Roll Cages Demystified

Whether you're looking for a quality chassis shop to take care of the installation or taking the project on yourself, researching the right roll cage and installation process is time well spent. Things to think about when making your decision include how you'll use the vehicle, today, tomorrow and many years from now. Be aware of the safety pros and cons if you plan on using the car for racing and street driving with passengers on board.

Driver safety, performance, NHRA / SFI regulations, class and use of the car all have to be factored into the decision. Here are some important points and tips we share with our clients prior to designing, building and installing roll cages for them.

• Strength and installation of a roll cage directly impacts driver safety.
• In drag racing applications roll cages need to be installed correctly, per NHRA (National Hot Rod Association) and SFI specifications.
• Roll cages add a great deal of strength by tying into the frame and making the chassis more ridged.
• Strengthening and reinforcing the chassis can also improve 60ft times.

Picking Roll Cage Points

This is a very important step in choosing your roll cage. Points are parts of the cage where a bar comes in contact with the frame. The speed of the car and the requirements of NHRA certifications for that speed, typically determine the minimum number of points required for a roll cage.  Whether you install the roll cage yourself or hire a professional, be sure the installation is done to the following standard:

• OEM cars can have roll cages directly attached to the chassis.
• Stock floor pan cars require a 6 x 6 x 1/8 steel plate be welded to the floor, prior to attaching any of the cage bars to the car.
• Bolted-in bars require a pair of 6-inch steel plates (one underneath, one above), with four 3/8-inch bolts through the rocker sill, anchoring the two plates together.​

NHRA requires a ROLL BAR be installed in:

• Vehicles running 11.00 to 11.49 in the 1/4-mile
• Vehicles running 7.00 to 7.35 in the 1/8-mile (including those with T-tops)
• Convertibles running 11.00 to 13.49 (7.00 to 8.25)
• Dune-buggy-type vehicles running 12.00 or lower

NHRA requires a ROLL CAGE be installed in:

• Vehicles running 10.99 (6.99) or quicker or exceeding 135 mph.
• A roll bar is permitted in place of a roll cage on any full-bodied vehicle with an unaltered firewall, floor, and body running between 10.00 and 10.99 (6.40 and 6.99)
• An 8 point roll cage is the advised minimum standard

Roll Cage Materials

When choosing Roll cage materials consider performance, weight, welding / installation and budget:

Chromoly 4130

• Widely used because of its strength and light weight properties
• Roll bar cage bars can be fabricated with a thinner inner wall thickness (0.83)
• Outer diameter of all bars needs to be 1 5/8"
• After a NHRA/SFI certification of 25.5 chromoly is the only material allowed

4130 chromoly can only be welded using an approved TIG heliarc process, which can be a much more tedious and time consuming, increasing the associated costs.

Mild Steel

• Mild steel tubing (0.134 wall thickness) brings more weight, but is more affordable per foot.
• Outer diameter of all bars needs to be 1 5/8"
• Installation costs will be lower as mild steel is allowed to be MIG welded with is a faster less involved process.

Helpful Tips for Roll Cage Installation:

• Always make sure your battery is disconnected before welding on a vehicle as the current can feed threw through and damage electronics.
• Protect interior parts and paint from weld spatter, tools etc. Be sure that anything that could catch fire during welding is removed or property protected. A couple of nice leather welding blankets are great for this.
• Be very careful around windows as weld spatter can hurt and damage the glass.  Always prep any area to be welded very thoroughly as the weld and it's strength is nothing without a good clean surface. We like to use 3M sanding discs. 
• Grinding and plating of the welds is prohibited by NHRA/SFI. If you are not a confident welder, leave it to the pros.
• Serious racers at the level of certification of a 25.5 chassis use SFI approved padding in the funny car cage area where the drivers helmet can come in contact with the roll bar (required by NHRA/SFI).
• If you're a "do it yourselfer" considering building or installing a roll bar/cage yourself, consider becoming a NHRA member and purchase a copy of the NHRA Rulebook (details available at http://www.nhra.com)