Hey fisherman, which direction is yours off? Is the speedo too fast or too slow?

I would expect the behavior like voodoo described but its the opposite. I actually need larger tires in order to get the speedo to match my real speed.

 

I hope Jamie. He seems to be the one wearing the pants.

 

Looking around other automotive forums, the general concensus seems to be that car manufacturers design their speedos to be slightly lower than you are actually travelling. Reasons given for this vary, but most feel it is a liability prevention issue, ie it should never be proven you were going too fast because your speedo was under reporting the correct speed, so they build in a little "buffer". Naturally there will be some variation when people change tire size, so it IS possible the GPS is right, and the speedo is wrong after all. This will be interesting to see the results. If I have time, I may test this myself.

 

i have the pioneer avic-z1, its an indash nav system and the speedo on it is almost exact. The VSS wire is not connected so it is not getting the info from the vehicle itself. Donno if this is relevant to the origional question or not.

 

which package do you have marin? base? adventure? luxury?