SM Wet Tire
#26122 from Spec Miata Committee · Recommended to the Board · Minutes (2019-02 Fastrack)
In SM, GCR Section 9.1.7.C.5, make changes and add new section as follows:
Wheels/Tires
“Any wheel/tire may be used within the following limitations:
a. Required rim diameter is fifteen (15) inches. Maximum rim width is seven (7) inches.
Minimum weight of wheel shall be 13 lbs without spacers. All four wheels must be the same
dimension including offset.
b. All wheels must be one-piece metal castings (not multi-piece wheels, bolted, riveted or
welded together).
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c. Tires 1. Regional and Majors CompetitionAll cars shall use the P205/50ZR15 Hoosier “SM7” Spec Miata Dry or the P205/50R15Hoosier “H2O” Spec Miata Wet tires.
c. The front track shall not exceed 1450 mm. The rear track shall not exceed 1475 mm as
measured per Appendix G, Measuring Track.
d. Aftermarket wheel studs, lug nuts, and wheel spacers are permitted. If spacers are used
they shall be no greater than 13mm and equal per axle.
e. Tire tread (that portion of the tire that contacts the ground under static conditions) shall not
protrude beyond the fender opening when viewed from the top perpendicular to the ground.
To determine compliance, the vehicle should be rolled through a powdered substance, as
raced with driver, in order to indicate the tire tread contact patch under static conditions.”
“6. Tires
Competitors must use the official SM Dry tire or SM Wet tire for Regional and Majors
competition.
a. Tires must be used in complete sets. No mixing of wet and dry tires on the car.
b. Dry: P205/50ZR15 Hoosier SM7. Required for all cars Regional and Majors competition.
c. Wet: P205/50R15 Hoosier SMW.
1. Majors competitors may use either the 205/50R15 Hoosier H2O or the 205/50R15 Hoosier
SMW up until June 2nd, 2019. Effective June 3rd, 2019 all Majors/SuperTours competitors
must use the 205/50R15 Hoosier SMW.
2. Regional competitors may use either the 205/50R15 Hoosier H2O or the 205/50R15
Hoosier SMW.
3. In 2020 all Regional and Majors competitors will be required to use only the 205/50R15
Hoosier SMW wet tire.”