Speedometer off....anyone else?

[RedRider]

All vehicles from all manufacturers have been off by about 3% since the fifties. Its intentional to to account for the worst possible variation in tire size. You can change the revolution count per mile in the computer (I've done mine) if you know how to alter the settings.

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[Azmig88]

It sounds like some of you think this is a laughing matter.?.? It is NOT!
How this issue should be addressed, MUST BE decided by The Supreme Court of The United States of America.
Because of the potential for damages and pain and suffering, I’d highly recommend the most expensive team of attorneys and engineers money can buy. This is a most serious dilemma.
Don’t hesitate to get started. Do it NOW!

 

[BluegrassNbass]

My 2013 silveraydo is tits on the gps and the ol speedo stick.

 

[BluegrassNbass]

No kids on this click

 

[MiMav]

I work for a tier 1 supplier that makes instrument clusters (and other components) for multiple OEMs. The clusters are specified to favor reading high. A common tolerance would be something like 60 +3/-0 MPH, so they tend to be in the middle of that tolerance. Even digital clusters will bump up the speed data they receive on the CAN bus.

By the way, temperature gauges tend to be the worst for displaying true data. A wide range of temperature will not move the gauge when it's in a "normal" range. It keeps the pesky customer from thinking something may be wrong.

 

[Azmig88]

No kids on this click

I’m thinking he prefers Chevys

 

[2lbgill]

Off 1 mph at what speed, 100 mph? 10 mph?

Adjust the tire pressure by 2 psi. LOL. The minute tire OD difference will compensate for the negligible speedometer difference, Or drive in temps that are 10* different than you current test as temp effects pressure (which effects diameter).


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Good answer and the correct one

 

[Matso]

Ford's having a rough season, I'll take the under.

 

[rivermaverick]

By the way, temperature gauges tend to be the worst for displaying true data. A wide range of temperature will not move the gauge when it's in a "normal" range. It keeps the pesky customer from thinking something may be wrong.

Agreed , temp gauges will show the warm up then stay in the center to keep people happy.
Back in the day temperature gauges had real numbers on them but people would panic if the temp went over 212 degrees not realizing that is not boiling in a pressurized system. Manufacturers responded by changing the gages to show Low/Normal/Hot but people did not understand that anywhere in the Normal range was 'normal'.
I did a test on a 'high end' vehicle a few years ago - the temp gauge stayed in the center until the temp reached 112 degree C then went to the high end of 'Normal', at 119 degrees it went into the red and the overheat light came on! (Boiling point in a 15 PSI cooling system is about 130 degrees C).
My Mazda has a light, Blue for cold and Red for hot - just as effective.

 

[rivermaverick]

So.... About GPS first: it's always off by 1-3 miles due to triangulation(known fact). 2) digital street sight is always incorrect.... It cost money to correctly set it up and monthly maintenance( ask a police officer who stoped you when it was last time serviced and you might get out of ticket if it's above 30 days).
3) vehicle speedometer vs digital is off by 1-2 miles.... In Nova days I will trust digital more. Than blank needle spot.

I've noticed that the analog speedo shows a little bit higher than the digital one over 60 MPH maybe 1 MPH but the speedo does not have 1 MPH markings.
I was a bit surprised the the Mav has a 'real' needle for the speedo, so the discrepancy may be just a parallax error!

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