Air Parking brake

[baby]

Hello I'm new to this forum I have 4 05 freightliners work mr2 bussines class mercedes engine.On one of them I found down when I press parking air brake truck still travel around 5 to 7 feet before parking brake kick on and stop truck.How can I adjust this parking brake or what can be wrong?Mine other 3 Freightliners truck stop and maybe move by half foot.Thank you for your help

[Dagwood]

baby if it is just the adjustment try your owners manual for instructions on adjusting. Bear in mind you can destroy the self adjusters if this is done improperly. When you pull the brake button out it removes air pressure from the brake and a spring will set the brake. Oh by the way welcome to IRV2.com.
PS It's only about a 10 minute job to adjust but a better question is why did the slack ajusters not work automatically. Maybe its time for a mechanic?