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Discussion Starter #1
I was sure I could find a post that covered this topic, but no luck. What is the cheapest way to recalibrate the computer for a tire change from stock 245 to a 265? With the new computers and not a VSSB I think it should be easy, just don't know how.
 

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go to dealer....they can re-cal for 265s.
 

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Commissioner Gordon
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2 in your sig can be done with a Tech2, the '95 I don't remember off hand.
 

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Discussion Starter #4
I was hoping a Tech2 would do it, now just need to find one around here(Boise ID).
 

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Commissioner Gordon
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Swing down here, I'll do it for ya. It only takes less than 2 minutes, other than the xxx hour drive:D
 

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How about my rig? 2004 GMC Sierra 2500 HD? The dealer said that they can't do it, only the 1500s. Any ideas on aftermarket tuners? I have the 285s and I'm off about 3mph at 60.
 

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you cant fix it with a tech 2!!! You can fix the ebcm/ehcu (abs) calibration but not the VSS output to the speedo.


need a tuner or EFILive.
 

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My speedometer was only off 2mph at 80, when I went to 265's. For that difference, I just lived with it, because it wasn't enough of a change to spend the money on changing.
 

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Tire size 265/245

Does it affect any thing besides the speedodmeter .
 

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It changes how much ground you cover for every revolution of the tire. The 265 is bigger, so it covers more ground/rev than a 245. Its sort of like having a higher gear in the rear end. It is only about 4% difference in speed. Probably wouldn't notice much difference. 265 sure look better than those dinky donuts they put on the 2500s
 

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I have 285x75x16's on my 01 2500HD and I'm off about 5-6 mph at 45-50MPH and when my speed-o says 65MPH the truck is actually doing about 73MPH,at 75 I'm really doing 85MPH. I just cant find anyone to run with me when my speed-o tops out to see what I'm really doing then. I have/use the "Superchips" programmer and it will eliminate the speed limiter but with the Allison trany i cant change the speed-o and the dealer told me also they cant help/fix it ether. In our old trucks you just put a gear reductioner on the trany and the speed-o cable into that and it was fixed but not with computers. Have a friend run next to you at all diff speeds and take note at you speed-o speed verses your true speed and ether right it down or memorize it or with time you will get a ticket because of it and not even mean to. The plus side is, own the truck long enough and it will show much less millage then you really have when you do sell/trade it in. If you do find out how to change it please make a BIG posting here so the rest of can do it to.
 

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I have the same problem but when I bought the truck it had 315/75/16......................my tranny holds shifts longer when stepping on it nad have already had to rebuild it once.......i have a 4 inch lift on it and dont want to downsize too much but is there a way to recalibrate the vssb for correct tire size because i highly doubt the guy did it before me????will the superchip reprogram it for me as I had read something about the 1995's which it is a mechanical device......hope someone can help here...thanks.....i feel like it is throwing off my timing to because I have codes of IP errors and I am not sure if it is the tires throwing off my shifts which then throws off my fuel consumption....when my gf was doing 65 next too me my speedo read 58..........had this before the grease conversion as well
 

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I have 305/70/16's and at 55 on the speedo it is 62.5 on my gps.
 

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Discussion Starter #15
I was hoping for something a little newer like the 2000+ generation.
 

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I just emailed the guy that has the web sight given above for info on newer trucks with bigger tires and I'll let all know when and what I hear back from this guy. As I have a 01 with bigger tires.
 
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