and red Locktite to back it off just enough to pivot.

The webbing load of any bolt-in or snap-on bracket must be in plane with the flat side of the bracket. Pulling at a 90-degree angle will reduce the maximum load of a bracket 60 percent.

Anti-Sub Straps

The sub-strap opening in the seat bottom is positioned properly.

Sub-strap must not be routed around the front of the seat.

A five-point (single) sub-strap is center-mounted 10 to 20 degrees forward of the tangential plane of the shoulder belts through the sub-strap hole.

A six-point (dual) sub-strap is mounted a minimum of 20 degrees rearward from perpendicular (drawn to the floor through the sub-strap hole in the seat, immediately in front of the groin.) Two points of attachment should be approximately 4 to 6 inches apart–2 to 3 inches to the right and left of centerline.

Note for formula cars where the driver is sitting on the sub-straps: Attach sub-straps rearward in approximately the same location as the lap belts. This type of setup is typically used with a formula-style or hybrid-style looped sub-strap.

Adjusters on the sub-straps are not positioned or caught in the sub-strap opening in the seat.

Snap-on or bolt-in brackets are attached properly with approved backing plates using the hardware provided by the harness belt manufacturer.

Never mix hardware from different manufacturers.

If using double brackets for bolt-in sub-strap applications, wrap is as pictured with 2 inches of extra webbing.

The sub-strap webbing is pulling in the proper plane on the hardware.

Shoulder Spacing

The following formula is used to determine the spacing of the shoulder belts at their attachment to the harness bar or cage.

Y = Z - (X * 0.50)

X = Distance from shoulder points to attachment. Measure from the highest shoulder point (on top of the HANS, if worn). Z = Distance between the middle points of both shoulder harnesses. Y = Approximate distance between anchor points (measured middle to middle of webbing at anchor point).

The shoulder belts will cross over when anchor points are located more than 18 inches behind the seat backrest.

We recommend a distance of 8 inches or less from the back of the HANS to the harness bar when possible.

Belt Wrapping

1. Webbing should wrap from the body-facing side of the bracket up into Slot 1.

2. Pull through approximately 11 inches of belt and then fold down through Slot 3, temporarily leaving 2 inches of slack.

3. Fold back up from the body side through Slot 1 and back down through Slot 2.

4. Fold back through Slot 3 and finally through Slot 1, with the webbing exiting to the underside of the belt.

5. Pull the lap belt firmly to ensure the wrap is tight. Leave a tail of approximately 4 inches. Excess webbing can be cut off, providing that the remaining edge is heat-sealed to prevent fraying.

Other Information

High-density padding is used around the cage where the driver’s head could potentially come in contact with it. Padding should be either SFI 45.1 or FIA Type A. Flat surfaces should use SFI 45.2 sheet padding.

Zip-ties are used around all roll-bar padding to keep it in place.

Headrest padding–if used–should meet SFI 45.2 standards. (Soft padding will allow the head to bounce off the headrest, increasing head and neck tensions.)

All webbing and hardware is in good condition. No signs of damage, cuts, fading, elongation, etc. Must be within date spec for competition use: SFI says two years from manufacturing; FIA says within five years. Schroth Rallye-series belts do not have an expiration date, but HMS recommends changing them every seven to 10 years or sooner, depending on the condition of the webbing.

Source

HMS Motorsport
hmsmotorsport.com
(978) 774-1615

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