G DIESEL

driving to work today I realized I can check when I drive through the EZ Pass lane it shows your speed, so tonight on my way home I will see what the difference is. I think the officer had a high reading bc I don't see it being off 10mph.

I also was asking if the factory NAV system has a independent speed source (it's displayed while in NAV mode)

iphonedylan

If you have a smart phone there are free GPS speedo apps that will give you your speed. I would think if your speedo really is off that much your navi would show it because that should be using satellites. The app would give you an independent reference.

G DIESEL

according to the ez pass speed display I'm 3MPH over what is indicated. Strange that Garmin reads the same as my speedo though.

so either the officers gun was off, or he was exaggerating and then "cut me a break" by writing it for the actual speed...hmmm.

kingoneyl

I just installed 35" tires on my new JKUR this weekend. I noticed the speedo and the NAV were reporting the same speed. I wondered if the shop had updated the speedo with a ProCal or something?

I grabbed my Garmin for a test. Turns out the speedo and NAV must be linked because they were 5mph off. When Garmin GPS was running 70 mph, the speedo & NAV were showing 65 mph.

So guess I need to lighten up on the right pedal until I get it re-calibrated.

MacBeJeepin

I bought my Unlimited X with Sahara wheels/tires and was off 6.5-7mph at 65mph (but was actually going 72mph)

Just fixed it with ProCal

OutlawJK

Your nav gets its speed signal from the ECM thats why the speedometer and nav are the same #

you must use a stand alone gps for verification

G DIESEL

Hmmm it's all starting to make sense!

Moe.JKU

Are you talking about those signs that flash your speed when you go past those. Because around my area it actaully shows ur going a couple mph faster than you are. Just to slow you down a bit. And this info was giving to me by the cheif officer of the area who is a friend of the family. So i would think its correct information

MTG

X2 on the smart phone app.

To the OP: Why not just order up a AEV procal and use it to correct your speedo and shift points?

ZERO LIMITZ

With 35" my mph is 4 mph off...... I have a ticket to prove it.... I have the iPhone app now.... And it also shows 4mph over