Looking for confirmation if info

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XCELLR8

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I was at the dealership today asking about getting my computer re-calibrated after getting new wheels and tires. The advisor did not know anything, so he called the parts guy. I was told that the Rams will learn and adjust their computers up to two tire sizes from stock without having to recalibrate. I had the 17s with a OD of 31.8 and the new tires have a OD of 32.5. With what I was told I could go up to 32.8 (285/70/17) and be OK. I would like to confirm if this is true or not with the trucks computer as I doubt its true.
 
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shipmasta

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XCELLR8 said:
I was at the dealership today asking about getting my computer re-calibrated after getting new wheels and tires. The advisor did not know anything, so he called the parts guy. I was told that the Rams will learn and adjust their computers up to two tire sizes from stock without having to recalibrate. I had the 17s with a OD of 31.8 and the new tires have a OD of 32.5. With what I was told I could go up to 32.8 (285/70/17) and be OK. I would like to confirm if this is true or not with the trucks computer as I doubt its true.
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I dont know if that is true or not, but I had my dealer re-calibrate my tire size to 35s. I think they just charged me for a 1/2 hour of labor.
 
jlb

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I don't see that as very likely. The only references the truck would have for calculations (to make the adjustments) would be the differences in rotational velocities during a turn, but there are only 3 wheel speed sensors which would average the two rear wheel speeds, and then knowing the two fronts make a calculation, but it would be based on data that has a lot of potential variation...

I think whoever told you that is full of crap just because of the intricacies involved, but truth be told it is possible, just not very reliable...
 
TylerB

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Your part's guy doesn't know what he's talking about. These trucks do not learn their new tire sizes on their own, only way the truck way to change it is with a tuner programming the new size or the dealer programming it. I suggest a new dealer that hires knowledgable staff.

By the way, the dealer can only program for stock size tires. Shipmasta have you checked you're speedometer vs a hand held GPS unit? The GPS in your radio will not work for this as gets it's speed from your speedometer and not via the satelite.
 
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shipmasta

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Tylerb said:
Your part's guy doesn't know what he's talking about. These trucks do not learn their new tire sizes on their own, only way the truck way to change it is with a tuner programming the new size or the dealer programming it. I suggest a new dealer that hires knowledgable staff.

By the way, the dealer can only program for stock size tires. Shipmasta have you checked you're speedometer vs a hand held GPS unit? The GPS in your radio will not work for this as gets it's speed from your speedometer and not via the satelite.
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Yes I confirmed that the speedo is correct. Checked it both by hand held GPS and a radar enabled speed limit sign. Before going to the dealer they were both off by the same amount, after dealer reprogramed, speedometer, radar enabled speed limit sign, and GPS all matched.
 
Stangshcky12

Stangshcky12

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That change in size will hardly create any difference and since all speedometers can be up to 3mph from the factory you wouldnt notice much of a difference
Going from a factory 33 to a 35 would only throw the speedo off about 3.5 mph at 60 mph
 
Thor09

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The biggest tire size the computer can be changed to since the 09s came out was 275/60-20 or 33". Unless you have a tuner or programmer...
 
1500ram12

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I put 285/70R17 and never had to recalibrate the speedo. Never change the tire size on the bullydog

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