I have a 2001 GMC Sierra 2500, the stock tires are 245/75/16.
I have found a REALLY good deal on a set of 275/70/16 tires. How much different are these and are they better or worse than the factory tires? The stock tires have that middle numer of 75 while the ones I have found a good deal on are 70, before I go out and buy them I figured I would ask on here to get some opinions as to what to do, thanks.

your speedo will be about 5mph off on the highway and brakes a bit softer do to the increase in rotational weight. Is this a diesel or gas truck?

8.1l gas/allison transmission. I guess the real question is are the factory 245/75/16 tires better for towing than the 275/70/16 which I'm thinking about getting?

Www.1010tires.com has a calculator that will tell you the exact differences.

Most folks can fit 285s on that truck. One of the biggest factors is your rear end ratio. 3.73, you will more than likely notice a slight lack of power in towing. 4.10, not so much. Only buy them if they are E-rated.

You can buy a DiabloSport or Hypertech Programmer to adjust your speedo setting. You can even adjust your shift points to somewhat make up for the adjustment in tire size as well when it comes to towing and acceleration.

275 and 245 is width in mm.
70 and 75 is the sidewall height aspect ratio.

Wider tires are actually better for towing. You will also see a drop in gas mileage as well.

Sydwayz thank you very much for the detail response, just out of curiousity why would there be a loss of power in towing if the tire is wider?

Loss would come only if the new tire is taller. I didn't actually do the calculator on those two tires though.

The new tires will be ruffly 32 inches tall.. Your stockers are ruffly 31.. So your only looking at about a 1''..


John jr

http://www.1010tires.com/TireSizeCalculator.asp

New tires would just shy of 3/4" taller, and over an inch wider. You will probably be fine.

However, not all tires are created equal, especially not LT tires. What are the new tires with the new deal? I'll never buy another set of Goodyear truck tires again. In my experience, they use much softer copounds and the ride feels like driving on spagetti.

That tire calculator definitely helps, so in reality even though the stock factory tires have that 75 in the middle( 245/75 16 which means the sidewall would be taller by the calculator the new ones with 275/70 16 have a taller sidewall? How does that work out? Sorry for the questions just trying to get a better understanding

By the way they are the ZIEX S/TZ model, I'm not too familiar with this so are these the correct tires or do I need ones that say LT on them?