Speedometer off by 5 mph

Hello everyone. Just made a trip to Saint Louis and Waze has the route right at 600 miles, during the trip I noticed the speed and milage wasn't right. Well it was about 120 ( showed around 720 miles when I arrived) miles off for the trip. So i believe the speedometer is off by approx 5-6 mph ( faster than actual speed). The only change I have is the MPT tuner and a 93 tune it it.

Any suggestions?

Thanks for your help,

Vic

Adjust your tire size. When they made the tune they may have used the wrong tire size.

sorry to sound stupid. Can i do that with the N Gauge or another way. Thanks again..

waze is not correct with its speed indicator. get a gps speedo ap form the app store and i am sure you will find the factory speedo is spot on.

Thanks but something is wrong. I reset the Trip 1 when I went up and then back and it registered over 700 miles for a 600 mile trip. I think the tire size thing could be the issue. Is the best way just to contact MPT again and see if they can correct it?

Vic

Take it to a local speedometer repair place (find the one the cops use) they can test the truck on a treadmill and verify mph discrepancies

Your tire size is definitely off. Yes you can change the tire size with the Ngauge.

Thanks I'll try to Ngauge first. I saw the video on the website.

Waze data from sync via CarPlay is wrong. Wrong on my 2017 Raptor and wife’s 2019 explorer. Installed the Phoenix system with full screen CarPlay and it is correct. The CarPlay api allows for the vehicle system to be the GPS and speed data source and Sync is just wrong.


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I had this problem on CarPlay apps too -- updating to a new version of Ford Sync fixed it.