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Discussion Starter · #1 ·
Happy 2012 everybody, hope you're all doing well

Just put a readylift leveling kit on my '09 Laramie and added some 285/65R20 BFG AT's to the stock wheels (merry Xmass to me, by the way). Pictures to follow soon!

Now, of course, due to the change in tire circumference things like the odometer and speedometer are incorrect. Is there a cheap & easy way to fix this?

I normally wouldn't care, but my state (NC) requires an annual safety and emissions inspection, and I'm afraid it might include a check for accurate gages. I don't want to find out at the local inspection station that it must be fixed before I can renew my registration, and that he would be happy to fix it for me for a ridiculous price!

Thanks!
John
 

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Discussion Starter · #2 ·
So I found this website with a hand speedometer adjustment calculator...

http://www.csgnetwork.com/speedocalibcalc.html

Looks like for my change in tire size, I'm going 1 moh faster for every 20 mph. So if my gauge says I'm doing 60, I'm really doing about 63. No biggie, and I'm. Betting NC won't care either

John
 

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You can pick up a handheld programer like a diablo or a superchip, they have the ability to adjust for different tire seizes. Any dealership or speed shop can also flash the computer with the new tire spec easily enough. The programmers are better options because you can also have all the features, like octane tunes, code reader/clearing, etc.
 

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The 4th gen trucks only have the peramiters to change the tires sizes between the two stock heights. You will need a programer that has that function. Aslo remeber , if your speedo is off , then your heads up MPG reading will be off also.
 

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I have a bully dog in my 09, it can recal your spreedo but it was a pain, it gives you the tire size your running, and even tho you choose the correct one it wont be right, you have to keep playing with it to dial it in. I gave up lol
 

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I have a bully dog in my 09, it can recal your spreedo but it was a pain, it gives you the tire size your running, and even tho you choose the correct one it wont be right, you have to keep playing with it to dial it in. I gave up lol
I had the same problem with my DS. I just set it to what tire size I have (35") then hit the highway and checked the accuracy with GPS on my phone. It was off so I changed it until my speedo reflected the same MPH as my GPS. I ended up settling on 33.5" tall tires on my tuner.
 

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Programmes don't take into consideration height lost due to air pressure and load, they will give you true height readings. True height is usually about an inch (give or take a little) shorter then tire size indicates once you put the weight of the truck on it.
 

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I called and talked to the dealer today, and he told me that they can adjust your speedometer up to 285 tires. Said all they would have to do is hook it up and it would recalibrate it.
 
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