top of page


Mr. John Smith

Job title



Research and/or Engineering Questions/Objective: The NVH quality of automobile friction brake systems is highly important. Self-excited creep groan phenomena are critical in that field. The underlying low-frequency stick-slip of the friction pair occurs for cars with electrified powertrains and/or automated driving features in particular. In order to develop remedial measures, typical creep groan vibration patterns are also of interest. To this end, time-discrete ODS analyses have been performed. Methodology: A double wishbone axle setup including fixed calliper brake system has been investigated at a vehicle corner test rig. Machine and facility enable reproducible test matrix combinations of brake pressure and drum velocity under defined environmental conditions. The conducted ODS methods rest on two accelerometer allocations. One sensor arrangement was focussed on axle and suspension components, the other one on brake parts. In addition, the disk rotation has been captured in a fine incremental resolution. In order to realise a mechanical sensitivity study, two alternative upper control arm types were tested in terms of creep groan. Results: A large number of the test matrix combinations give birth to brake creep groan phenomena. The manifested stick-slip cycles are within typical fundamental frequency spans below 25 Hz and from 60 to 100 Hz. The upper control arm rubber bushings have an impact on the higher stick-slip frequency which shifts approximately 30 Hz here. The lower control arm bushings rather affect the bottom stick-slip frequency span instead. Exemplary ODS visualisations reveal specific non-linear component movements in dependence of current operational parameters. Thus, influences of local elasticities and/or subsystem resonance effects can be identified and global phases of stick or slip can be deduced. Limitations of this study: The study considers sustained creep groan. Triggering events as well as charging periods, which may also be of interest, are not investigated. Furthermore, limited numbers of sensors and data acquisition channels led to two separate arrangements with restricted spatial resolutions. All solid (metal) parts are assumed to interact as rigid bodies with geometric and/or flexible joints. It is noted that stick-slip of the friction pair is interpreted in a macroscopic sense here. What does the paper offer that is new in the field in comparison to other works of the author: A former work shows time-discrete ODS orbits at brake module level. The current publication includes also the axle and suspension system. Another creep groan related work treats bushing parameters in simulations. The present paper involves a real world component study instead. Conclusion: This study treats experimental creep groan investigations at automobile front corner level. The customised ODS analyses reveal underlying mechanisms as well as stimulated feedback resonances in an illustrative way. All visualisations agree with the authors’ subjective hands-on perceptions. Eventually, the influence of axle bushing properties is highlighted.

Manuel Pürscher, 1Institute of Automotive Engineering, Graz University of Technology, Austria; Peter Fischer

Operating Deflection Shape (ODS) of Fixed Calliper Brake and Double
Wishbone Axle During Creep Groan at Corner Test Rig

EB2019-FBR-021 • Paper • EuroBrake 2019 • Fundamentals of Braking Technology (FBR)


Sign up or login to the ICC to download this item and access the entire FISITA library.

Upgrade your ICC subscription to access all Library items.

Congratulations! Your ICC subscription gives you complete access to the FISITA Library.


Retrieving info...

Available for purchase on the FISITA Store


bottom of page