I've seen alot of people have problems with bad vibrations from over-sized tires. Typically MUD tires are the worst for this. In my experiences, balancing them is almost useless. You can drive 50+ miles or so and they are way out of balance again. I've come across a VERY neat product that eliminates excessive vibration caused by large truck tires. It's a sand-like substance, that is placed inside the tire. It moves around in the tire, constantly keeping it in balance. I know it may sound strange, but it works!!! You might want to index the tire on a balancer first, by spinning the tire on the rim, trying different locations to get it where it calls for the least amount of weight. Mark where the valve stem was on the sidewall of the tire. Then break the tire down off the rim, and install the sand-like balancing substance. The packets the product comes in tell you how many packets to use for different size tires. 33inch tires and up, generally are what you want to use it on. Most shop supply dealers can get this product for you, especially wheel weight distributers.
Hope this helps some of you get smoother riding mud tires...

"Don't Laugh At This Truck Mister, Your Daughter Might Be In Here!!"
'78 F250 4x4/351w/NP435/NP205
lifted/"35 mudders
'78 F100 2wd/360/C-6/"9 inch
4bbl int+carb