32.15" approx.

(TxS = Z,Z / 25.4=Y,Y x 2= W, W+V= tire hight) where V= rim size, T= Tire width in mm., and S is the aspect ratio expressed in a persentage (70=.7)
275x.7=192.5, 192.5/25.4=7.57874, 7.57874x2=15.15748, 15.15748+17=32.15748


thats yalls math lesson for the night.

 

first thing id do is check 02 sensor, then check to make sure your cat is good. also if you hammer on it really hard look for alittle black smoke to coming out of it. this will indicate a bad injector dumbing gas ( giving you horrible gas mileage) i have one doing it right now. also does your truck look like its running rich? no power, alot of carbon on truck/exhaust system? also hows it running? is it useing oil? your plenum gasket could be bad also giving bad gas milage

 

Ok, I really appreciate all of the help, from everyone, I talked to the dealership before putting the tires on, so I know they don't effect anything very much, and I drove to green bay which is about 600 miles from me, I took the programmer off for one tank of gas, and then compared it to a tank with the programmer, it was slightly better with the programmer, I will change the O2 sensor this week, to give that a shot, and check the catalytic converter also, I ran Seafoam in the last tank of gas, and didn't get much improvement, and I will watch for smoke, thank you everyone for your advice
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As someone said before, its not the Hypertec nor the tires... I have the same setup on 5.2/3.55. The tires didn't change MPG noticably and the Hypertec gave me 2-4 MPG depending on if I was towing, driving city of HYW. My suggestion, take it to your dealer for a thorough "look-see". Good luck.