engine rpm at 100kmh

[Al Campbell]

270 degree meter movements are often non-linear. I'm not suggesting these ones are, but it wont help.

Also tyres don't  necessarily match the size the formula suggests. I measured the circumference of a brand new tyre at 38psi by rolling it along the flat driveway for as many revolutions as I could measure with a 100m tape measure. Came out 3% smaller. Not a lot I know, but are others worse? And that was before any tread wear. I used that measurement to programme a bicycle computer to re-calibrate the speedo after replacing the needle. Don't laugh, when I finally got hold of a GPS I couldn't tell the difference between the two.

For the record, my speedo reads 15km/h low at 100km/h. Managed to get it accurate from 40 to 60km/h.

AL.

[martym00se72]

Had some smooth freeway running over Sunday - 3300rpm in 5th @110kph (verified by GPS in my phone). Speedo out (slow) by approx 15kph    So it makes me wonder what I was actually doing when I blasted past a truck a few weeks ago and just kept it nailed...  lucky mister plod wasn't around then