Gig is right on. I had a 2004 F150 that traveled 5 at 40mph, at 60 it was more, over what the speedometer reading was. I was going 45 in a 40 with the cruise on and couldn't understand why an officer pulled me over and gave me a ticket for 50 in a 40. Of course, I blamed the officers radar equipment for needing to be re-calibrated, that was not the case. I had an officer that lived across the street for me so I asked him to come up to the main road, I set the cruise on 40 and drove past him. When I turned around and came back he said I had you at a steady 45, even showed me his reading. If two different radars were consistent that told me I was the one with faulty equipment. So, moral of the story, speedometers aren't always correct.gigag04 wrote:Light in the mirror is so he can see you hiding drugs and grabbing a weapon.Hoi Polloi wrote:I had the same thing happen to me driving through south Texas. I had the cruise control on, was going from one freeway to another, an officer pulled me over shining his flood light into my rearview mirror on purpose while I was driving slowly with my flashers on waiting to get off a bridge to pull over, and then he said I was doing something like 12 over, but he'd be nice and only give me 9 over when my cruise was set to 4 over, which was 1 under from the previous highway. Ridiculous.
Just because your un-certified speedometer reads a certain speed does not mean that is the actual speed of the vehicle.
We have done some tests at work with our personal vehicles and factory speedos are not always correct. Usually they read over what you are really going. Sometimes they get it backwards and you get paper.
Now, I check all my cars with my GPS. The truck I own now, 2006 Nissan Frontier, is 1 mph under what the speedo says.