Originally posted by Tony Davis
They're are probably the most accurate speedo you can buy, and if it says your going 87mph, you almost certainly are!!!!!
They are filled with glycerin to stop the needle bouncing around!
We had both Gaffrig and Nordskog speedos on the Reefer. Both pitot tube types - the difference being the Gaffig was liquid filled and the Nordskog wasn't.
The Nordskog needle was all over the place, the Gaffrig extremely steady and accurate. It was always within 1-2 mph of GPS speed.