Editorial Type:
Article Category: Other
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Online Publication Date: 01 Jul 2014

Average Worn Profile of Tires in Europe

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Page Range: 166 – 184
DOI: 10.2346/tire.14.420303
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ABSTRACT

Tire tread wear is a key issue in the tire development process and for tire customers. In order to measure the wear performance, tire manufacturers usually proceed to wear tests and calculate the tire life from those tests. An important point in this tire life computation is the criteria chosen for defining the tire's end of life. In Europe, there is a legal minimum tread depth set to 1.6 mm applicable to 75% of the tread pattern width. However, outside those 75% (i.e., on the shoulder part), no clear and shared limit is defined. Also, the usual behavior of customers to decide when their tires should be changed is not well known. The goal of this 2012 study was to identify an average worn profile of tires in Europe and the behavior of customers for replacing their tires. For that, 3000 tires worn out by customers have been collected in scrapyards and measured in five European countries. In this article, we will present the tire collecting method, the measurement process, the analysis method, and some general results and statistics on this 3000 tire database. Finally, the method to compute the average end of life profile and the resulting profile is given.

Keywords: tire wear; worn profile; shoulder wear; scrap tire; wear bar
FIG. 1
FIG. 1

Statistical distribution of tread depth in the center in scrapyard, on 5249 tires measured across 21 countries in Europe in 2012.

FIG. 2
FIG. 2

Statistical distribution of tread depth in the center, comparison without selection (5249 tires across 21 countries) and with selection on the wear level (our study on worn profile, 2946 tires across five countries).

FIG. 3
FIG. 3

Example of the location of the tread depth gauge measurement points, for shoulder and center part. The illustration is given on a laser measured profile.

FIG. 4
FIG. 4

Pantograph tool (top) and operating method to find the tread center (bottom).

FIG. 5
FIG. 5

Distribution of the tires by tire size.

FIG. 6
FIG. 6

Distribution of the tires by manufacturing year. Note that the tires were collected in scrapyards during the spring 2012.

FIG. 7
FIG. 7

Distribution of the brands by group (left), and brand distribution (right).

FIG. 8
FIG. 8

Estimated by a Michelin wear expert: main wear removal cause of the tires (left) and irregular wear statistics (right).

FIG. 9
FIG. 9

Wear obliquity, computed by the linear slope of the remaining tread depth. The value indicated is the difference of tread depth with this slope, for 100% of the ETRTO tread width. Only the asymmetric tires have been used, to differentiate vehicle interior and exterior sides.

FIG. 10
FIG. 10

Percentage of the tread width covered by tread wear indicators (TWI), the tread width is defined through the ETRTO formula.

FIG. 11
FIG. 11

Illustration of the database content, with all the laser measurements (1 point out of 10 for readability) and five randomly selected worn profiles, showing the variety of tires collected.

FIG. 12
FIG. 12

Average worn profile of collected tires, by removal cause and for all tires together.

FIG. 13
FIG. 13

Comparison between an expert “human” classification (center, normal, shoulder wear) and an objective one (based on a quadratic fitting of the worn profile).

FIG. 14
FIG. 14

Deciles of worn profiles, from 10% (less worn) to 90% (most worn) by step of 10%, for all removal causes.

FIG. 15
FIG. 15

Examples of translation of worn profiles to a legally reasonable end of life profile.

FIG. 16
FIG. 16

Worn profile examples, for center wear and normal wear.

FIG. 17
FIG. 17

Worn profile when splitting the database in left and right obliquities. Normal and shoulder worn tires together. For comparison, the average of shoulder wear tires (with no obliquity filtering) is plotted.

FIG. 18
FIG. 18

Linear regression of the resulting profile after the four steps, for left and right shoulder.

FIG. 19
FIG. 19

Definition of the end of life customer profile.

FIG. 20
FIG. 20

Synthesis of the customer end of life limit.

FIG. 21
FIG. 21

Example of use of the end of life customer profile for wear testings.

Contributor Notes

2 Corresponding author. Email: frederic.biesse@fr.michelin.com. Phone: +33 (0)4 73 10 91 67
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