USTMA Temperature Sensitivity Analysis and Surface Validation Data 11 June 2018 Daniel Christ Sr. Traction Performance Engineer Michelin Americas Research Center

Key Questions 1) Temperature range in San Angelo TX. (Slides 4-5)  2) Justification for third category (US A/S) (Slides 6-17) Recommendations from 2016 were based within the current R117 framework.   3) Is San Angelo Track in the R117 window? (slides 18 -19) Only Temperature addressed in this presentation.

Temperature Sensitivity analysis utilizing the USTMA Temperature study data Three processing methods were considered: “Unadjusted” - No temperature or surface grip level adjustment (a & b = 0). However, this presentation is only intended to comment on temperature effects. The grip compensation could still be applied if desired (b=?) “Normal” - Standard Summer tire compensation as specified for “Normal” tires in R117 (a=-0.4232, b=-8.297) “Snow” - Standard winter tire compensation as specified for “Snow” tires in R117 (a=0.7721, b=33.18)

The R117 “Snow” Tire Test Window Limits Testing Season (imagine snow campaigns for grading) San Angelo, Texas R117 “Snow Tire” Test Window 5+ Months of being unable to test 2013 Data provided by NOAA’s KSJT station in San Angelo, Texas

The R117 “Normal” Tire Test Window is Better for A/S Tires San Angelo, Texas R117 “Normal Tire” Test Window R117 “Snow Tire” Test Window 5+ Months of being unable to test 2013 Data provided by NOAA’s KSJT station in San Angelo, Texas

Is Temperature sensitivity different for A/S tires compared to other categories? 3PMSF Unadjusted Linear Fits Used

“Normal” Summer tires have more natural temperature sensitivity than A/S tires in their usage temperature window Note: UHP A/S Slope (shown on both plots) is somewhere between A/S tires (with zero slope) and UHP (“Normal”) tires

More slope after adjustment The “normal” temperature window is more relevant than the “snow” window for All-Season tires, but the “normal” tire processing imparts an additional temperature sensitivity in the WGI for A/S tires Slightly less slope for UHP A/S also “Normal” Temp Window >1 Bin Less slope after adjustment More slope after adjustment

More slope after adjustment Treating A/S tires as “Normal” Pros: Appropriate temperature window Cons: Imparts additional temperature sensitivity “Normal” Temp Window >1 Bin More slope after adjustment

“Snow”* Tires show similar temperature sensitivity as A/S tires when left unadjusted but at a lower wet grip level These are M+S and 3PMSF - Severe Snow when discussing Tire selections * Note: Snow Category Includes M+S and 3PMSF, but all “Snow” tires here are 3PMSF

“Snow” Correction imparts unnatural boost to all data potentially to utilize the same grading scale as “Normal” tires More slope after adjustment “Snow” Temp Window “Snow” Temp Window ~1 Bin More slope after adjustment * Note: Snow Category Includes M+S and 3PMSF, but all “Snow” tires here are 3PMSF

More slope after adjustment Treating A/S tires as “Snow” Pros: Alignment with current R117 “M+S”=“Snow” categorization Cons: Imparts additional temperature sensitivity + Restricted Window “Snow” Temp Window ~1 Bin More slope after adjustment

So which do we choose? Neither is really acceptable for A/S tires! >1 Bin “Normal” Temp Window More slope after adjustment ~1 Bin “Snow” Temp Window More slope after adjustment

What is needed is a third category somewhere in between that is designed specifically for A/S tires >1 Bin More slope after adjustment <1 Bin ~1 Bin “Snow” Temp Window More slope after adjustment “Normal” Temp Window “Normal” Temp Window

[2016] Recommendation for A/S tires “Normal” Temp Window <1 Bin Full temperature range Does not limit testing capabilities in US Is representative of usage conditions No temperature Correction a = 0, b = ? If an equation was developed for A/S tires we expect a ~= 0

3 Recommended Categories [2016] “Snow” Temp Window “Normal” Temp Window “Normal” Temp Window

ETRTO Round Robin Data for A/S tires shows similar trends and confirms the recommendation to not use a temperature correction for A/S tires

Characterizing USTMA Tracks 14”SRTT and Sand Depth

Could we look directly at the 16” SRTT They tell us essentially the same thing USTMA Tracks USTMA Tracks Water Depth Range: 1-1.27mm

Conclusions A/S tires are different than Normal and Snow tires Recommendation for A/S tires: [2016] Full temperature range Does not limit testing capabilities in US Is representative of usage conditions No temperature Correction a = 0, b = ? If an equation was developed for A/S tires we expect a ~= 0