ISO 28580:2018 — Tyre Rolling Resistance Measurement: Single Point Test and Correlation Methods

Introduction to ISO 28580

ISO 28580:2018 specifies laboratory methods for measuring tyre rolling resistance under controlled conditions for passenger car, truck, and bus tyres. The standard has been technically revised from the 2009 edition, incorporating clarifications, an expanded reference machine concept (physical or virtual), improved alignment procedures, and machine drift evaluation. Rolling resistance directly impacts vehicle fuel efficiency — a 10 % reduction in rolling resistance can improve fuel economy by 2-3 %. For a long-haul truck travelling 200,000 km per year, this translates to thousands of litres of fuel saved and a corresponding reduction in CO₂ emissions.

Test Methods and Equipment

The standard defines both force and torque measurement methods using a steel drum apparatus. The tyre runs against a rotating drum of specified diameter (typically 1.707 m or 2.0 m for passenger tyres, with larger drums for truck tyres). Four measurement methods are permitted: force method at tyre spindle, torque method at drum axis, power method at drum axis, and deceleration method. Each method has distinct advantages in terms of accuracy, cost, and complexity. The force method is the most direct and commonly used, measuring the horizontal reaction force at the tyre spindle using a precision load cell.

Parasitic Loss Correction

A critical aspect of rolling resistance measurement is accounting for parasitic losses — energy consumed by bearing friction, aerodynamic drag of rotating components, and other systematic losses not attributable to the tyre itself. The standard describes three methods: skim test reading (reducing load until tyre losses approach zero), deceleration method (measuring system inertia and deceleration), and computational subtraction. The skim test involves running the tyre at a very low load — typically 100 N or less — and measuring the residual force, which represents the parasitic component.

Temperature and Drum Diameter Correction

Rolling resistance decreases as tyre temperature increases. The standard specifies temperature correction algorithms to normalize measurements to reference conditions (25 °C). A typical correction factor is approximately 0.6 % change in rolling resistance per degree Celsius. Similarly, drum diameter correction adjusts results from non-standard drums to the reference diameter, as smaller drums induce higher deformation and artificially higher rolling resistance values.

Engineering Design Insights

The 2018 revision introduced the concept of a “virtual reference machine” — a group of machines whose aggregated results serve as the alignment benchmark. This innovation allows smaller laboratories without access to a physical reference machine to achieve comparable results through collaborative alignment. The alignment procedure uses “alignment tyres” — stable reference tyres measured by both candidate and reference machines — and computes correction coefficients that account for systematic differences between machines.

Machine drift evaluation (Annex F) requires laboratories to regularly monitor their measurement stability using laboratory control tyres. A machine showing drift beyond defined limits must be investigated before further alignment testing can proceed. This quality assurance framework mirrors ISO 17025 laboratory accreditation requirements and ensures that rolling resistance measurements remain comparable across time, machines, and laboratories.

Frequently Asked Questions