| Current Regulation | 19 Roll Bars and Roll Cages
These specifications are only sufficient for Time Attack, the specifications for roll bars and roll cages
found in the CACC General Competition Regulations are highly recommended. Roll Over protection is
highly recommended for all vehicles. Roll Over protection is mandatory for convertibles for vehicles with
completely removable tops.
19.1 General Roll Bar and Roll Cage
Basic Design Considerations:
The basic purpose of the roll bar, roll cage is to protect the driver in case the vehicle rolls over. This
purpose must not be forgotten.
The top of the roll bar must not be below the top of the driver’s helmet when the driver is in the normal
driving position and must not be more than 15.24 cm (6 inches) behind the driver. It is strongly suggested
that the roll bar be at least 7.62 cm (3 inches) above the drivers’ helmet. In the case of two drivers, both
drivers must be the roll bar height requirement, however, only one driver must be within six inches of the
roll bar. In a closed car with a roll bar/cage, it must be as close as possible to the interior top of the car.
The roll bar must be designed to withstand compression forces resulting from the weight of the car
coming down on the roll structure, and to take fore-and-aft loads resulting from the car skidding along the
ground on the roll structure.
Two verticals forming the sides of the hoop must not be less than 38.10 cm (15 inches) apart, inside
dimension. It is desirable that the roll bar extend the full width of the cockpit to provide maximum bearing
area in all soil conditions during rollovers.
The roll bar vertical members in a formula car must be not less than 38.10 cm (15 inches) apart, inside
dimension, at their attachment points to the uppermost main chassis member.
An inspection hole of at least 4.7 mm (3/16 inch) diameter must be drilled in a non-critical area of a roll
bar member to facilitate verification of wall thickness. This must be at least 7.63 cm (3 inches) from any
weld or bend. If a CACC vehicle logbook is to be issued, tube thickness may be verified by ultrasonic
testing by a CACC official.
It is recommended that steel gusset plates be used at all welds. Gussets must be at least 5.0 cm (2
inches) long on each leg and 4.7 mm (3/16 inches) thick.
It is recommended that roll bar be coated only with a light coat of paint. If however, a roll bar is chromeplated, it is recommended that the structure be normalized.
Post or tripod types of roll bar are not acceptable.
19.2 Material
After 9/22/85, aluminum is not an acceptable alternate material. Cars using aluminum roll bars/cages
must file proof that the structure was approved prior to 9/22/85
The roll bar hoop and all braces must be of seamless DOM mild steel tubing. Chrome alloy tubing such
as 4130 is not recommended since the strength of the area adjacent to welds will be impaired if the
structure is not normalized, and because of the difficulty in making satisfactory welds.
The size of tubing to be used will be determined on the basis of weight of the car. The following minimum
sizes are required:
Roll Bar:
Over 1134 kg (2500 lbs.) 1.50 o.d. x 0.120" wall or 1.75” x 0.095” wall
Over 680 kg (1500 lbs.) 1.50" o.d. x 0.950" wall
Under 680 kg (1500 lbs.) 1.375" o.d. x 0.95" wall
Roll Cage:
Over 1225 kg (2700 lbs.) 1.50 o.d. x 0.120" wall or 1.75” x 0.095” wall
Over 770 kg (1700 lbs.) 1.50" o.d. x 0.950" wall or 1.625” x 0.080”
Under 770 kg (1700 lbs.) 1.375" o.d. x 0.080" wall
Fabrication:
One contiguous length of tubing must be used for the hoop member with smooth continuous bends and
no evidence of crimping or wall failure.
All Welding must be of the highest possible quality with full penetration and will be subject to very critical
inspection. TIG or MIG are the preferred welding processes.
19.3 Bracing
It is recommended that bracing be of the same size tubing that is used for the roll bar hoop itself.
All roll bars must in a fore-and-aft direction with the brace attached within the top one-third of the roll
hoop, and at an angle of at least thirty degrees from the vertical. It is strongly recommended that two (2)
such braces be used, parallel to the sides of the car, and placed at the outer extremities of the roll hoop.
Such braces should extend to the rear wherever possible.
It is suggested that roll bars include a transverse brace from the bottom of the hoop on one side, to the
top of the hoop on the other side.
19.4 Mounting Plates
Roll bars and braces must be connected to plates welded or bolted to the frame or floor of the vehicle.
Mounting plates and gussets must be:
19.4.1 At least 129 cm square (20” cm sq.) in area and 0.2cm (0.08”) minimum thickness on unit body
vehicles for weld on plates OR 0.47cm (0.1875”) minimum thickness for bolt on types.
19.4.2 At least 51.6 square cm (8 square inches) and 0.47cm (0.1875”) minimum thickness on frame
type construction for both welded or bolt on types.
Where bolts are used, the bolts must be at least 10 mm and class 8.8 (3/8 inch, grade 5). Square head
bolts and nuts are prohibited.
In the case of cars with unitized or frameless construction, mounting plates may be used to secure the roll
bar structure to the floor of the car. The important consideration is that the load be distributed over as
large an area as possible. A backup plate of equal size and thickness must be used on the opposite side
of the panel with the plates through-bolted together.
19.5 Removable Roll Bars
Removable roll bars and braces must be very carefully designed and constructed to be at least as strong
as a permanent installation. If one tube fits inside another tube to facilitate removal, the removable portion
must bottom on the permanent mounting, and at least two (2) bolts must be used to secure such a joint.
The telescope section must be at least 20.8 cm (8 inches) in length.
19.6 Installation on Cars of Frameless Design
It is important that roll bar structures be attached to cars in such a way as to spread the loads over a wide
area. It is not sufficient to simply attach the roll bar to a single tube or junction of tubes. The roll bar must
be designed in such a way as to be an extension of the frame itself, not simply an attachment to the
frame. Considerable care must be used to add as necessary to the frame structure itself in such a way as
to properly distribute the loads. It is not true that a roll bar can only be as strong as any single tube in the
frame.
On cars of frameless construction, consideration should be given to using a vertical roll bar hoop of 360
degrees completely around the inside of the car and attached with suitable mounting plates. This type of
roll bar them becomes a substitute for the frame.
19.7 Sedans and Coupes
It is recommended but not mandatory that all closed cars utilize a roll cage type construction. One hoop
must be placed behind and above the driver’s head from one side of the car to the other, with another
similar hoop in front supporting the front pillars. Horizontal connecting bars must connect the two hoops at
each side of the top. A transverse brace must be used on the rear hoop from the bottom of one side to
the top of the other side. A diagonal brace must be used on each side of the car extending from the top of
the rear hoop to the floor at the rear of the car.
19.8 Other Roll Bar Designs
The Technical and Safety Inspector may accept roll bars of alternate materials or design upon
presentation of data verifying strength equivalence.
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| Proposed Regulation | The specifications for roll bars and roll cages are found in the CACC General Competition Regulations. Roll Over protection is highly recommended for all vehicles. Roll Over protection is mandatory for convertibles for vehicles with
completely removable tops.
NOTE: Foot intrusion bars, while recommended, are not required for Time Attack Passing/Hill Climb.
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| Reason for Rule Change | Time Attack is viewed as the stepping stone to race. If a driver builds his cage to CACC Time Attack Regulations and then finds that it does not meet the CACC General Competition Regulations because the CACC TA regulations are not as stringent, that would be a significant complication. This would create much confusion not to mention be an expensive correction.
Further, having this information in Time Attack is simply not required. CACC Race Regulations rely completely upon the CACC GCR for roll cage information; therefore, it is time for Time Attack to adopt the same approach.
The one exception would be that Time Attack does not require foot intrusion bars, although they are recommended.
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