Speed Observations

[OctopusWrangler]

Don't know why this is coming back to me now...
A few weeks ago I drove up to Vegas and back, first time I had the opportunity and excuse to do so. From Phoenix it's about 4-4.5 hours depending on where in Phoenix you live.
For the trip I had an Escort 9500 going to keep me out of trouble, and one neat feature is that it can display your speeds.
I generally had cruise control set at 70 or 75 (minus a few stretches of some spirited driving). I noticed that the Escort was consistently 3 miles per hour faster that what I was showing, ie if I had cruise set at 75 the Escort showed 78.
Wondering if anyone else has noticed this, and which was correct or closer?
I can understand a slight difference, but 3 MPH is a little higher than i would have expected.

Sponsored

 

[FiveLiterDreamer]

I've noticed differences on the lower end with a GPS speedo but typically within one to two mph always lower. did you perhaps change wheels or tires on your car OP?

 

[10splaya22]

The car should show a couple mph higher than actual speed (1-3% usually) as mandated by law. But your situation is strange and you should double check it with your phone gps.

 

[r-model]

I noticed the same with my car, I am using a TomTom gps unit and it showed that I was actually going faster than what was indicated on my speedo.

 

[OctopusWrangler]

Thanks, at least I'm not the only one, so I know I'm not crazy.

 

[BrownDogg]

I am glad you posted this. My 2015 performance pack with the 19"s does the same thing and it has been driving me nuts. I was wondering if my speedo was off. Mine shows off by the same margin of about 3 mph.

I have a passport escort max 2 which I know is accurate. I also have a speedo app on my iPhone which is 100% independent of my radar and the speeds match on those.

I had in my old 2014 mustang and the speedo matched the radar detectors speed dead on. Within 1mph of it give or take and same situation in my previous car which was a 2006 Subaru wrx STI and speed matched there too.

I can only think the cars speedometer isn't properly calibrated for the wheels it comes with which is crazy.

 

[Zodiac]

I even notice on my GT when I set cruise control it will say for example set at 74, but if I look on the speedometer it's usually a tick or two above 75.

 

[fionic]

Don't know why this is coming back to me now...
A few weeks ago I drove up to Vegas and back, first time I had the opportunity and excuse to do so. From Phoenix it's about 4-4.5 hours depending on where in Phoenix you live.
For the trip I had an Escort 9500 going to keep me out of trouble, and one neat feature is that it can display your speeds.
I generally had cruise control set at 70 or 75 (minus a few stretches of some spirited driving). I noticed that the Escort was consistently 3 miles per hour faster that what I was showing, ie if I had cruise set at 75 the Escort showed 78.
Wondering if anyone else has noticed this, and which was correct or closer?
I can understand a slight difference, but 3 MPH is a little higher than i would have expected.

within margin of error for for laser/radar I think. I wouldn't worry about it.

 

[Asharus]

interesting. all my previous cars have had a faster speedo by about 3mph. normally they would read 80mph and your actual speed would be 77mph. i was told this was so your warranty runs out sooner.

ill check tomorrow on my waze whether or not our speedo is actually slower than our actual speed. i would think of this as a good thing.

 

[WeinerDog]

The car should show a couple mph higher than actual speed (1-3% usually) as mandated by law. But your situation is strange and you should double check it with your phone gps.

What law, specifically?

 

[Herr Squid]

My speedo seems to run about 2 MPH low according to GPS and those asinine "your speed is..." signs the city loves to harass us with.

 

[GT Pony]

I checked my speedo against a Garmin GPS that read to 1/10 MPH. Had a helper record the GPS speed reading when I told her when I was steady on the mark with the speedo.

Results:
Speedo @ 50 MPH - GPS @ 49.4 MPH
Speedo @ 70 MPH - GPS @ 69.8 MPH
Speedo @ 100 MPH - GPS @ 100.0 MPH

I'd say it's pretty accurate on my car. Also, if I set the cruise control to 70, the speedo is within half a needle width of 70.

Update - to add, I did make sure I was looking directly straight into the speedo to take out any parallax which could throw off the readings.

 

[Tazdevil 66]

i have not compared to a GPS or any other device....the speedometer is not directly in front of our eyes (to the right) and we are looking at it from an angle.....shift your head to the right and look at it head on.....you might see a small difference in wat speed you are traveling, I do. So now as opposed to thinking I am 2-3 mph off I am 0-1 mph off (speedo reading faster)

 

[Asharus]

i tested it today as well. it's spot on when going 90mph, but it seems like it reads a couple mph lower at much lower speeds, like 35mph on the speedo reads 38mph on waze.

 

[GT Pony]

Also make sure your tires are inflated to the correct pressure when cold before conducting any tests. The speedo will read high if the tires are lower than they should be.

Sponsored