Our Mustang world is full of horsepower thanks to the burgeoning aftermarket that fuels our desire to go fast. Turning out 400 hp is like child's play, and the number of 500-plus-horsepower Mustangs is overwhelming. Couple that with traction-thanks to the ease of suspension bolt-ons and sticky tires-and running deep into the 11s and quicker is easy with a street car. NHRA and IHRA mandate a host of safety equipment once you hit the 11.49 and quicker realm (13.49 for convertibles). Two of those required items are a rollbar and a five-way harness.
The minimum rollbar requirement is a set of tubes that connect to the chassis/unibody in five specific locations, with six-point rollbars being the most popular style. Some people confuse a rollbar with a rollcage, but they are different types of safety equipment. A rollcage is a rollbar that has additional roof bars and a set of bars that drop down behind (or in front of) the dashboard to "cage in" the driver. A rollbar encompasses a main hoop with front- and rear-facing uprights to support the hoop in case of a rollover. A rollcage is required in cars that run 9.99 or quicker. See the sidebar for more information on NHRA requirements.
We visited DMC Racing in Halifax, Massachusetts, where the crew was installing one of the company's six-point rollbar kits in Paul Thetonia's '03 SVT Cobra. It's a great kit for the do-it-yourself crowd, as it comes prebent and prenotched for ease of installation and is 100 percent NHRA/IHRA legal. While most other kits use mild steel, this kit comes with chrome-moly tubing.
The use of mild steel versus chrome-moly is a constant debate in the chassis-building world. Chrome-moly requires a TIG welder and costs a few dollars more when compared to mild steel. A chrome-moly bar or cage can be built lighter because NHRA requires a thinner 0.083-inch wall thickness, compared to mild steel, which must have a wall thickness of 0.120 inch. Those are the minimum thicknesses for each material. Chrome-moly is a denser material, and NHRA allows it to be thinner, which translates to the lighter weight. Theoretically, the two materials are the same strength when comparing a 131/44-inch round tube in the different wall thicknesses.
DMC Racing offers a six-point...
DMC Racing offers a six-point rollbar kit that is NHRA/IHRA legal. The bars are 131/44 inches in diameter and feature a wall thickness of 0.083 inch. They come prebent and prenotched for an easy installation. Also included in the kit are 6x6 plates (0.125 inch thick) for mounting purposes. Installation can be handled over a weekend with the proper tools and a TIG welder.
The first order of business...
The first order of business is to remove the front and rear seats. The front seats are unbolted, while the rear seats are secured with the typical Ford-style clips.
If you are not adventurous, then Dennis MacPherson of DMC Racing can do the job in-house at his shop. It took us one day to do the job, however the DMC crew prepped the car before our arrival.
The Cobra we used had a set of 2x3 square-tube, through-the-floor subframe connectors (with kickouts) that DMC installed last year. Thetonia runs his Cobra on a weekly basis at New England Dragway in Epping, New Hampshire. Because of that, he chose to step up to the beefier subframe connectors. When combined with the six-point rollbar, it is "structurally superior," according to MacPherson. Thetonia will have no problem increasing horsepower and won't worry about the Cobra's unibody twisting and wasting energy, let alone creating a safer vehicle in the process.
Removing the kicker strips...
Removing the kicker strips allows us to move the carpet out of the way. The through-the-floor subframe connector and kickout that attaches to the unibody's rocker frame are noticeable in this photo. The subframe connectors were installed in anticipation of excessive dragstrip usage and eventual rollbar installation. The main rollbar hoop will be welded to the kickout square tubing. The kit includes plates that are welded to the floorpan if through-the-floor subframe connectors are unavailable.
Dan Rondeau assisted Dennis...
Dan Rondeau assisted Dennis MacPherson with the main hoop placement.
The subframe kickout's surface...
The subframe kickout's surface is cleaned before the hoop was put in place. A clean surface helps in the welding process.
Rules for Vehicles 11.49 and Quicker
NHRA has a list of mandatory items required for vehicles running 11.49-10.00 elapsed times. The most obvious ones are the five-point (minimum) rollbar and five-way harness. In addition to those items, the driver must wear a single-layer fire jacket (SFI 3.2A/1), along with a host of other upgrades. Here is a quick guide.
* Auto transmission shield (SFI 4.1 spec) for all vehicles running 10.00-10.99* Bellhousing/flywheel shield (SFI 6.1., 6.2, 6.3, or 9.1 spec) for clutch-equipped cars running quicker than 11.49* Five-point racing harness (SFI 6.1 spec)* Properly installed driveshaft loop* Clutch/flywheel meeting SFI specs (SFI 1.1, 1.2, 1.3, 1.4, or 1.5)* Harmonic balancer (SFI 18.1 spec)* Helmet (SFI 41.1A minimum or Snell-rated)* Five-point minimum rollbar* Rollbar padding
MacPherson uses a level to...
MacPherson uses a level to ensure the main hoop is installed properly. The main hoop is laid back 7 degrees.
Here is an example of the...
Here is an example of the mounting plates welded to the floorpan. Four of these plates are used in this application. This particular plate is located in the trunk.
The rear bar is installed....
The rear bar is installed. The unibody support was trimmed, so the bar fit nicely.
The list is a quick guide of additional equipment you would need if you run between 10.00 and 11.49 without exceeding 135 mph. If a racer exceeds 10.00 and 135 mph, more safety equipment is required in addition to a NHRA Competition License and NHRA-inspected rollcage. The personal safety gear is upgraded with fireproof pants and gloves along with the jacket.
Note: In no way is this list of vehicle requirements intended to supersede the NHRA rule book. It is meant to be a guide, and the NHRA rule book should be referenced when selecting safety components.
When a rollbar is installed, the driver must utilize a five-point racing harness. There are a variety of styles, and the NHRA dictates the use of SFI 16.1-certified belts. An expiration date is stamped onto the tag, and it is good for two years. Once it expires, the belts can be recertified by the manufacturer or replaced with new restraints. In years past, the NHRA allowed Y-type shoulder straps, but it has since eliminated the legality of that type of belt.
The five points of restraint come from two lap belts, two shoulder harnesses, and a crotch strap. Obviously, the lap belts and shoulder harnesses have a left and right belt. The belts measure a minimum of 3 inches wide. Lap belts and crotch straps are secured to the floor or frame using 31/44-inch bolts or according to the manufacturer's recommendations. Shoulder harnesses are attached to the rollbar by 31/44-inch bolts, or they can be wrapped around the crossbar using a special bracket to hold the belts in place. The shoulder harnesses are required to be level with the driver's shoulders or no more than 4 inches lower at the mounting point.
A pulled-back photo reveals...
A pulled-back photo reveals the passenger-side rear bar as it waits to be adjusted and welded into place.
MACPherson uses a shield made...
MACPherson uses a shield made of metal and cardboard (arrow) to protect the headliner when welding the topside of the tubes. He also utilizes a mirror to view the topside of the bar and achieve a 360-degree weld around the tubes.
Once the rear bars are in...
Once the rear bars are in place and everything is leveled properly, the main hoop is permanently welded. Until this point, the main hoop was only spot-welded.
The five belts can be joined together using a few different methods, and each one has a quick-release that unlocks all harnesses in one quick motion. The most common is a stem on the lap belt that holds three points (crotch and two shoulder harnesses); it connects to the right lap belt, which has a latch that secures the belts. One quick upward motion of the latch releases all five harnesses. The other method is a cam-lock setup. This is a unit that is usually attached on the right-side lap belt, and the other belts lock into it. One lever is used to unlock the unit, and all belts come out. It acts as a regular seatbelt clip but is designed to be more rugged and meet the SFI specs.
We've come across quite a few mistakes at the dragstrips regarding the use of a five-point safety restraint system, resulting in the driver putting himself or herself in a position to be seriously injured, even in the most minor accident. The most common blunders are loose seatbelts and missing crotch straps. Another is tightening the shoulder harness first, which causes the lap belts to ride up into the sternum. In contrast, the lap belts should be tightened first, low and tight over the hips. Then the shoulder harness can be pulled tight. Be sure to install the equipment according to the NHRA and manufacturer instructions and use it properly. In the end, it's your butt that's being saved.