Look at it another way...if you were really speeding, like over 100mph the judge is not going to care one way or the other that your speedo was off. Any moron would know at that speed that he was speeding.

And if you were only speeding a little, like 15mph over a ticket lawyer will be able to help you out.

Grinding down the gear, if there even is such a thing sounds like alot of work for little benifit at high risk.