On 13/02/2019 16:54, Dave Plowman (News) wrote:
As I said - a very optimistic speedo. Some makers today do just the same.
When making one which is within 1% accuracy should be child's play since
they are counting pulses.

They all do that. 8% high in my experience.

If you aren't careful you won't measure 0-60 times, you'll measure
acceleration to 60 - 8%.

And you'll work out your fuel consumption at a steady 50, not a steady 56...

Win-win for the manufacturer...

I tend to use the tacho. 20MPH per 1000RPM in top, bang on the button,
checked against GPS when straight, level and steady - and I've never
noticed any effect from tyre wear.

The speedo is just somewhere between the marks.

Andy