Towards the end of last season the faceplate on my tach melted. I didn't think too much about it, figured I'd get around to replacing it someday. But this season I noticed that when I'm doing the speed limit (by my speedo) people seem to fly by me. I wonder if it's related to the tach issue, and I'm also wondering if anyone else has had this problem?

 

Try getting someone to serve as a pace car/bike. Have them cruise at an agreed on speed and see if you are reading correctly. That will let you know if there really is a problem.
Ern