Seat belt mounting location

With the untimely passing of Dale Earnhardt and the warning about the MOMO belt defects it seemed like a good time to talk about proper installation of a restraint.

The heart of any restraint system is the lap belt. The path of least resistance is to attach the new belt to the original factory lap belt mounting points. After all, they're intended for the purpose, they're strong enough. They must be ideal! Generally THEY ARE NOT!

Most every factory lap belt mounting point is positioned to far back to be of much good for a high performance lap belt application. When you buy a belt or a complete harness system it will come with an instruction sheet (that most people never look at) and a disclaimer which states something to the effect "There is no warranty of this product because we have no control of its installation".

Correct installation is paramount in the proper function of a restraint system. The rule of thumb for locating lap belt mounting points is as follows:Locate the point where a line parallel to the seat back intersects a line parallel to the seat bottom. Project that point straight down to the floor. Your lap belt mounting points will be located 2 1/2 inches forward of a transverse line identified by this procedure.

You will find that this point is as much or more than 10 inches forward of the factory mounting points. By mounting the lap belt in this way you create a belt that holds your pelvis down and not a belt that holds your abdomen back. The better anchored in the car you are, the better you drive and are usually quicker.

Another must in installation is that the belt must run without interference from its mounting point to its latching point. Those of you with a racing seat probably have slots for the belts to pass through. The webbing must pass through the slots without being redirected by the edges of the slot. This cannot be achieved when the original mounting points are used.

One of the problems in locating the lap belt points in this way in a Spitfire or GT-6 is the fact that the inner points are right in the drive shaft hump. Another is providing adequate reinforcement for new mounting points. Whether you provide backup plates for through the floor mounts or create a roll cage design that provides mounting points, it is time well spent.

There are other considerations for fitting the rest of the components of a restraint system but the lap belt is the first step in getting you as safe as you can be in the drivers seat.

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