Right well as I am posting to try and fix the c/l issue thought I would confirm another

Noticed my sat nav GPS reading is 2mph out to speedo reading - now I kno this is usually the norm but not that the speedo is under reading - 70mph is actually 72 GPS

Now the tyres are all 205/55/16 tey are worn but never come across this in the past.

Anyone else noticed this? Will hook up the road angle tommorrow for a 2nd GPS reading

DG

Sounds normal to me speedo will have a +/- tolerance @ 70

Edited 24 October, 201114 yr by missingmyvrs

speedo will always under read never over.

I have more difference in my speedo the slower I go. The faster the I go the more accurate it becomes (GPS confirmed)

I have more difference in my speedo the slower I go. The faster the I go the more accurate it becomes (GPS confirmed)

That sounds suspect.

I've never known Any car get more accurate the faster it goes, even new cars are normally more than 9mph out when travelling 90mph+.

It's also worth noting that gps like sat Nav or road angle are by no means accurate either.

Right I will get eh race logic box on at the weekend to confirm but all cars will under read for the legal reasons but never seen one above with oe size wheel / tyres on

Will confirm

DG

Assuming a perfectly accurate speedometer, my trigonometry says that you could achieve this by driving up or down a slope of arctan(1/35) or about 1.6 degrees.

On a hill, a speedo measures sqrt (VX^2+VY^2+VZ^2), whereas a GPS outputs sqrt (VX^2+VY^2), where the XY plane is tangent to the spheroid at your location, and the Z axis is normal to the XY plane. See the difference?