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Discussion Starter #1
So, I got my new 285/65/20 tires on the stock rim or my 2011 Denali. No issue with that part.

I bought a tire calibrator (rough country) and it is worse then just leaving it stock in regards to the speedometer. I can tell (or feel like I can) difference on the shift points and overall better feel of the truck vs the stock tune.

I am very curious to know if this is just me thinking there is a difference, OR does this tire calibrator do more than just TRY to correct the speedometer because it fails unbelievably not doing anything with the speedometer.

Anyone know of a better speedometer calibrator or do I just leave it as is with the stock tune?

Currently it is the Rough Country Speedometer Calibrator # 90009.
 

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When I went to the 19.5s I bought a Hypertech programmer that worked great.
 

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2006 LBZ CCSB Leveled, Hypertech Programmer, 2008 LMM WT, 2008 Gasser WT
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207 Posts
I've used Hypertech speedo calibrators on 3 trucks without issue.
 

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2006 LBZ CCSB Leveled, Hypertech Programmer, 2008 LMM WT, 2008 Gasser WT
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207 Posts
Alright! Awesome I am going to return what I got and pick up the hypertech!
Start with the advertised diameter of the tire and check the truck speedo with a GPS speedo, then adjust tire size setting to fine tune it if necassary.
 

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Discussion Starter #6
Alright! Awesome I am going to return what I got and pick up the hypertech!
Start with the advertised diameter of the tire and check the truck speedo with a GPS speedo, then adjust tire size setting to fine tune it if necassary.
quick question if you don't mind, when the hypertech gets here. If the diameter does not work exactly do I go up in size or down in size get the speedometer to where it needs to be. Like if I go up in size does that make the speedometer go up or down?
 

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2006 LBZ CCSB Leveled, Hypertech Programmer, 2008 LMM WT, 2008 Gasser WT
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If speedo reads too fast, reduce tire diameter.

If speedo reads too slow, increase tire diameter.
 
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