Modified Class Rules

Modified Division:

**This class has a 16+ age requirement

**Fuel must not exceed 94 octane pump gas

Chassis:

• The mower must be of lawn tractor origin and built on a lawn tractor frame.

• The seat must be either bucket style to support the driver from side to side impact or can be of lawn tractor origin securely fastened to the frame and must have a right side support bar to keep the driver on the seat during cornering.

• Front and back tube style bumpers are mandatory, Bumpers must be bent or capped with no sharp edges or open gaps between tubes. Bent ends are preferred but capped flat bumpers are accepted as well as long as there are no sharp edges. The back bumper must have a hoop-style backguard to protect the driver from rear impact.

• Nerf bars are mandatory, they must offer sufficient protection to the driver's ankles. Tube-style design is mandatory. The gap between bumpers must be closed according to the tech director's discretion. Either sheet steel, plastic or expanded metal are some of the safe options to fill the nerf bars to avoid a driver getting their foot caught.

• Nerf bars can not protrude past the extremity of the tires and must not be recessed more than 1” from the outer face of the tires

• Front axles may be fabricated or reinforced but must be mounted in the original location, a one-piece design securely bolted or welded to the chassis. Utilization of original spindles is optional but must be a minimum of ¾” and a ⅝” minimum for kingpins. No plastic bushing for kingpins.

• Chassis can NOT be widened, narrowed, lengthened or shortened by any means. Discrete holes, notches or removable panels are accepted to facilitate the building/repairs on the chassis. Holes/notches will most likely be needed to retrofit a solid axle construction, implement a gearbox or installation of hydraulic braking system.

• The only chassis modification allowed is the lowering of the back tubular section of the body where the seat is to be mounted. It is preferred that all mowers be built to keep the driver as low as possible to the ground to eliminate any stability issues where they arise. 

• Cutting deck must be removed and it is highly recommended that the mower be lowered to at least a 4” ground clearance. The mower can be lower if preferred.

• Battery must be securely fastened to the tractor and the positive terminal must be covered with some sort of dielectric protector. No bungee cords. Industrial zip ties may be permitted with tech directors discretion.

Steering:

• Factory, direct, or custom steering is accepted at the tech director’s discretion.

• The steering wheel must be steel/aluminum, Plastic steering wheels will not be accepted.

• Direct steering is optional.

• Steering shafts, arms and bars must not be less than ½” as anything less has a strong chance of twisting/bending under load.

• Kingpins must be no less than ⅝” and spindles have to be ¾’ or above.

• Heim joints are mandatory on all steering linkages, a minimum of ⅜” 

• Spindles must have a “failproof” lock so wheels can not fall off during racing. Crown nut with a cotter pin is a common method used.

Wheels and tires:

• Turf tires are mandatory in all classes.

• Front rims 6” and rear rims 8”.

• Front rims and tires can be mounted on a bearing style rim that slides directly on a spindle, or a bolt-on rim to a bearing hub is a more preferred method as it increases the rigidity of the rim. 

• Stock lawn tractor rims with plastic or brass bushing will not be accepted. Cutting of tires will not be accepted.

• Golf cart steel rims and keyed shaft style lawn tractor rims are accepted although aluminum bolt-on style rims are preferred.

Drivetrain and Engine:

• Engine must be of lawn tractor origin, twin cylinder gasoline powered air-cooled engines are a must, no liquid-cooled type engines. Oil coolers are permitted.

• Engine modifications are not permitted in this class

• A tether-style kill switch is mandatory to shut the machine off in case of a rollover

• Belt or chain drive systems allowed, centrifugal clutch or direct clutch allowed.

• Any belt/chain drive systems must be sufficiently covered with a minimum ⅛” steel or aluminum to protect the driver and other racers.

• Engine must be governed at no more than 3850rpm with a steel flywheel. 

• Rear hydraulic brakes are optional but recommended and must be mounted to the rear axle. Original transaxle brakes or manual-style brakes can be utilized as long as it is mounted on the rear axle. All brake styles must completely lock up.

• The rear axle is to be made of a minimum 1” shafting unless utilizing an original transaxle. If shafting is bent or damaged it must be replaced and can not be fixed.

• Transaxle, transmission or 90-degree gearbox are all accepted in this class. 

• Spring return throttle is mandatory, and must be mounted on the footboard as an accelerator pedal.

• Mufflers are optional but exhaust must be safely routed out from under the hood and in a safe location (ie: under the running board, directly under the chassis, or out the back of the chassis).

• Axles can be widened up to 42” both front and rear.