Brake judder investigation requires the understanding of the vibration transmission paths that

define how the vibration energy generated by the fluctuating brake torque is transmitted to the

vehicle body through the suspension parts and the chassis. This knowledge allows a more

accurate characterisation of brake judder problems in vehicles and it is a general tool to identify countermeasures for reducing the vehicle body and chassis sensitivity to brake judder

excitation.

Judder Transfer Path Analysis (JPA) is an analysis tool that allows us to assess the possible

ways of energy transfer from the brake to a given target location in a vehicle. It supplies the

tools required to locate the most important energy transfer paths for a specific problem, and to

evaluate their individual effects on the target, thus providing valuable insight into the

mechanisms responsible for the problem.

The essential elements in the analysis of this type of problem are:

· The excitation sources: structure and/or airborne, acoustical or vibration. Typical

sources include the vibration of a car engine, road induced vibrations or suspension

loads generated during brake judder.

· The target locations: These are typically acoustical or vibration perceived by the driver

in a car during operational conditions. In our case we focus on the vibration perceived

by a driver during the occurrence of brake judder. The target points to assess the vehicle

performance in these circumstances normally are the brake pedal, the steering wheel

and the seat rail [1] [2] [3].

· The structural transfer paths which are represented by the physical mounts and/or rigid

connections whereby the noise and vibration are transferred from the source to the

target location. In our case, this transfer paths will be structural paths that transmit the

suspension vibration excitation into the chassis and body hard-points when the brake

exhibits judder

García, J.J, Calvo, O, Montané X, Ferrer B, Squadrani F, Applus+IDIADA; Santa Oliva, Tarragona, Spain; Faresin, M, Maserati S.p.A, Italy