Editorial Type:
Article Category: Research Article
 | 
Online Publication Date: 01 Dec 2009

Laboratory Measurement of Tire Flatspot3

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Page Range: 279 – 301
DOI: 10.2346/1.3251344
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Abstract

Tires flatspot when they remain loaded without rolling for a period of time. The magnitude of this flatspot and the speed with which it recovers due to subsequent rolling are influenced by the temperature and load histories. Experience indicates that controlled measurement in the laboratory is the best way to measure the flatspot characteristics of tires. However, the laboratory test procedure must be based on the flatspot and recovery conditions the tire experiences in the field for the measurements to truly represent tire performance. Processing of the experimental data to compute the initial flatspot and its decay due to rolling also requires special care since the flatspot decays from the first revolution of the tire after flatspot. Effects of flatspot on a tire can be measured in many ways using low or high speed uniformity measurements or by measuring the radial runout of the tire.

This paper will address the issues involved in flatspot measurement of tires and also present mechanistic explanation of the influence of test conditions on flatspot.

Keywords: flatspot; radial runout; radial force variation; RH1; RH2; tread scan
Copyright: The Tire Society
FIG. 1.
FIG. 1.

(a) Schematic of a typical tire flatspot. (b) Color map of a flatspotted tire. (c) Initial and flatspotted scan lines at the dashed line in (b).

FIG. 2.
FIG. 2.

Typical vehicle service situations cause tire flatspot.

FIG. 3.
FIG. 3.

Typical tire flatspot conditions.

FIG. 4.
FIG. 4.

Mechanics of flatspot formation—a simplified illustration.

FIG. 5.
FIG. 5.

A general procedure for tire flatspot testing.

FIG. 6.
FIG. 6.

Computation of flatspot by subtraction of initial uniformity from flatspotted uniformity.

FIG. 7.
FIG. 7.

Influence of temperature and duration on flatspot and potential test conditions.

FIG. 8.
FIG. 8.

(a) Tire radial harmonic magnitudes during flatspot testing. (b) Tire radial harmonic phase angles during flatspot testing.

FIG. 9.
FIG. 9.

(a) Tire fore-aft harmonic magnitudes during flatspot testing. (b) Tire fore-aft harmonic phase angles during flatspot testing.

FIG. 10.
FIG. 10.

Strategies for subtracting initial tire uniformities to compute flatspot.

FIG. 11.
FIG. 11.

(a) Regression of flatspot reduction data. (b) Regression of flatspot reduction data (first five minutes).

FIG. 12.
FIG. 12.

Influence of temperature and Inflation on transportation induced flatspot.

FIG. 13.
FIG. 13.

Influence of inflation on long term storage flatspot.

FIG. 14.
FIG. 14.

Influence of tire temperature on parking lot flatspot.

FIG. 15.
FIG. 15.

Mechanistic explanation of tire temperature influence on parking lot flatspot.

FIG. 16.
FIG. 16.

Correlation between low speed uniformity measurement and radial runout.

FIG. 17.
FIG. 17.

Influence of tire break-in on initial flatspot.

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