Improvement of Tire Development Process Through Study of Tire Test Procedure and Vehicle Correlation 2018-01-1337

The tire is the vital element in vehicle dynamics, as its contact patch transmits all forces and moments to the ground (accelerating, braking, cornering, rolling).Over the recent decades tire development for passenger cars has been continuously improved and optimized in order to achieve a good overall vehicle performance in R&H that is in balance with all other tire performances (Wear, Durability, NVH, RR, Miles). This general development process has to be suitable for various vehicle types from regular passenger cars over eco-friendly hybrid or electric vehicles to high performance sport cars. The balance between Ride and Handling performance is further adjusted to local customer preferences that are usually distinguished by markets (US, EU, Asia).

The tire development process, which is embedded in the overall vehicle development, is usually realized in a mutual collaboration between OEM and tire supplier.

This process starts with the definition of tire performance targets, which are regularly checked and aligned with the overall vehicle performance during the development phase until the final joint evaluation that confirms the target achievement level at end of the development.

There are two evaluation methods for tire performance:

• subjective evaluation of R&H performances from full vehicle experiments
• objective measurements from subcomponent and full vehicle experiments.

In detail of tire evaluation, tire performances are historically evaluated during subjective test drives on R&H manoeuvers/tracks. The subjective evaluation could show a level of both good and bad, but it is not easy way to keep a consistency of evaluation and guide a clear direction of improvement depend on evaluator’s skill level and external effects such as road condition and weather condition.

Objective measurements that represent realistic driving conditions could be used to make the development process more robust and support the initial target setting and guarantee coherence of evaluation throughout the entire process.

This paper goal is to expand objective evaluation’s contribution into the tire development process. For it, the test of objective evaluation should be reliable to represent realistic driving conditions, repeatable for repetition test, robust for noise effect which would be happen during test. And tire characteristics values from extracting force and moment of tire have to get a good correlation with vehicle handling performances. Then objective evaluation could be used more active in the tire development process than before. This paper would like to introduce what kinds of activities are necessary to be reliable tire test measurement and how to prove the correlation between tire characteristics and vehicle performance.

In the following studies four improvements of the objective measurements and their extracted key characteristics have been achieved. The first improvement focused on tire measurements, by applying realistic conditions for pretest and measurements of tire characteristics. The second dealt with the alignment of measurement procedures between OEMs and tire makers. In order to establish robust standards that can be evaluated in terms of measurement repeatability and deviation. The third improvement was a large study of correlation between tire characteristics and vehicle performances; using simulation. And the last improvement consisted of storing tire characteristics values in a centralized database in order to set robust tire targets, based on performance prediction and continuous quality control.

The above mentioned improvements of test procedures and key characteristics, have increased pace and efficiency of the tire development process.