Speedometer accuracy?

[46hemi]

Does anyone know how accurate our speedo's are? Are GPS's a good way to know for sure? I am particularly interested in the accuracy once over 100MPH and if it gets progressively less correct as your speed increases.

 

[BadVenm]

I've always understood the faster you are going the less accurate your speedo will be, if it's off to begin with.

I take a hand-held GPS with me if I want to make a run and check the speedo. I've used it on motorcycles, boats, and cars. It is a great little device. Check one out!

Also, if you are like my nephew who has a best friend who is a cop.........You know the rest!

Let us know if you make a top speed run (in a closed course - safe enviroment ONLY) and the out come of the GPS, or Radar VS. the Speedo.

 

[Paul Hawker]

From my own experience, and those of my fellow Silver State racers, the accuracy of the Viper speedo is very precise, even at speeds +/- 160 mph. We checked against mile markers, and GPS.
Much better than most hi performance cars who tend to exaggerate the car's speed.
If you have changed tires, wheels or axle ratio's then it is a whole different ball game.
GPS is challenged for accuracy unless you are on a very straight road.

 

[HSSSTOY]

..On an oval test track in Quebec Canada, one magazine reported a 99 GTS was clocked by a radar at 300 Km/Hr. while the speedometer read 315 Km/Hr., according to the test driver in 1999....I still recall this because I bought my GTS that year.

 

[Greg 99ACR Red and Silver]

To back up Paul's comment, I crossed the Silverstate Finish line at 165mph indicated, measured the same number on my GPS and the Event's radar measured trap speed was exactly 165. Precise is the word!

 

[WESTCOAST JASON]

At this latest Silver State I was disqualified for exceeding tech speed. We had just put 19" purners on the car for the event and I went right at 165 a few times during the race. (indicated 165 that is) Anyhow - in the results section you will see disqualified for high speed. (My navigator was 'stopwatch' challenged and was not able to aid me)

When we got back a GPS test was run and I found out that 165 is 188mph with Purner 19"'s on a 3.07 based 96 GTS. Honest mistake, all the preparation for the silver state and down the tubes for not checking tire diameter. Oh well, it was fun. (also explains why we passed 3 cars during the race. I have run the SSCC 5 times and never passed more than 1 car during the race)

 

[ViperGTS]

5% (sometimes more)