Are Honda odometers and speedometers known to be inaccurate?

[John_DiFool]

@mhendo

There are places that have roadside speed signs that flash up your current speed in an attempt to get you to remain within the speed limit. There’s one in my neighborhood in San Diego, and we actually saw one on a freeway on our drive up to San Francisco.

If those things are accurate, then the speedo on our 1998 Civic read a few miles an hour fast. When the one in our neighborhood shows my speed as 27mph, the speedometer actually reads about 30. And when the one on the freeway showed 63mph, the speedo said about 68.

There is cosine error to be aware of, which to make a long story short means the radar device will read higher than you are actually going.

[Tuckerfan]

All speedos lie.

So we sought out the rule book to find out just how much accuracy is mandated. 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. And those percentages are not of actual speed but rather a percentage of the total speed range indicated on the dial. So the four-percent allowable range on an 85-mph speedometer is 3.4 mph, and the acceptable range on a 150-mph speedometer is 6.0 mph.

(emphasis in the original)

If you read the full article you’ll see that Asian car makers speedos are the least accurate, while American’s have the most accurate. This is deliberate on the part of the car makers. In the US, the allowable deviation is determined by manufacturers as part of a mutual agreement, in other parts of the world, its mandated by law.

[Waenara]

Just a WAG, but if car manufacturers know that it’s almost impossibly to perfectly calibrate a speedometer perfectly (and accuracy is further affected by tire pressure, etc…), maybe they purposefully leave it slightly high because that’s better than being low.

Thinking that you’re going 65 when you’re really going 60 isn’t that bad. But if you thought you were going 65 and you’re really going 70, wouldn’t lots of people sue the manufacturer because they’d be getting more speeding tickets and there’s more of a safety issue (and liability issue) there?

[Joey_P]

I think it was mentioned upthread but there was a class action lawsuit against Honda about this not to long ago. I have a 2006 Honda Civic. During my lease term I am allowed 60,000 miles. Due to the lawsuit they had to change it to 67,000 for exactly this reason (the odometer being wrong).

[KneadToKnow]

Given more data, I’m forced to step back from my “balderdash” comment and instead say it’s a crazy frakkin’ world.

[RTFirefly]

@mhendo

the speedo on our 1998 Civic

Must’ve been a real stretch to get the Civic into a Speedo.

[Myglaren]

It isn’t only the Oriental manufacturers.
I have a Citroën C5 and visit several forums dedicated to French cars.
It is commonly acknowledged there that all French speedo’s read approximately 10% high. Many of the members have corroborated this with GPS comparisons.