From 265 65 18 to 285 65 18...Speedo/computer question

[stampede20]

2009 Silverado 2'' leveling kit, 1'' blocks, GM mudflaps.

 

I have pretty much made up my mind to put 285 65 18's on my truck from the stock 265 65 18 size. The only other size I considered was the 275 70 18's. I like the look of the wider 285's, but also like that the 275's are taller. I am trying not to get too wild on the size difference...hence staying with the 285's.

 

My question is:

 

I know my speedo will be off about 3% with the 285's (as opposed to 5% with the 275's). I would like to just leave everything else alone, and not bother with a tuner/programmer. I have a friend that did that for a year without any problems. Does anyone see a problem with putting the 285's on, and not using a tuner to adjust the speedo/odometer? I tow a boat and trailer in the summer, but not very often... I would say I tow 10-20 times a year(20 at MOST) with trips no further then 200 miles a trip.

 

I did the math, and if I drove 60,000 "miles" (according to the odometer with the new tires on without adjustment/programmer) I would have traveled 61,935 actual miles. I don't think that's too bad considering 1,935 miles is only a few months worth of driving.

 

I have also read about your shift points being off without a programmer to compensate. Is that a big problem? Is it very noticeable? I personally can't see it being a issue....but then again, I am the guy who wants the tires...but I also don't want to cause tranny/driveline problems. I will be keeping this truck until its dead.

 

Any input/experience?

[Stevens03]

Bumping from 265 to 285's are not going to cause a problem.

[Big Whiskey]

I haven't adjusted mine for the 285's....and I don't find it necessary. You can check your speed with a GPS. For example, I know when my speedo says I'm going 60 mph...I'm actually going about 61 or 62. 70 mph is actually closer to 72 or 73. Not a big deal. Also, the MPG on your DIC will be off (both the avg and instant)....but I don't worry about it too much. My 6.0 is pretty thirsty....so I don't keep track of the MPG that closely...or it makes me grumpy, haha. I noticed a little power loss when I went to the larger and heavier tires....but it still shifts just fine. My two cents....if you're planning to get it tuned for other reasons anyway, then might as well have it programmed for the bigger tires.....but, if you were just planning to leave it alone...then it will be just fine.

[RyanbabZ71]

1" blocks? You went smaller than stock? Just wondering

[snarkee]

I've always gone 285 and never had my computer re flashed. You won't notice a difference with shift points. I just hated the 2mpg I lost on the last truck. Its making me think twice about the upgrade on this truck now that I live outta town and gas is $$$ up here.

 

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[stampede20]

Yeah I'm not looking forward to the gas milage going down....but I have a little beater car I use for regular commutes. How many miles has everyone ran with the 285's? What kind of problems have you ran into related to the bigger tires? Anyone have problems with the 285's rubbing? I have asked in another forum, and people seem to think it will be fine with the RC 2'' level.

 

Not 1'' blocks! haha. The actual blocks are whatever size would make the truck sit 1'' higher then stock. Can't remember what size they were. I am going to be selling the stock 265 65 18's with 40,000 on them soon....if anyone is interested. Im in west michigan.

[Big Whiskey]

I've got around 25,000 miles on my level kit and 285's without any trouble at all. My tires just barely rub my mud flaps when I get stupid, but that's because of my aftermarket rims.