I have a '99 silverado 1500 and I am looking to put a larger set of tires on in the near future. Stock wheels measure 16"x7". I am currently running a set of 265/70-R16 which are roughly 10" wide. I was wondering if it's safe to run a wider tire on the stock rim, say a 12.5" tire. I have a lift kit to install so clearance isn't going to be an issue, my main concern is if the stock wheels being as narrow as they are, will put to much strain on the tire's bead.

 

The sidewalls of any Tire, were designed to run vertically. ie: the width of the Tread and width of the Rim being the same. That produces the best performance from the Tire.

The wider the Tire Tread is compared to the Rim width, the more "oval" the section of the Tire is, so...

The more sway one gets side to side, reducing the "crispness" of control,
One must lower pressure in it, to realize even tread wear,
Lower pressure may cause a detachment of the Bead on hard cornering,
Lower pressure permits excessive compression and vulnerability to Road Hazards (chug holes/curbs),
The perception of Breaking and Power are negatively influenced by the larger size,
The offset of the Sidewall, may cause premature failure of the Tire due to excessive flexing (plys breaking/heat generated).

But, can you do it...
Yes, but I'd highly recommend you getting a 12x16" set of Rims.

 

Thanks a bunch, that is exactly what I was looking for.