Anyone notice their speedometer is off?

Speedometer Error about 1 MPH?--Some evidence | PriusChat and a few posts after mine.

 

Speedometer reads 48 mph at 50 mph on my PIPa.

 

Yes it's off on all Prius. One solution is go with 205 tires when you re-tire. It corrects the speedometer and the slightly larger tires look better. Lots of threads on the topic with details on effects on mpg and odometer readings.

 

so, if i'm traveling 55 (according to the speedo) in the right lane, whe i look in the rearview mirror, that's why the guy behind me looks like he's swearing?

 

Yep, when someone is riding my bumper, I make sure to do 2MPH more than what the speedo says, just to avoid road rage situations. It sucks that Toyota did this, but it's one of those annoyances we have to live with.

 

I often do the same.

 

Not just the Prius, my VWs did the same thing. I add 1mph to what my GPS says I'm doing.

 

Prius is off by 2mph (at least mine is). Makes you wonder how many road rage incidents were caused (and gas wasted by people angrily passing Prius vehicles) by Toyota just to save gas by fooling us via the speedometer

 

Lets not forget the MPG computer that seems to almost always be 2-4 mpg optimistic....

 

when compared to my plug-in garmin gps my speedometer is spot on

 

Since most car speedometers read high, I can only conclude that a lot of people driving Prii and being surprised at the speedometer optimism either have their first car or never paid attention to their speedometer accuracy before.

 

Part of the reason may also be the digital aspect. 2 mph is difficult to discern with analog gauges.

 

good point.

 

On my 2004 it varies. At street speeds it reads 1 mph high and 2 mph high at highway speeds.

Interestingly, there is a button dance on the early 2nd generation to get to a maintenance screen where you can see internal GPS data with the same speed difference.

iPad ? HD

 

It's not just Toyota. Many manufacturers add this inaccuracy to their speedos.

 

The speedometers reading high and the disabled screen functionality while the car is moving are both likely the result of demands from the rather conservative Toyota lawyers, rather than any technical reason. Apparently some car manufacturer(s) got sued by customers who got speeding tickets because they relied on a speedometer that read low.

 

Since my ICE doesn't pop on until I hit 65mph, that's a clue…

 

I obey the speedometer since that's the only legal measurement of speed. However, I try to keep the speedometer exactly at the PSL rather than driving with a lower reported speed to avoid "speeding", which is strictly what you should do.

If someone's riding my bumper I follow the Maine Driver's Handbook:

 

wow, 'drive slower' and 'reduce speed slowly', unheard of! those crazy maniacs.