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Discussion Starter #1
I plan on installing 285/75 tires from my current 245/75 and was wondering what negative effects I will experience by not tuning/calibrating for the tire change? The only programmer out right now is the Bully Dog Power Pup, but I want to wait it out for other companies to release theirs. So if I installed the tires for now until I get a programmer, what am I risking? I'm sick of looking at my 245/75 tires! Thanks.
 

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Discussion Starter #2
By the way, since I'm waiting for other programmers to be released, is there any other way to calibrate for 285/75 tires in the meantime or even permanately?
 

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Besides you're speedometer and odometer being off you won't have any other problems. You'll notice you have a lot more traction, better looking truck, and slightly less power with the bigger tires. Your rpms will drop lower on the freeway too. Not sure what you'll be turning though because you've got one more gear than me.

On the other hand I've been really happy with my bullydog tuner so it wouldn't be a bad choice to go with.
 

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Yeah, you can get one of those truespeed units. I think superlift sells them. Google truespeed you should be able to find it.

My bad, I googled it and couldn't find it. Here's the link I guess I misspelled the word.
 

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Discussion Starter #5
Will my speedometer be slower or fast? Will my odometer put more or less miles on than it should? I assume my MPG meter will be off as well?
 

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Your speedo will read too slow as the tires are turning slower to go the same speed. Longer circumference...anyway too much info. This means you'll be registering less miles than you actually travel and once you but bigger tires on your MPG meter will be forever worthless. Even more so once you put a programmer on the truck.
 

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2000 or so rpm @80 mph.speedometer will read 7-9 miles per hour [email protected] 70-80mph. and it will put less miles on your truck. and you mpg will go down, that is what i have experienced. I took mine to the dealer and had them reprogram the abs to 265-75-16 like on the 1500's. just do it, you will love them, i sure do. 285/75/16 bfgoodrich Mud terrains. hope this helps.
 

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Well that's somewhat good to hear as I wouldn't want to put more miles than I was actually traveling. Any idea how much it will be off so when I do put them on, I know how fast/slow I need to go for the speed limit. Certainly don't wanna guess and get pulled over. Hopefully the MPG won't go down as I baby the truck anyway.
 

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Do you know anyone who's got a handheld gps you could borrow? That's how I calibrated my speedo since the tire sizes in the bullydog didn't seem to match the speeds up right. Go out and figure out how much lower it reads at 60mph and you'll be able to figure out the percentage and you could figure out any of the other mph's you'll be off at too. You'll get used to it after a while and then you'll find yourself driving too slow in other cars ;)
 

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From experience and what others have posted in other threads, I think its safe to say you will read about 7-8% slower than you are acually going, so until you recal, just ad 7% (spedo at 60 add 4.2 = 64.2) just remember that it is a percentage, and the faster you go the bigger the diff, 100 mph = 107
 

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When I first got my 06 I had some 285/60/18's installed and found that with my GPS, my speedo was right on the money, this tells me that the speedo was a bit fast with the stock tires. My 285's measured 1" taller than the the stock 245/75/16's.

Now I have 33/12.5/18's and my GPS says I am 4.5 mph off at 70 mph (slow). And my 33's are a bit taller than a 285/75/16.
 

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The dealer can program speedo for 285 75r16 tires...
 

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The dealer can program speedo for 285 75r16 tires...
Exactly, Why not let the dealer program the tire size in for you. It will calibrate the speedo and make the fuel info more useful. I put 255's on my truck last week and drove it 2 days without the update and I realized immediately that the trans shift points were way out of sync, making the truck sluggish and in the wrong gear at times. All of this went away after updating the tire size in my PCM with a tech2...Ask your selling dealer to do it for free and if not spend the $ on labor, you will be glad you did.

my .02

(yes I work in a dealership service dept and this is not a self-serving post...just helpful info I thought you would like to know..:) )
 

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So you're saying I can go to my local dealer and tell them that I just intalled bigger tires on my truck, will you cailbrate my computer for it AND they should do it for free? I've read that they can't calibrate for 285/75, are you sure about this?
 

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Just go with 265-75-16. You will get a better ride, no loss of power and better mpg. And they look just as good to me. No modifications necesssary either. When you are doing 65 mph you will really be going 67.5 mph. You can get the dealer to recalibrate the speedo or just add about 4 percent to the odometer for actual miles driven.
 

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I have 265's and they are 2mph off. I can live with that, so I have not done anything with it, and won't. That is not enough to worry about. A dealer will charge you to reprogram unless they are extra nice. If you don't have a GPS, or anything like that, have someone pace you in a stock vehicle. Call them on the cell phone, and set your cruise on a specific number and see where they are when you settle down. May take a few miles. I have even had a cop do it with a radar gun before.
 

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They can only do up to 285 75 r16..
 

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So you're saying I can go to my local dealer and tell them that I just intalled bigger tires on my truck, will you cailbrate my computer for it AND they should do it for free? I've read that they can't calibrate for 285/75, are you sure about this?
Yes, a calibration is available for 285/75r16...I just did it to mine since no 255/85r16 choice (same OD as 285/75).... If they do it for free or not is their call (depends on how well you know them, how nice they are, how much they want your service business, ask your salesman to ask for you or ask the service manager to do it for you while you get an oil change) or worse case you pay their labor charge to do it.

My dually had 215/85r16's and I upped to 255/85r16's ( 3" difference in height). This difference was dramatic enough that the transmission was in the wrong gears most of the time, making it very sluggish...Programmed the PCM with 285's as the tire size and everything is correct now...

Good Luck.
 
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