Volume 44, No 1, 2022, Pages 123-131

Download full text in PDF

An Experimental Study of Forced Vibration Influence on Disc Brake Drag Torque in Heavy Commercial Road Vehicles


Pontus Fyhr , Rikard Hjelm , Jens Wahlström

DOI: 10.24874/ti.1132.06.21.09

Received: 10 June 2021
Revised: 15 July 2021
Accepted: 11 September 2021
Published: 15 March 2022


Drag torque in a disc brake is the residual torque when the brake is not activated. This torque can adversely influence the total energy consumption, life of the brake components, and level of airborne wear particles from vehicles. Drag torque is of special interest for long haul trucking since it could have an effect of the total energy consumption. Drag torque performance of a disc brake is usually evaluated with conventional inertia dynamometers. Vibrations induced by the wheel can help to retract the pads from the disc and decrease the drag torque. It is hard to study this phenomenon with conventional inertia dynamometers since there is usually no system to induce a forced vibration on the brake. Therefore, the aim of the paper is to investigate the effect of vibrations on the drag torque for a commercial vehicle disc brake with a novel test setup. This is done by comparing test run with and without pads, forced vibrations, and pad retraction springs. The results indicate that the forced vibrations strongly affect the level of measured drag torque. In addition, the introduction of a retraction spring can reduce drag torque with more than 50% when vibrations are induced.


Drag torque, Disc brake, Testing vibrations, Heavy commercial vehicles

Latest issue


Volume 46
Number 2
June 2024

Crossref logo


TiI news RSS 2.0

Table of contents