I need to know if i can put 305/70-16 on a 15x7", 5x4.75" lug pattern. Im not very good with the tire and rim ratio. But I want to keep my originial rims and I want to put 33's on my blazer.

 

Well the first problem i see is that you are wanting to put a 16" tire on a 15" rim. Now even if you did have a 16x7 inch rim you would need new widerrims anyways to avoid weird wear on the tires. I've linked to hanr3's wheel guide before and i still recommend that if any one has questions to consult it as it pretty much covers all your bases. Its pretty easy to find by using the search feature.

 

Well, first things first, you would need a 305/70R15 if you want them to fit on the stock rim. Just to help out, a 305/70R16 tire correlates to 305mm (12") wide at the tread, 70 is the aspect ratio, the percentage of sidewall to tread and the final number is the nominal rim diameter that the tire is made to fit. To get the overall height of the tire, you have to add the rim diameter to the sidewall height times 2. So the tire you stated is a 16" diameter rim and the sidwall height is found by multiplying the width (305mm = 12") times the aspect ratio (70%). So 16+2x(12x.70) = 32.8. On a 15" rim, a 305/70R15 would be a 32" tire. You don't want to put a 12" wide tire on a 7" wide rim...


To get to 33" outside diameter tires on a factory rim, your going to need to step up to 85% aspect ratio tires. So you'll need 9" of sidewall height. So you'd need a 265/85R15 which is one meety tire if it's even available... And even that is pretty darn wide at 10.5"