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Discussion Starter #1 (Edited)
With the new 33" tires and no new diff gears to compensate, our Jeep now has a 12% speedo error, reading lower than actual. I poked around in the iTunes store and found something called Speedometer+. It was free, so I went for it. I think I lucked into an introductory offer and they raised the price on January 1 to 99 cents, or something. One of my co-workers found it in the Android market for that price, too.

Although the dial display is hard to read, there's a decent size digital readout, too. This will work just fine until I get the gears changed. I may still need it then if I go sick with the gearing, but then our Jeep's speedo is liable to read too high instead of too low.

Here's what it looks like propped up on the dash.

Old news? New news? News to me, anyway.

Dan
 

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Get the AEV procal for 99 bucks and you can correct it now AND again after the regear. Among other things.
 

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i downloaded the app.... it is $.99 so why not.... i have a free one that was completely digital but lets see how this works!

I have the AEV procal but it is fun to see if it is true!
 

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Discussion Starter #4
Thanks. I'll look into it. Does that correct at the ECU level so the odometer gets corrected, too?
 

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If you are running an auto it is especially important that you reprogram the PCM to correct the speedo as this affects your transmission shift points as well. There are a number of programming options. some dealers my be able to reprogram tire size for you.
 

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Thanks. I'll look into it. Does that correct at the ECU level so the odometer gets corrected, too?
yeah the aev is the simplest solution to regearing and over sized tires!!! definitely get it!
 

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I'd have to say aeroforce gauge.... If ya wanna spend some cash. But totally worth it, and you can change your tire size and much much more.
 

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Discussion Starter #10
I was able to get the speedo re-calibrated at the dealer. Pretty simple. All they needed to know was the rev/mile rating of the new tires (630, in my case).

I'll buy a Procal soon enough, though, because I'll be changing gears down the road and I do want to be able to tweak the TPMS trigger threshold to match these tires. Their load rating is so much higher than stock that they can support a lower static pressure on the highway. All I need to do now is calculate what that should be.

I don't need much of the other Procal capability, though. The 2012 JK has the one-touch three-blink turn signals already (which I like), and I already have a device to read and reset trouble codes.

Dan
 

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With my 33's the speedo actually reads dead on without recal. I have the suspicion that the manufacturer calibrates the speedos on new vehicles so that the warranty mileage is reached sooner. I have tested this out on several vehicles with no modifications and the GPS speed always reads slower than the vehicles speedometer shows. Even the digital radars that local police forces put up on the sides of roads has proved this to me.
 

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Also motionX lite is a free app that is handy for way more than speed. It's also a track recorder, so you can map trails
 
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