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

2. 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 )
Only Temperature addressed in this presentation.

3. 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= , b=-8.297)
“Snow” - Standard winter tire compensation as specified for “Snow” tires in R117 (a=0.7721, b=33.18)

4. 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

5. 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

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

7. “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

8. 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

9. 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

10. “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

11. “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

12. 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

13. 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

14. 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

15. [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

16. 3 Recommended Categories [2016]
“Snow” Temp Window
“Normal” Temp Window
“Normal” Temp Window

17. 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

18. Characterizing USTMA Tracks 14”SRTT and Sand Depth

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

20. 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