T6.3.3 Standard wheel lug bolts are considered engineering fasteners and any modification will be subject to
extra scrutiny during technical inspection. Teams using modified lug bolts or custom designs will be
required to provide proof that good engineering practices have been followed in their design.
T6.3.4 Aluminum wheel nuts may be used, but they must be hard anodized and in pristine condition.
T6.4 Tires
T6.4.1 Vehicles may have two types of tires as follows:
a. Dry Tires – The tires on the vehicle when it is presented for technical inspection are defined as
its “Dry Tires”. The dry tires may be any size or type. They may be slicks or treaded.
b. Rain Tires – Rain tires may be any size or type of treaded or grooved tire provided:
i. The tread pattern or grooves were molded in by the tire manufacturer, or were cut by
the tire manufacturer or his appointed agent. Any grooves that have been cut must have
documentary proof that it was done in accordance with these rules.
ii. There is a minimum tread depth of 2.4 mms (3/32 inch).
NOTE: Hand cutting, grooving or modification of the tires by the teams is specifically prohibited.
T6.4.2 Within each tire set, the tire compound or size, or wheel type or size may not be changed after static
judging has begun. Tire warmers are not allowed. No traction enhancers may be applied to the tires
after the static judging has begun, or at any time on-site at the competition.
NOTE: Due to the hazardous nature (significant health effects) of some traction modifier ingredients,
teams are advised to closely follow manufacturers recommended procedures for safely handling and
use of traction modifiers, if used before competition.
T6.5 Steering
T6.5.1 The steering wheel must be mechanically connected to the front wheels, i.e. “steer-by-wire” or
electrically actuated steering of the front wheels, is prohibited.
T6.5.2 The steering system must have positive steering stops that prevent the steering linkages from locking
up (the inversion of a four-bar linkage at one of the pivots). The stops may be placed on the uprights
or on the rack and must prevent the tires from contacting suspension, body, or frame members during
the track events.
T6.5.3 Allowable steering system free play is limited to seven degrees (7°) total measured at the steering
wheel.
T6.5.4 The steering wheel must be attached to the column with a quick disconnect. The driver must be able
to operate the quick disconnect while in the normal driving position with gloves on.
T6.5.5 Rear wheel steering, which can be electrically actuated, is permitted but only if mechanical stops limit
the range of angular movement of the rear wheels to a maximum of six degrees (6°). This must be
demonstrated with a driver in the car and the team must provide the facility for the steering angle
range to be verified at Technical Inspection.
T6.5.6 The steering wheel must have a continuous perimeter that is near circular or near oval, i.e. the outer
perimeter profile can have some straight sections, but no concave sections. “H”, “Figure 8”, or cutout
wheels are not allowed.