I bought the Microtuner a couple-a-three weeks ago. One of the things that I would like to tune up is the accuracy of the speedometer. It reads about 1.5 miles per hour faster than I am actually going. When I gather the information, I do it on long straight flat highways with cruise control preset as close I can visually set it nitpicking it until it is as perfect as I can get it.

Then I have compared three things:

1. The speedometer - I have timed it at 60 miles per hour against the mileage calibration posts available on the highways around here. They are one mile increments for 5 miles total. I have done this on four different 5 mile tests between Seattle and Portland, Oregon.

2. I have put my digital readout on the Odometer display into test mode and it reads 1.5 miles per hour slower than my speedometer needle says as well . And it seems to be "right on" comparing against the mileage calibration runs.

3. I know you aren't fond of GPSs for a point of reference, but given at least 5 or 6 good satelite signals and using the readings after giving the GPS time to settle (it does have to crunch some numbers from a consistent speed to arrive at a reliable steady value) it too seems to be right on per the mileage calibration runs and it matches the Odometer in test mode. It is spec'd at .1 MPH for accuracy and seems to be.

So, assuming that I am actually going 1.5 miles per hour slower than indicated I am going to use the Microtuner to set the tire diameter smaller in 1/4" increments to optimize the readings.

Will that change both the odometer test mode readout and the Needle reading?

Thanks,

Tom

 

Hi Tom,

This is far too detailed to get into here.

Very briefly.........

In short, forget about trying to make the speedometer as accurate as the odometer, it's virtually never going to be. There are different standards for odometers versus speedometers as I understand it.

You might want to try calling the manufacturer at the number listed in your documentation.

 

since I don't use the odometer as a speedometer indicator anyway. It was just used as a point of reference.

I was only asking if both get adjusted when I adjust for the tire hieght. I assume there will alway be a disparity between the two.

I will know soon enough I guess.

Thanks,

Tom Hall