Home › Forums › Stay Dirty Lounge › The EricTheCarGuy Video Forum › How To Replace Rear Disc Brakes (Full) › Re: How To Replace Rear Disc Brakes (Full) November 6, 2012 at 2:17 am #474377 EricTheCarGuyKeymaster It’s an impact driver, that’s how the tool is used. [quote=”TechGuy8″ post=36578]What is the purpose of hitting the philips screw driver with a hammer (@2:51) after installing the new rotor?[/quote]