Rules Addendums and Clarifications

TECHNICAL BULLETIN 4-28-18

ST4/TT4 and ST5/TT5 Hoosier DOT Wet Tires

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ST1-4 Rules
6.4.1 ST4 Tire Limitations1) Compound
Non-DOT approved tires are not permitted in ST4. DOT-approved R-compound autocross tires
shall be assessed via the “Adjusted Weight/Power Ratio” in ST4.
Hoosier DOT Wet tires shall be assessed as autocross tires except during officially designated
“Rain Sessions” when they may be used without a Modification Factor assessment.

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ST1-4 Rules
6.5.2 Modification Factors
Tire TypeST4 Only: DOT-approved R-comp Autocross tires = -1.0
(examples: A6, A7, DOT Wet, R1S, RS AC, Z214-C90/91)

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ST5 Rules
6.1.2 Tire Limitations1) Compound
1) Tire treatments and softeners are not permitted.
2) Non-DOT approved tires are not permitted in ST5.
3) DOT-approved R-compound autocross tires (“A-tires”) are not permitted in
ST5. (examples: A6, A7, DOT Wet, R1S, RS AC, Z214-C90/91)
Hoosier DOT Wet tires shall be permitted ONLY during officially designated “Rain Sessions”