Speedometer is six mph too fast

An exact 6 miles difference indicates the new meter is the same but the needle has been dislodged out of position or calibrated wrongly during assembly.

Shop manual instruction is to replace the meter if out of specs, meaning it is non serviceable.

The dial tends to break if you try to pull it out and even if you are able to pull it out, recalibrating it to show correctly is not going to be easy as you have no way of determining the initial position of the pin when the dial is out.

Hello, just wanted you to know that I was able to get the dial to read fairly close to accurate (i.e. 1 to 3 miles faster than what my GPS unit reads) by taking off the plastic transparent shield in front of the speedometer then carefully removing the speedometer dial from its drive shaft. By lengthy trial and error (removing and reseating the dial onto its shaft) I was able to reduce the speed discrepancy from six miles to two-to-three miles per hour too fast. I was reading that the manufacturer habitually leaves the adjustment slightly too fast to prevent us drivers from claiming they caused us to get a speeding ticket. Then, on a hunch, I used my GPS unit to test my old 1984 Toyota Corolla that I have been driving for over fifteen years, and lo and behold, apparently all those years I had been using a speedometer that was four miles per hour too fast and just got used to the discrepancy over time. I have decided to leave the speedometer in the 1993 Corolla at the two-to-three miles per hour too fast setting since it appears I have living with the discrepancy for years already in my older car. However, do you recommend I get the 1993 car onto a dyno machine and then try to set the speedometer to a "dead on" reading? In your professional opinion, is it worth the trouble to make sure that the speedometer is fully accurate or as much so as possible? Could it be true that many speedometers are actually intentionally set to read slightly "optimistic" for the abovementioned reason? Thanks for any feedback you can offer.

Is it really that important to have the correct speed? If yes, forget the speedometer, use the GPS.

Personally I do not see the need to be dead on because when tire threads wear, the circumference would be reduces and that would chenge the speed so some difference is expected. No speedometer would be dead on forever.

Road and wind condition would change the aerodynamics of the vehicle and cause fluctuations in vehicle speed so it is never easy to maintain a steady speed.

Thank you very much for your latest reply stating that a speedometer cannot be expected to "be dead on forever". I had not even considered the prospect that external factors such as tire wear and road and wind conditions could affect the overall accuracy of the speedometer reading. I will not hesitate to continue to use your website as a valuable resource for automotive education as well as for advice on specific fixes. Thank you again.

You're welcome.

Have a nice day.