Speedometer wrong.

[leatherneck]

First, thanks for having me. I'm a noob so If I failed to find this elsewhere in the forum I apologize

First jeep. 2012 Rubicon. Just bought it 2 weeks ago. 39k miles. Manual trans. Tires/wheels are stock.

I noticed I seemed to be going slower than the traffic around me so I installed a GPS test app on my phone and at around the 60-70mph range the speedometer is reading about 5mph faster than the GPS says I am moving. I would expect a discrepancy with over/undersized tires but according to the door pillar label I am right where I should be with the tire size.

Any ideas?

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[mark sr]

I wonder if the previous owner had bigger tires on it, had the speedo adjusted and then put the stock tires/rims back on prior to selling it ??

 

[k-2]

Marks answer is most likely - with a scanner check the calibration (tire size)?

 

[JPNinPA]

Use mile markers on the side of the highway. Drive at least 10 miles and see if the odometer is correct. This is the most accurate I've found. I was driving 500 miles for a short time and found I was only off 1/10 in 500.
It's all calculated from the number of revolutions.
As mentioned they may have recalled from using larger tires and never corrected. Also check the tag on the rear to see that the gearing hasn't changed as well.


JPNinPA
Using Jeepz.com app

 

[TerryMason]

I have a Bluetooth ODBII scanner that I got off ebay for $20. I plug the ODBII scanner into my Jeep's computer and this allows the phone to talk to the Jeep. I then use the "torque" app on my android phone, and can see my GPS speed versus what my Jeep thinks it's doing. I've gotten more use out of this scanner that I would have ever expected.

I fixed my inaccurate speedometer by buying something called a speedohealer
https://www.jeepz.com/forum/product-reviews/41785-speedohealer-correcting-your-speedometer.html

 

[JPNinPA]

My method is low tec and free.

Regards,
JPNinPA

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[TerryMason]

My method is low tec and free.

Yeah, but who cares about price when you could have another screen to stare at while driving down the street!

 

[leatherneck]

Yeah, I hate how driving distracts me from my music selections, phone calls, and texts.

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[superj]

I have the torque app and a plug in obd deal also. man, that is a great set up. not only does it tell you what every sensor is reading, you can also scan for error codes and reset lights once you fix stuff. I have used that on a number of vehicles with my son's Toyota camry being the one its used on right now