Ok I know that this has been asked before in many different ways but haven't found a thread that addresses my situation so here i go:

2006 GMC Sierra 2500HD Crew Cab Duramax 4wd 3:73

The truck has the stock 245 tires and needs new tires. Im wondering how big of tires we could go to without sacraficing fuel economy. I have never kept a vehicle long enough to put tires on so this is really a new experience. Im not sure what size means what on the tires.

Any inputs appreciated.

 

biggest tires possible or biggest without sacrificing gas mileage? define sacrifice... 285/75/r16 will fit comfortably but i personally think 305/70/r16s look better on 2500hd's...

the first number is the width of the tread in millimeters. the second number is the aspect ratio (70 means 70 percent of 305... as in the sidewall height is 70 percent of 305 millimeters) the last number is the rim size. the r means radial.

if you google metric tire size conversion there are lots of sites that can convert sizes into standard.

 

I know that by going to a bigger tire I can increase my gas mileage to a point, but after that it peaks and starts to decrease. If getting tires any larger will hurt fuel economy. we will just stick with 245's

 

at least get a 265 75 16 it won't affect the mileage, those 2500 with 245 look wimpy. Personally I would get at 285's under it

 

I've always found the bigger the tire, the worse the mpg. I know because I have the max on my silverado - 285-65-18s.

 

at worst you'll lose .5 mpg in my experience. i jumped from 235/75 to 275/70 to 265/75 and i haven't noticed more than .5 mpg difference.