Speedometer Accuracy

[jtharris]

The speedo on My 2010, 3.8, sedan, 17" wheels, reads about 5% low. So, at 5 MPH true speed, the reading is 62 MPH. (True speed determined with several GPS' and a measured mile.)

Can the speedometer be calibrated to correct the error?

 

[ctrcbob]

The speedo on My 2010, 3.8, sedan, 17" wheels, reads about 5% low. So, at 5 MPH true speed, the reading is 62 MPH. (True speed determined with several GPS' and a measured mile.)

Can the speedometer be calibrated to correct the error?

I "assume" you mean at 65 mph true speed.

No, you can't recalibrate it. The best you can do is to buy the next size oversize tires.

All cars have this "problem" but it does help to keep you from getting speeding tickets.

All my cars in the past, that I've been able to compare to GPS's, all read higher than true speed. Not something to worry about.

 

[cschuler]

Mine reads about 3 mph higher than actual road speed at 70.

 

[scotttisha]

with my aftermarket wheel and tire set up, my speedo says 70 and my GPS say 68-69.

Scott

 

[mikec]

Auto speedometers are always set to read just a bit high... primarily because the law says they can't read lower than actual speed: can't use "but my car said I was only doing 65MPH" in court.

If you consider pretty much any electrical or mechanical system has some tolerance on accuracy - lets say +/- 2MPH for a speedometer - then the manufacturer will design the speedometer to read 67MPH when you're actually going 65MPH. Then the cars coming off the production line should read anywhere from 65 to 69MPH... with the "bell curve" centered at 67MPH in theory. Tire inflation and tire wear make a difference too.

Having said all that, I've found most car speedometers to read about 1MPH fast. Same for my Genesis based on the nav GPS readout. There is another thread on Genesis speedometer errors; several folks reported their speedometer reads several MPH too fast. Big errors - worst I've ever seen.

mike c.

 

[BocaDave]

Re: Speedometer Accuracy - TRIP COMPUTER EFFECT

So.... If your speedometer is off by say 5%, (either high or low), is your trip computer still correct in its displays of MPG and miles traveled?