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triangulate the main hoop and it is highly recommended that this brace be attached at the top on the driver’s side and attached to the bottom on the “passenger” side.
An additional horizontal bar to support the main hoop is recommended. In addition, this bar should be installed at the height no more than 2” above or below the driver’s shoulders while seated in the driver’s position. The shoulder harness should be attached to this bar. A head restraint is recommended.
Mounting Plates: The main hoop and braces must be attached to the frame of the car whenever possible. Mounting plates must be used for this purpose. In the case of cars with unitized or frameless construction, mounting plates must be used to secure the structure to the floor and body of the car. The important consideration is that the load be distributed over as large an area as possible, with 4”x 4x1/8” the minimum size desired for spreader plates. The plates must be tack welded or continuous welded to the car's frame. On some vehicles this exact size is not an option and square area of the spreader plate must be calculated to spread the maximum load expected in the worst-case scenario.
Other Designs: Deviations from the above will be considered. NHRA approved 9.99 cages will be accepted but any factory side-impact door bar must remain. The NASCAR design is preferred.
Roll Bar Padding: Roll bar padding must be used to protect the occupants in all areas of possible contact. It must be of material (readily available) that is designed for this purpose. SFI-approved padding is highly recommended.
Roll Cage Tubing Chart:
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Weight
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Steel
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Minimum Tubing Size
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Under 2700 lbs.
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Mild Steel
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1.50" O.D. X .120 wall
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Alloy Steel
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1.50" O.D. X .090 wall
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Over 2700 lbs.
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Mild Steel
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1.75” O.D. X .120 wall
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Alloy Steel
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1.75" O.D. X .090 wall
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It is highly recommended that vehicles weighing in excess of 3200 pounds use 2.00" tubing.
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