A pneumatic spring brake actuator , in particular a parking and service brake actuator for use in a commercial vehicle, said spring brake actuator comprising: - a housing comprising a housing base , - a spring brake piston accommodated at least partially in said housing , said spring brake piston being configured to reciprocatingly move between a retained position and an extended position along a longitudinal axis as a function of pressure inside a spring brake pressure chamber , - a compression spring located between the housing and the spring brake piston , said compression spring being effective to push the spring brake piston towards the extended position, characterized in that the spring brake piston comprises: - a service brake pressure chamber , - a piston chamber , and - a service brake piston separating the service brake pressure chamber from the piston chamber , wherein said service brake piston is configured to reciprocatingly move between a retained position and an extended position along said longitudinal axis as a function of pressure inside the service brake pressure chamber , wherein said spring brake piston comprises a front face , said front face being arranged opposite from said housing base , and a first pipe section extending from said front face towards said housing base , wherein said first pipe section radially limits said service brake pressure chamber and piston chamber , characterized in that the said spring brake piston comprises a second pipe section extending coaxially around said first pipe section , wherein said second pipe section comprises a radial protrusion abutting against a radial wall of said housing , wherein a volume between said second pipe section , said protrusion and said radial wall defines said spring brake pressure chamber . - a housing comprising a housing base , - a spring brake piston accommodated at least partially in said housing , said spring brake piston being configured to reciprocatingly move between a retained position and an extended position along a longitudinal axis as a function of pressure inside a spring brake pressure chamber , - a compression spring located between the housing and the spring brake piston , said compression spring being effective to push the spring brake piston towards the extended position, - a service brake pressure chamber , - a piston chamber , and - a service brake piston separating the service brake pressure chamber from the piston chamber , wherein said service brake piston is configured to reciprocatingly move between a retained position and an extended position along said longitudinal axis as a function of pressure inside the service brake pressure chamber , wherein said spring brake piston comprises a front face , said front face being arranged opposite from said housing base , and a first pipe section extending from said front face towards said housing base , wherein said first pipe section radially limits said service brake pressure chamber and piston chamber , characterized in that the said spring brake piston comprises a second pipe section extending coaxially around said first pipe section , wherein said second pipe section comprises a radial protrusion abutting against a radial wall of said housing , wherein a volume between said second pipe section , said protrusion and said radial wall defines said spring brake pressure chamber . <EOS>