Speedo reads 2 off?

[Aerohead]

After 13 months, I finally received my Maverick Lariat 2.0 EB and so far I’m loving this truck. One of the things I noticed was when I’m going 35 on the speedometer my actual speed is 33 mph per GPS app, and it just feels wrong. Has anybody else encountered this problem with their miles being off? I’m running the Perelli‘s and you would’ve thought Ford would’ve adjusted for these.

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[NoVaJimmy]

Pretty much every vehicle I've ever owned had a speedo that indicated low. My Maverick is running 30" 235/60R18 tires and it's still about 1mph low compared to what Waze shows.

 

[Johnkn]

After 13 months, I finally received my Maverick Lariat 2.0 EB and so far I’m loving this truck. One of the things I noticed was when I’m going 35 on the speedometer my actual speed is 33 mph per GPS app, and it just feels wrong. Has anybody else encountered this problem with their miles being off? I’m running the Perelli‘s and you would’ve thought Ford would’ve adjusted for these.

So you can ‘feel’ a 6% difference at 33 mph? LOL

Add ~2psi to the tires and recheck with another GPS app.

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[Raymundo76]

After 13 months, I finally received my Maverick Lariat 2.0 EB and so far I’m loving this truck. One of the things I noticed was when I’m going 35 on the speedometer my actual speed is 33 mph per GPS app, and it just feels wrong. Has anybody else encountered this problem with their miles being off? I’m running the Perelli‘s and you would’ve thought Ford would’ve adjusted for these.

I've been using a Garmin GPS for more years than I can remember; It always is 1 or 2 MPH different than what the car shows. I do not know why. Might just be with the +/- accuracy of each system; so an agreement is not likely.

 

[kkreit01]

Mine is about 1 mph slow compared to my radar detector.

 

[Aerohead]

So you can ‘feel’ a 6% difference at 33 mph? LOL

Add ~2psi to the tires and recheck with another GPS app.

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Sonny, if you been driving for as many decades as I have, then yes, I can feel the difference.

 

[Baloo]

I never paid attention until after I changed tire size. To 245/65/17 and is it dead on.

 

[Old Man]

Per NOAA:
How accurate is GPS for speed measurement?
As with positioning, the speed accuracy of GPS depends on many factors.

The government provides the GPS signal in space with a global average user range rate error (URRE) of ≤0.006 m/sec over any 3-second interval, with 95% probability.

This measure must be combined with other factors outside the government's control, including satellite geometry, signal blockage, atmospheric conditions, and receiver design features/quality, to calculate a particular receiver's speed accuracy.

Speedometers have only 1-2 mph accuracy as are most radar units.

 

[Johnkn]

Sonny, if you been driving for as many decades as I have, then yes, I can feel the difference.

LOL, 6% at 33 MPH is a rounding error even within the different tire brands OEMs use let alone the marginal OEM size differences (225/235, 17/18") on the Maverick. And knowing as much as you claim, you should know that the speedometer is not necessarily linear, and if it's 2 MPH off at 33 it can also then be dead on at 55.... If it bothers you put a couple lbs of air in your tires.

PS, I've been driving for 5+ decades, I purchased my first BOSS-351 car in 1972 when I was 17.....


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[Johnkn]

Per NOAA:
How accurate is GPS for speed measurement?
As with positioning, the speed accuracy of GPS depends on many factors.

The government provides the GPS signal in space with a global average user range rate error (URRE) of ≤0.006 m/sec over any 3-second interval, with 95% probability.

This measure must be combined with other factors outside the government's control, including satellite geometry, signal blockage, atmospheric conditions, and receiver design features/quality, to calculate a particular receiver's speed accuracy.

Speedometers have only 1-2 mph accuracy as are most radar units.

LOL,. don't confuse the topic with facts....


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[Lynyrd Skynyrd]

Speedometers have only 1-2 mph accuracy as are most radar units.

Not all true. Most radar and speedometer are or can be spot on.
Let’s start with tires. Ford and Toyota with many* not all there vehicles undersize tires intentionally to skew the cafe numbers and make everyone think they get better mileage. On my F150 tires I called the tire manufacturer asking why they were smaller diameter. They said they are oem spec.
they can make any tire with 225/ 235/ 245 or any size as big or small as the oem pays to have made(mine were the stock General tires came on the Tremor)
We can increase tire size or use Forscan or a cool dealer service department to calibrate the speedometer and it will be accurate.
You can take a tire size and check exact spec across multiple tire manufacturers and the variance can be as much as 1/2” diameter. Do not take tire rack as gospel, I’ve went to each oem and followed up with tech support to learn tire rack numbers are not fully accurate . Again correctable.
Next is radar and GPS. I’ve checked my speedometer with multiple gps phones apple android they are all the same and all are spot on with police radar and street or tollway radar signs.

 

[UberGadgetFreak]

I wanted to add this link from a thread on sister-site Bronco6g about recalibrating the speedometer:
How to: Recalibrate Speedometer with Forscan for 2021 Bronco | Bronco6G - 2021+ Ford Bronco & Bronco Raptor Forum, News, Blog & Owners Community

And a sister thread from the Ford Truck forums:
Correcting the display MPG for better accuracy - Ford Truck Enthusiasts Forums (ford-trucks.com)

Interesting stuff to read if you want to try and make the speedo as accurate as you can. It will never be 100% accurate of course, but you can tweak it to be a bit better. Treadwear, air/tire pressure, and even sensor/gear wear can impact the accuracy, but these tips can help a lot to get as close as you can.

 

[Old Man]

Based on my experience working radar speedometers can be different, cold versus hot tires, air pressure. Even our radar guns were +/- 1 to 2 mph accurate depending on which one we used.

 

[Aerohead]

I wanted to add this link from a thread on sister-site Bronco6g about recalibrating the speedometer:
How to: Recalibrate Speedometer with Forscan for 2021 Bronco | Bronco6G - 2021+ Ford Bronco & Bronco Raptor Forum, News, Blog & Owners Community

And a sister thread from the Ford Truck forums:
Correcting the display MPG for better accuracy - Ford Truck Enthusiasts Forums (ford-trucks.com)

Interesting stuff to read if you want to try and make the speedo as accurate as you can. It will never be 100% accurate of course, but you can tweak it to be a bit better. Treadwear, air/tire pressure, and even sensor/gear wear can impact the accuracy, but these tips can help a lot to get as close as you can.

Thank you for the links. It seems like most of the information in this thread was the reasoning why the Speedo is off, not the solution. It appears Forscan maybe the answer to my question for adjusting the accuracy.

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