Development of an Accelerated Laboratory Test to Simulate Real-World Tire Flat-Spotting 2019-01-1509
Tire flat-spotting occurs when tires remain in a loaded condition without rolling for an extended period of time, and can be temporary or permanent depending on the length of storage, vehicle loading and environmental factors. Tire non-uniformity caused due to flat-spots often induce shake and shimmy vibration in vehicles due to increased tire-wheel force variation input into the chassis. This results in increased warranty costs for OEMs / tire suppliers and customer dissatisfaction in third-party quality surveys such as J. D. Power IQS. Flat-spotting is of particular concern for slow-moving vehicle inventory that remains parked for long periods at OEM plants and/or dealership lots.
OEMs often stipulate or recommend inventory storage practices for dealers that require physical movement of vehicles every 30 days to reduce the risk of tires developing permanent flat-spots. OEMs also provide component level flat-spotting requirements to tire manufacturers during sourcing and specification timing to secure their internal requirements and targets. The study in this paper initially determined real-world flat-spotting levels on an actual vehicle during the adverse summer months of Arizona. Tire uniformities measured on a high-speed uniformity machine were used as an indicator of flat-spotting performance. Using an environmental chamber and custom designed loading fixtures, appropriate loads and temperatures were applied simultaneously to develop an accelerated test criteria that duplicated real-world flat-spotting behavior.
The study outlined in this paper developed a two-day test using equivalent vehicle loading and elevated temperatures that produced the equivalent tire flat-spotting of a 30-day real-world storage during adverse summer conditions. This accelerated test allows a quick evaluation of tire flat-spotting performance that can be expected in adverse real-world conditions. Over the long term, it is estimated that such testing will generate more precise specifications for tire manufacturers, drive better inventory management and storage practices, reduce warranty costs and improve customer satisfaction.
Farokh Kavarana, Scott Fritz
NissanTechnical Center North America, Nissan Technical Center North America
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