Lateral-g Forums - Cage or Roll Bar Specs?

Bill, this is the most technical info I could find. You will want to get a hold of a rulebook to be sure this is the most up to date. I know on Jan 1, 2005, the 11.99 break moved to 11.49.

ROLL BARS{reprint from IHRA Rulebook}
Mandatory in all cars running 11.49 or quicker, or per class
requirements. All roll bars must be within 6 inches of the rear or
side of the driver's head, extend in height at least 3 inches above
the driver's helmet with driver in normal driving position, and be at
least as wide as the driver's shoulders or within 1 inch of the
driver's door. Rollbar must be adequately supported or cross-braced
to prevent forward or lateral collapse. Rear braces must be
of the same diameter and wall thickness as the roll bar and
intersect with the roll bar at a point not more than 5 inches from
the top of the roll bar. Sidebar must be included on driver's side
and must pass the driver at a point midway between the shoulder
and elbow. Swing-out sidebar permitted. All roll bars must have in
their construction a cross bar for seat bracing and as the shoulder-
harness attachment point; cross bar must be installed no more
than 4 inches below, and not above, the driver's shoulders or to
side bar. All vehicles with OEM frame (i.e. pickup truck where body
bolts to framerails) must have roll bar welded or bolted to frame.
Installation of frame connectors on unibody cars does not
constitute a frame; therefore, it is not necessary to have the roll bar
attached to the frame. Unibody cars with stock floor and firewall
(wheeltubs permitted) may attach roll bar with 6-inch x 6-inch x
.125-inch steel plates on top and bottom of floor bolted together
with at least four 3/8-inch bolts and nuts, or weld main hoop to
rocker sill area with .125-inch reinforcing plates, with plates welded
completely. All 4130 chrome moly tube welding must be done by
approved TIG heliarc process; mild steel welding must be done by
approved MIG wire feed or approved TIG heliarc process. Welding
must be free of slag and porosity. Any grinding of welds prohibited.
Roll bar must be padded anywhere driver's helmet
may contact it while in driving position. Adequate padding must
have minimum 1/4-inch compression or meet SFI Spec 45.1.

ROLL CAGE{reprint}
Mandatory in all cars running quicker than 10.99 seconds or faster
than 135 mph, or per class requirements. Cars with unaltered
firewall, floor and body (from firewall rearward, wheeltubs
permitted) running between 10.00 and 10.99, roll bar permitted in
place of roll cage, or per Class Requirements. Cars with altered
firewall, floor faster than 11.49 must have rollcage and window net.
All cage structures must be designed in an attempt to protect the
driver from any angle, 360 degrees. All 4130 chrome-moly tube
welding must be done by approved TIG heliarc process; mild steel
tube welding must be approved MIG wire feed or TIG heliarc
process. Welding must be free of slag and porosity. Any grinding of
welds prohibited. Additionally, roll cage must be padded anywhere
the driver's helmet may contact it while in the driving position.
With driver in driving position, helmet must be in front of main
hoop. If helmet is behind or under main hoop, additional tubing,
same size and thickness as roll cage, must be added to protect
driver. Main hoop may be laid back or forward, but driver must be
encapsulated within the required roll cage components. On
unibody cars with stock floor and firewall (wheel tubs permitted),
the roll cage may be bolted or welded to the floor/rocker box via 6-
inch x 6-inch x .125-inch steel plates
Unless attaching to OEM floor or frame, the minimum requirements for a
frame member to which a roll cage member is attached are 1 5/8-
inch x .118-inch MS or .083-inch CM round and/or 2-inch x 2-inch
x .058 MS or CM rectangular.
All cage structures must have in their construction a cross bar for
seat bracing and as the shoulder-harness attachment point; cross
bar must be installed no more than 4 inches below, and not above,
the driver's shoulders, or to side bar. All required rear braces must
be installed at a minimum angle of 30 degrees from vertical and
must be welded in. Side bar must pass the driver at a point midway
between the shoulder and elbow.
Unless an OEM framerail is located below and outside of driver's
legs, a rocker or sill bar, minimum 1 5/8-inch x .083 CM or .118 MS
or 2-inch x 2-inch x .058-inch CM or MS rectangular, is mandatory
in any car with a modified floor or rocker box within the roll-cage
uprights (excluding 6 square feet of transmission maintenance
opening). Rocker bar must be installed below and outside of
driver's legs and must tie into the main hoop, the forward hoop,
frame, frame extension, or side diagonal. Rocker bar may not tie
into swing-out side bar support. If rocker bar ties into side diagonal
more than 5 inches (edge to edge) from forward roll-cage support
or main hoop, a 1 5/8-inch x .083 CM or .118 MS brace/gusset is
mandatory between the diagonal and forward roll-cage support or
main hoop.