I was lucky, the day I finished installing my rear disc's it started to drissle real heavy making the street slick. I set the valve so it didn't limit the rear brakes then putted up the street at 10 mph and put on the brakes. The rears locked up before the fronts even felt like they were working. Made an adjustment to the full limit and tested again. This time the fronts locked at 10 mph on the slick road but the rear didn't. I put the car away and waited for a dry day and found a safe section of roadway where I tested at slow speeds and worked up to faster speeds.
I can't stress enough, be careful and be safe when testing your cars brakes!