Put a 55 on and still had a speedo reading of 1mph to 2mph higher then the GPS showed. For me that is close enough, as long as I can figure out what the true mph are I can use that info to help answer that age old question, " Do you know how fast you were going?".
By the way, "Faster and faster until the thrill of speed overcomes the fear of death?" is not a good reply to the above question. A friend tried it thinking humor would easy the situation, not so much...