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2011 OPEN WHEEL MODIFIED RULES
All interpretations of these rules by Bronson Speedway officials are FINAL.
CAR/FRAME:
Cars must weigh 7 lbs. per cubic inch. Minimum weight 2,500 lbs. Maximum 56% left side weight.
Aluminum head cars must run Maximum 54% left side weight.
1. Factory production complete full 1965 or newer parallel American passenger car frames only.
Fabricated front clip permitted - deduct 1% left side weight.
2. Frames may be cut in the rear only at a point no further than 36 inches from center of rear end housing.
3. Frames will not be widened or narrowed and must be able to support the roll cage on both sides. Front
cross members may be notched for radiator clearance only.
4. Minimum frame to ground clearance = 4 inches.
5. Front suspension and steering may not be altered. Heim joint permitted in place of tie rod end. Stock
passenger car spindles only. No fabricated spindles. Lower A-frames cannot be altered or relocated.
6. Tubular upper A-frames allowed. Mounting point may be relocated.
7. No coil over shocks allowed either front or rear. No homemade coil covers used anywhere on vehicle.
8. No Jeep, Bronco, Sports car, 4-wheel drive, front-wheel drive frames allowed.
9. Rear of frame may be altered to accept leaf or coil springs. Any coil springs permitted. Must be at least
4 ½ inches outside diameter. No fiberglass springs allowed. No torsion bars allowed in rear.
10. No hydraulic, ratchet or electric weight jacks anywhere in or on the car.
11. One shock per wheel only.
12. Minimum wheel base 108 inches. Wheel base must be same on both sides. 1/2" plus/minus tolerance
from side to side.
13. No aluminum suspension components.
14. No chassis or suspension adjustments from driver's seat.
BODY:
1. 1965 or newer American passenger cars only (no panel vans or station wagons). May use
steel, aluminum, or fiberglass full size roof. Must be stock in appearance. Stock appearing front
windshield and rear window support.
2. Fire wall and floor boards are mandatory. All body parts should be recognizable as factory production
vehicle. Fiberglass or metal duplicates of body parts are permitted. Hand made body parts may be
constructed of steel, fiberglass, or aluminum, but should be recognizable as factory production. All cars
must be neat in appearance.
3. All cars will be numbered with large numbers at least 18” high, in door area on both sides and on the
roof facing scoring tower.
4. Original roof line of car must be maintained with maximum drop of 4 inches-rear to front. No wings
allowed. One spoiler not to exceed 5” x 60” allowed on rear of car to be placed within the last 5 inches of
the deck lid.
5. No ground effects allowed.
6. Engine compartment will remain open, no side panels.
7. Hood may have a maximum of 4” drop and must be enclosed at the rear of the hood.
8. Bodies may not extend any further forward than the back of the engine block.
9. Rear of bodies to be securely and completely closed in with a panel at least 8” high.
10. Driver and passenger side window opening = minimum 14 inches.
RADIOS/MIRRORS
1. No radios permitted. Anyone caught with driver/crew communication will be disqualified.
2. Mirrors permitted.
ENGINE
1. Any American made engine may be used as long as rear of engine (bell housing flange) is mounted at
least 72” forward from center line of the rear axle. Engine offset = no more than 2” from center of
cross member. Engine height minimum will be 11” from ground to front center of crankshaft.
2. Any engine used in competition must have been available in conventional passenger cars. No machine
work allowed on outside of engine block. Crate engines permitted.
3. No aluminum engine blocks.
4. All cars must use a wet sump oiling system. All oil pumps must mount in stock location on block.
5. No vacuum pumps.
ASPIRATION:
1. Any two (2) or four (4) barrel carburetors .
2. Must be naturally aspirated.
3. No fuel injection.
4. No electric fuel pumps.
5. No magnetos.
TRANSMISSION:
1. Only OEM production type transmissions allowed 3 speed, 4 speed, or automatic.
2. No "in and out" boxes.
3. Transmission must be clutch operated.
4. From standing position, driver must be able to engage car in gear and move
forward and then backwards-at any time.
5. Clutch type transmission must be equipped with an explosion proof steel bell housing.
6. After market multi-disk allowed. 5" minimum diameter.
7. All cars must be self-starting.
DRIVE SHAFT
1. Drive shaft loop is required and must be constructed of at least ¼ “ by 2” inch steel and should be
mounted no more than 6” from the front of the drive shaft.
2. The Drive shaft must be painted white.
3. No aluminum drive shafts.
REAR END:
1. Any passenger car type rear end may be used.
2. Quick change rear end allowed. Center section and side bells may be aluminum. Axles and tubes
must be steel.
EXHAUST:
1. Exhaust system must be mounted in such a way as to direct spent gases away from the cockpit of the
vehicle and away from any fuel sources.
STEERING / BRAKES:
1. O.E.M steering box only. No rack and pinion allowed.
2. No center steering.
3. No aluminum steering components.
4. (4) wheel working brakes required.
FUEL CELL:
1. Maximum of 22 gallon fuel cell mandatory. Fuel cell must be in 22 gauge steel container. Minimum
fuel cell to ground clearance = 8 inches.
ROLL CAGE:
1. Must consist of continuous hoops not less the 1.666” outside diameter and must have a wall
thickness of at least .095.
2. Must be frame mounted at no less than six (6) points.
3. Must consist of a configuration of front and rear hoops connected by tubing on the sides or side
hoops. Drivers head must not protrude above the cage with helmet and strapped in the drivers seat.
4. Low carbon, mild steel tubing is recommended. No brazing or soldering allowed.
5. Protection of feet is mandatory. Bar across back of engine with vertical bars and rub rails, or similar
protection.
6. No brace bars forward of cage may be higher than stock hood height.
7. Driver door bars must be as parallel with the ground as possible and located perpendicular to the
driver as to provide maximum protection for the driver, but without causing undue difficulty in
getting into or out of the vehicle. The side door bars must be welded to the front and rear of the roll cage
member.
BUMPER:
1. Bumpers must be used front and rear. No sharp edges permitted.
2. Front bumper must be mounted frame end to frame end with the bottom loop parallel to the ground.
Must be made of a minimum of 1 ¼ “ tubing and must be able to support the car if lifted by the
wrecker.
3. Rear bumper, nerf bars, and bodies must not extend beyond the width of the tires.
4. Rear bumper must protect the fuel cell.
5. Front and rear bumpers must have minimum 18” ground clearance. Measured in center.
WHEELS / TIRES:
1. Maximum overall track width (front or rear) shall not exceed 78 inches from outside of the tire right
side to outside of the tire left side. Maximum ½ “ spacer between hub and wheel. No wheel adapters
allowed. No tire warmers or air bleeders.
2. Steel racing wheel only. Maximum 8" wheel width.
2. Tires are to be Track Approved.
The track reserves the right to add weight at its discretion in the fairness of competition.
All interpretations of these rules by Bronson Speedway officials are FINAL.
CAR/FRAME:
Cars must weigh 7 lbs. per cubic inch. Minimum weight 2,500 lbs. Maximum 56% left side weight.
Aluminum head cars must run Maximum 54% left side weight.
1. Factory production complete full 1965 or newer parallel American passenger car frames only.
Fabricated front clip permitted - deduct 1% left side weight.
2. Frames may be cut in the rear only at a point no further than 36 inches from center of rear end housing.
3. Frames will not be widened or narrowed and must be able to support the roll cage on both sides. Front
cross members may be notched for radiator clearance only.
4. Minimum frame to ground clearance = 4 inches.
5. Front suspension and steering may not be altered. Heim joint permitted in place of tie rod end. Stock
passenger car spindles only. No fabricated spindles. Lower A-frames cannot be altered or relocated.
6. Tubular upper A-frames allowed. Mounting point may be relocated.
7. No coil over shocks allowed either front or rear. No homemade coil covers used anywhere on vehicle.
8. No Jeep, Bronco, Sports car, 4-wheel drive, front-wheel drive frames allowed.
9. Rear of frame may be altered to accept leaf or coil springs. Any coil springs permitted. Must be at least
4 ½ inches outside diameter. No fiberglass springs allowed. No torsion bars allowed in rear.
10. No hydraulic, ratchet or electric weight jacks anywhere in or on the car.
11. One shock per wheel only.
12. Minimum wheel base 108 inches. Wheel base must be same on both sides. 1/2" plus/minus tolerance
from side to side.
13. No aluminum suspension components.
14. No chassis or suspension adjustments from driver's seat.
BODY:
1. 1965 or newer American passenger cars only (no panel vans or station wagons). May use
steel, aluminum, or fiberglass full size roof. Must be stock in appearance. Stock appearing front
windshield and rear window support.
2. Fire wall and floor boards are mandatory. All body parts should be recognizable as factory production
vehicle. Fiberglass or metal duplicates of body parts are permitted. Hand made body parts may be
constructed of steel, fiberglass, or aluminum, but should be recognizable as factory production. All cars
must be neat in appearance.
3. All cars will be numbered with large numbers at least 18” high, in door area on both sides and on the
roof facing scoring tower.
4. Original roof line of car must be maintained with maximum drop of 4 inches-rear to front. No wings
allowed. One spoiler not to exceed 5” x 60” allowed on rear of car to be placed within the last 5 inches of
the deck lid.
5. No ground effects allowed.
6. Engine compartment will remain open, no side panels.
7. Hood may have a maximum of 4” drop and must be enclosed at the rear of the hood.
8. Bodies may not extend any further forward than the back of the engine block.
9. Rear of bodies to be securely and completely closed in with a panel at least 8” high.
10. Driver and passenger side window opening = minimum 14 inches.
RADIOS/MIRRORS
1. No radios permitted. Anyone caught with driver/crew communication will be disqualified.
2. Mirrors permitted.
ENGINE
1. Any American made engine may be used as long as rear of engine (bell housing flange) is mounted at
least 72” forward from center line of the rear axle. Engine offset = no more than 2” from center of
cross member. Engine height minimum will be 11” from ground to front center of crankshaft.
2. Any engine used in competition must have been available in conventional passenger cars. No machine
work allowed on outside of engine block. Crate engines permitted.
3. No aluminum engine blocks.
4. All cars must use a wet sump oiling system. All oil pumps must mount in stock location on block.
5. No vacuum pumps.
ASPIRATION:
1. Any two (2) or four (4) barrel carburetors .
2. Must be naturally aspirated.
3. No fuel injection.
4. No electric fuel pumps.
5. No magnetos.
TRANSMISSION:
1. Only OEM production type transmissions allowed 3 speed, 4 speed, or automatic.
2. No "in and out" boxes.
3. Transmission must be clutch operated.
4. From standing position, driver must be able to engage car in gear and move
forward and then backwards-at any time.
5. Clutch type transmission must be equipped with an explosion proof steel bell housing.
6. After market multi-disk allowed. 5" minimum diameter.
7. All cars must be self-starting.
DRIVE SHAFT
1. Drive shaft loop is required and must be constructed of at least ¼ “ by 2” inch steel and should be
mounted no more than 6” from the front of the drive shaft.
2. The Drive shaft must be painted white.
3. No aluminum drive shafts.
REAR END:
1. Any passenger car type rear end may be used.
2. Quick change rear end allowed. Center section and side bells may be aluminum. Axles and tubes
must be steel.
EXHAUST:
1. Exhaust system must be mounted in such a way as to direct spent gases away from the cockpit of the
vehicle and away from any fuel sources.
STEERING / BRAKES:
1. O.E.M steering box only. No rack and pinion allowed.
2. No center steering.
3. No aluminum steering components.
4. (4) wheel working brakes required.
FUEL CELL:
1. Maximum of 22 gallon fuel cell mandatory. Fuel cell must be in 22 gauge steel container. Minimum
fuel cell to ground clearance = 8 inches.
ROLL CAGE:
1. Must consist of continuous hoops not less the 1.666” outside diameter and must have a wall
thickness of at least .095.
2. Must be frame mounted at no less than six (6) points.
3. Must consist of a configuration of front and rear hoops connected by tubing on the sides or side
hoops. Drivers head must not protrude above the cage with helmet and strapped in the drivers seat.
4. Low carbon, mild steel tubing is recommended. No brazing or soldering allowed.
5. Protection of feet is mandatory. Bar across back of engine with vertical bars and rub rails, or similar
protection.
6. No brace bars forward of cage may be higher than stock hood height.
7. Driver door bars must be as parallel with the ground as possible and located perpendicular to the
driver as to provide maximum protection for the driver, but without causing undue difficulty in
getting into or out of the vehicle. The side door bars must be welded to the front and rear of the roll cage
member.
BUMPER:
1. Bumpers must be used front and rear. No sharp edges permitted.
2. Front bumper must be mounted frame end to frame end with the bottom loop parallel to the ground.
Must be made of a minimum of 1 ¼ “ tubing and must be able to support the car if lifted by the
wrecker.
3. Rear bumper, nerf bars, and bodies must not extend beyond the width of the tires.
4. Rear bumper must protect the fuel cell.
5. Front and rear bumpers must have minimum 18” ground clearance. Measured in center.
WHEELS / TIRES:
1. Maximum overall track width (front or rear) shall not exceed 78 inches from outside of the tire right
side to outside of the tire left side. Maximum ½ “ spacer between hub and wheel. No wheel adapters
allowed. No tire warmers or air bleeders.
2. Steel racing wheel only. Maximum 8" wheel width.
2. Tires are to be Track Approved.
The track reserves the right to add weight at its discretion in the fairness of competition.
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