Speedometer tampering

[Limdu79]

I am upset that I can't get my speedometer corrected to an accurate reading. It consistently reads over the actual speed I'm going. When I choose to do the posted speed limit, which I'm legally allowed to do, I now have a safety concern in that I am forced to guess my speed. The company can adjust the device to be accurate but chooses not too, inforceing some notion that doing so will make drivers drive at slower speeds. This is what I justify as tampering.

 

I want it fixed.

[ASD Dad]

All manufacturers do that.  ALL.  It is far worse on motorcycles, some of my old bikes were almost 10mph off at 70mph!  They do it on purpose and have for many years.  It should really only be off at most 5mph at highway speeds.  It is less the slower you go and higher the faster you go.

 

If you REALLY want it changed this is most likely your only option - http://www.hypertech-inc.com/SpeedometerCalibrator.aspx

 

People use that when they have a drastic change like putting 33" mud tires on their Jeep and Trucks.

 

No OEM manufacturer is going to calibrate it for you.

[Limdu79]

Just because they all do it doesn't mean its ok. The laws need to be changed to account for this.

The speedometer is a measuring device directly tied to my well being and safety. It must be accurate.

[andy_george]

Settle down. ASD Dad is exactly right. All speedos are off a certain percentage and read faster than actual road speed. The difference in the circumference of a new tire vs. a worn tire will make a pretty big difference in indicated speed. So unless you plan to get a new set of $800 rubber ever year, I’d spend my time worrying about more important things in life.

[Mark Rogers]

Consider what would happen if the speedometer was calibrated at the factory to be exactly right.  That would be fantastic until the tires wear down (and the speedometer reading is too low) or the tires are replaced (and the speedometer reading is too high).

 

It's also illegal in some countries to have a speedometer that indicates lower than true speed.  The EU law is at http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:1975:196:0001:0005:EN:PDF. (Not sure if the US has a corresponding law or not.)  So if you calibrate your speedometer for a particular tread thickness and tire temperature, you could be breaking the law when conditions change, even if you manage to avoid speeding.

Edited July 13, 2020 by Mark Rogers