[hawk2100n]

Originally Posted by California98Civic

These are really interesting results. And thanks very much for them. I really appreciate the commentary on the way the GPS works. And I'd also love to have more d-series Civics test this stuff. Your last comments also raise some things I'm still curious about. (1) Do we know what the stock tire was and what its rated revs/mile was? I at least don't, and if I read the tirerack.com listings I see significantly varying revs/mile ratings for different tires in the same size category. And (2) in my experience the speedometer error tends to be higher than actual while the ODO is lower than actual. You cannot get the ODO and the speedometer to both read accurately at the same time. At least I can't. That suggests Honda designed the system to report "erroneously" for some reason, no?

Vexing.

I'll see if I can do some digging to come up with data on the stock tires. One thing I know is that the 1996 DX came with 13" steelies while the 97+ were all on 14" wheels. I'll look into some parts references to see if there is any difference between VSS data for these years.

For your 2nd question, it reminds me of a good article from Car and Driver on odometers and speedometers. Pulled this one from way out of the mental archives, 2002...

Speedometer Scandal! - Feature - Car and Driver

In the U.S., manufacturers voluntarily follow the standard set by the Society of Automotive Engineers, J1226, which is pretty lax. To begin with, manufacturers are afforded the latitude to aim for within plus-or-minus two percent of absolute accuracy or to introduce bias to read high on a sliding scale of from minus-one to plus-three percent at low speeds to zero to plus-four percent above 55 mph... ...odometer accuracy is more tightly controlled to plus-or-minus four percent of actual mileage.

It goes on to give details where the error can be even worse in many situations. All supporting that the error we are seeing is real.

One thing I know is that high speedometers help reduce speeding tickets on a macro scale. Make people think they are going faster than they are and all of sudden they are now only going 63 instead of 65 in that 55 zone and the cop lets them go.