Control of brake drag is an important disc brake corner OEM requirement to minimize brake judder, friction material temperatures and fuel consumption. Brake calipers usually include clearances between the pads and rotor during brakes-off running conditions, allowing the pads to be knocked clear of the rotor; therefore minimizing drag. The present paper describes test methods to validate caliper designs, data analysis techniques to diagnose drag problems and data sets with worked examples.
The present study summarizes the results of over 300 dynamic drag tests incorporating 60 separate test samples. The test samples share the same vehicle platform design; however three variations of Standard production design, Standard production design plus a pad spreader shim and a design with increased retraction are included. The effect of these design variations on drag is presented, whilst the effect of adding an adhesive to a pad back plate is also indicated. A most significant observation was discovered when re-testing the samples after 18 months of storage which indicated a significant reduction in drag knee-point.