My Blazer has 235/75r15 on it now, i was wondering if i could fit 255/75r15 on it without any rubbing. And what is the biggest tire size i can fit without rubbing or modification?

 

30x9.5x15 is about it until you start to do mods.

 

You may rub a hair on the frame seeing how it is 10 inches wide. However according to 1010 tire size calculator, it is only 30.05 inches in diameter so you should be fine

 

I wouldn't see those being an issue. The only problem as jon said might be the width. If you do have rubbing at full lock though you could always crank your tbars a touch. that should ease the rubbing a bit.
And as DKS pointed out the biggest size you can fit is 30x9.5 on stock height. Some people have claimed they have fit 31x10.5 on stock, but so far it hasn't been proven with a real 31x10.5.

 

I don't want to hijack this thread but what do you mean by real 31x10.5. I have kumho 31x10.5 kl71 on my jimmy right now are these real 31x10.5

 

He means that others have stated that same thing, but their tires actually didn't measure out to be truly 31" OD tires.

Take your tires for instance. A comparison of the rim diameter (15") to the OD of your tire from the picture you attached reveals that your tires are actually closer to 29.5" OD.

 

Grab a tape measure and check the diameter and radius of your tires. Tires specs from different manufacturers can vary greatly.

 

Cool being he wad a moderator I thought he knew something I didn't. I hevent physically measured mine but they are kl71 kuhmo 31x10.5s

 

Ok obviously from my post above I can't type on my Moto Droid lol. I just measured and SWARTLKK you are correct my tires measure out to be 29.5 approx.. I just learned something new. Now, how can they claim to be 31in tires and only measure 29.5in? That would be like me buying a 12in ruler and it only being 10.5in long. Is there a way to tell which tires are actually 31in without measuring?

 

Who is to say why they are not 31" diameter, but some 31x10.5's actually are 31" OD. That is why we say that you cannot fit a true 31" tire.

Most off brand 31" tires are actually much closer to a 30" tire from the major offroad tire players and some are even smaller. It pays to check their spec sheet against actual measurements. Kumho states their 31x10.5R15 tire is 30.6" OD, but your measurement indicates otherwise.