Extending the Lifespan of Tires

1. Extending the Lifespan of Tires By Shmuel L. Weissman and Jerome L. Sackman Symplectic Engineering Corporation and David Gillen and Carl L. Monismith Institute for Transportation Studies University of California, Berkeley

2. Overview • Motivation • Factors contributing to tire life • Proposed strategies

3. Motivation (Cont.) Extending the lifespan of tires: • is the best approach from an environmental standpoint. • is the largest contributor to reducing the number of scrap tires. • Problem: Tire life increase is leveling off. • Objective: Identify ways to extend tire life

4. Factors Contributing to the Average Lifespan of Tires • Maintenance • Original Equipment (OE) tires • Road condition and design • High performance tires • Budget tires

5. Other: ~1% of removals Oxidation and Separation: ~10% of removals Road Hazard: ~11% of removals Abnormal Wear: ~50% of removals Nothing Observed: ~9% of removals Normal Wear: ~19% of removals Tire Maintenance Causes for discarding tires (Source: Michelin).

6. Tire Maintenance • Alignment • Rotation • Tire inflation pressure

7. Tire Inflation Pressure “Under-inflation is tire’s #1 Enemy.” (Source: RMA) “Air pressure - Nothing else is more important.” (Source: Michelin) “Improper inflation pressure may result in rapid or irregular wear.” (Source: Bridgestone-Firestone)

8. Tire Inflation Pressure (Cont.) • National Highway and Traffic Safety Administration (NHTSA) survey found that, on average, tires are inflated to 6.1 psi below placard. • NHTSA compared hot pressure to placard, which is intended as cold pressure. Tires are actually inflated, on average, ≈10 psi below placard.

9. Tire Inflation Pressure (Cont.) • For each psi below placard, tires lose 1.78% of their tread life (Source: Goodyear). • Example: a tire with an 80K-mile limited warranty, maintained at 10 psi below placard, would lose 14K miles of its tread life.

10. Proposed Strategies • Technology: Auto-inflate systems • Public education • Corporate average tire life • Ad-valorem tire disposal tax/rebate

11. Strategy 2: Public Education Educate the public to: • Better maintain its tires • Purchase longer life tires

12. Strategy 2 (Cont.) • Advantages • Relatively inexpensive • Little opposition (both RMA and car producers advocate proper tire maintenance) • Addresses existing vehicles • Disadvantages • Not very effective in extending the average life mileage of tires (NHTSA survey results)

13. Strategy 2 (Cont.) Contribution to extending tire life

14. Strategy 2 (Cont.) • Present value of benefit: $1.6B • 5% probability of meeting or exceeding the projected benefit. • Conclusion: should be pursued, but in conjunction with other strategies.

15. Strategy 1: Technology: Auto-Inflate Systems • Concept: automatically maintain air pressure at placard level (adjusted for temperature). • Assumption:Introduced only as OE with new vehicles.

16. Strategy 1 (Cont.) • Advantages • A reliable way to maintain proper tire pressure • Maximize tire life • Improves safety • Improves fuel economy • Reduces air pollution • Applicable to both light and heavy-duty vehicles

17. Strategy 1 (Cont.) • Disadvantages • Increases the upfront cost of new vehicles • Requires maintenance (e.g., replacing batteries every 10 years) • Automakers may oppose (the Alliance of automakers lobbied strongly to allow indirect TPMSs in the NHTSA rule)

18. Strategy 1 (Cont.) Contribution to extending tire life

19. Strategy 1 (Cont.) • Benefit/Cost ratio: 1.24 • Net present value: a profit of $1B • 60% probability of meeting or exceeding the projected NPV. • Conclusion: Highly effective and reliable strategy that also improves safety and fuel-efficiency, and reduces air pollution.

20. Strategy 1 (Cont.) Implementation options • Educating the public to demand auto-inflate systems with new vehicles • Mandating a phased-in introduction of auto-inflate systems in new vehicles over a number of years (similar to the TPMS rule)

21. Thank you • Questions?