2000 Chevy blazer zr2 4x4 2 Dr
 

Need help, I need to know what is the widest tire I can put on my stock 15" rims / does not have a lift

No more than 4 inches wider than the rim itself if I recall correctly. That would be 275 mm or 10.5 inches in common sized tires. However, plan on some rubbing unless you lift your vehicle and/or doing some trimming. Some tire shops may install wider tires, but most won't.

wide tires slowly kill wheel bearings. Avoid it.

What AJBert said.

FYI, if you can find them, you should be able to put 255/70/15 tires on factory rims with factory suspension and not rub. I had that size on my 96 Blazer for a few years. They look a lot beefier than the factory 235's, but still fit with the stock suspension and are around the same height as the factory 235/75/15 that my Blazer called for.