Speedometer

[Nate03]

So since I have gotten the Expy I have felt like the speedo is slow because going the speed I used to go in my old car had people riding my tail and that has never happened. I used a GPS app to check the speed and it is off by 2 mph at nearly every speed. I checked the app against other vehicles and a roadside cop sign that shows your speed and it is dead on. Anyone else have this issue? Would that be a warranty fix? Also, wouldn't that increase my mileage? At 60 mph it is 2 mph and actually going 58. If that's the case my car is over 3% off on the mileage. At this point that could be 1,000 miles!! Any thoughts?

 

[Nate03]

It is a 2017 XLT by the way. It did come from Canada, so not sure if that is the problem.

 

[cmiles97]

I also have a 2017 XLT but an EL. My speedometer runs 1 mph slower than my Garmin GPS. My work van runs 3mph slow!

I've found many vehicles are off. Others spot on. Now what if my Garmin GPS is off?

Not related but good to vent:
The work van is also GPS tracked (Verizon) by the company. I kept getting dinged for speeding which I wasn't. I contacted Verizon's division that oversees this. They had to update the firmware on the unit in my vehicle, it was reading 6mph high.

 

[Nate03]

I think I would rather it be slow, because am I incorrect in assuming this is tacking on roughly 3.4% more miles than it should be? That means at 100k miles I will only have 96700. Also, my warranty will be over roughly 1k sooner than it should.

 

[cmiles97]

You may enjoy this article. I can attest my 16 SS Camaro and 07 Sequoia were both spot on.

https://www.caranddriver.com/features/speedometer-scandal

 

[chuck s]

... You linked to an an article from sixteen (16) years ago!

1.5% +/- variation is the allowed tolerance I see in Federal statutes as "reasonable". At 70mph that anywhere between 68.95 and 71.05 mph. I doubt you can interpret the needle that closely at any speed and the digital display on the two cars I have with it read to the nearest whole number.

Commercial GPS will sometimes show I'm driving in a corn field or the wrong way on a divided highway in some atmospheric conditions so 1.5% tolerance for speed may be all the better some GPS units can do as well.

Speedos depend on OEM tire sizes, of course. I think there's some correction that can be made in Forscan.

-- Chuck

 

[star-art]

A speedo readout can be off as much as +/- 4 MPH. If you have a digital readout, it might not match your analog gauge, either. A likely cause for a "slow" reading is your tires. If you put slightly larger tires on your factory wheels, it slows down the speedometer readout at highway speeds.