Talk about taking responsibility for your own safety. When you convert a production car for racing, you remove a restraint system that has been engineered and crash-tested at great length and expense and often supplemented with an airbag system to ensure the driver and occupants are protected in the event of a crash.
You remove all that, then you install a roll cage, racing seat, window net, center net and a racing harness. You, the guy who misplaces a wrench every 10 minutes while you’re working on your car, is now assuming the role of all those engineers.
The good news is that modern race restraints are engineered by a team of engineers, too, and if you’ve ever seen someone involved in a bad racing crash and walk away, you know they work. The critical part is installing them correctly.
We contacted Impact Race Products about its new 16.5 Pro Series cam lock harnesses, which now have the adjuster integrated into the tangs that insert into the cam lock. We also spoke with vice president of sales Ben O’Connor for some tips on proper installation.
“There are a lot of resources out there, not just from us, but from other manufacturers and well,” O’Connor said. “You want to keep the belts as short as possible on the laps, and shoulders really. The reason for that is that all webbing, no matter what type it is, stretches in an event.”
For lap belts, O’Connor said the angle of the lap belt is critical. For 20-degree seatback angles, which is common in stock cars and production cars converted for racing, the restraints are going to be anchored to provide a roughly a 45-degree angle for the routing of the belts over the pelvic area. Factory anchor points are often a good place to start, and the Impact harness kit comes with anchors with metric threads that match most modern anchor points.
For mounting shoulder harnesses, the NASA CCR says they “should be mounted behind the driver and above a line drawn downward from the shoulder point at an angle of no more than twenty (20) degrees from horizontal with respect to flat ground.” O’Connor recommended keeping the mounting angle within 5 degrees above or below the level of the driver’s shoulder, again, keeping the straps as short as possible. If you’re having a custom roll cage built, this should be just another part of the process.
“If you’re going to be doing endurance racing, I can’t see using anything else other than a cam lock,” O’Connor said. “The extra money that it costs is well worth the time it’s going to save you, and I think for the most part, everybody does. I think there’s many people out there using latch and link belts. But if they are, they should really consider going to the cam locks.”
It’s important to take your time with an installation like this. Measure four times so you can drill once. Obviously, you need to do this job right the first time. These steps are for a Spec Miata, but you can follow along to get some good guidelines for installing racing harnesses in any car.
With adjusters integrated into the tangs that fit into the latch, Impact’s new 16.5 Pro Series cam lock harnesses make adjusting the belts easy because they don’t get hung up on the openings in the sides of the seat.
You’re going to mount the antisubmarine strap first, so you’ll need backing plates. We used 2-inch-wide steel plate to make a set.
Drill and chamfer the holes in the backing plates. You’re going to be doing a lot of drilling and chamfering in this job. Drill the hole to size with a conventional drill, then chamfer the opening with a stepped drill bit.
Working inside the car, start by locating the anchor points for the antisubmarine straps. According to Impact Race Products, the anchor points should be located behind the extended chest line, essentially an imaginary line drawn from the chest to the floor.
The Impact harnesses come with good illustrations for locating and mounting the belts’ anchor points. Study this carefully before drilling any holes.
According to the instructions, antisubmarine anchors should be placed 4 to 6 inches apart. We placed them 6 inches apart.
Drill and chamfer the holes for the antisubmarine anchor points top and bottom.
By using metal plates rather than washers, we could run the backing plates alongside the floor stiffener rail. This car uses the dropped floor panel from Advanced Autosports, which includes an insert for the floor stiffener.
The antisubmarine belts should be located so the camlock on the lap belt ends up being in front of your belt buckle. This test-fitting requires you to install and remove the racing seat a few times before you get it exactly right.
The lap belt anchors come with the Impact harness kit. They screw right into the factory threaded holes for the outside belt. Obviously, you want this fastener to be tight. A screwdriver through the loop provides more leverage.
Because there was no factory-threaded hole for the inside anchor, we had to drill and chamfer one on the bottom of the transmission tunnel.
Before you reinstall the seat to test-fit the belts on the driver, snug everything up so it doesn’t move when you tug on it. You can double-loop the straps as per the CCR when you’re all done.
Tighten the lap belt anchors to 45-degrees to align the straps to the correct angle, and hang the lap belts over them, with the safety catch on the bottom. Slip a small cotter pin through and bend the tabs out.
Put the seat back in for more test-fitting of how the lap belts interface with the antisubmarine straps.
With the seat in place, you can locate and wrap the shoulder straps around the harness bar. The custom cage by Blackbird Fabworx locates the straps dead even with the driver’s shoulder. Straps should be as short as possible to avoid stretch in an event, and should be no higher or lower than 20 degrees from a driver’s shoulders, according to the NASA CCR.
To ensure the belts fit right, test-fit them with your driver suit and head and neck restraint in place under the shoulder straps.
The custom cage has seat-back supports that contain the shoulder straps on the outside. C collars from McMaster-Carr keep contain them on the inside. For an additional cool factor, roll up the excess strap and zip-tie them to keep them from flapping around behind your head.
The finished product, a system of a roll cage, harnesses, seat and nets, should keep you safer than the factory restraint system you removed.