If you cannot keep up with traffic, you are impeding drivers. If the speed limit is faster than 50MPH, this is likely the case. Doesn't matter if your speedometer is reading 63 or 66 MPH, you are still holding up traffic.1. If you believe the factory speedometer you will think you can ride on a 60 mph highway without impeding other drivers
You are still only changing one variable. The speedometer may not be accurate, but it is precise. You still get a relative measurement.2. You cannot intelligently make engine and sprocket changes to optimize performance for your specific riding needs or wants if your measurement instruments are lying to you.
This is the internet. If I was to believe everything I read, Queen Elizabeth is a cannibal, the earth is flat and I have $1B in some offshore account waiting for me to claim.3. This thread is all about "how fast have you had your Z125 going". If you answer that question by quoting your lying speedometer or tachometer, you are lying to everyone who wants to know the REAL answer to the question. If we are going to post lies, why bother to even ask the question?