As long as you put the right amount of bbs in the tire its fine. I've been balancing tires that way for years, everything from the little 235/75-15's I had on my XJ up to 40" Swampers, never had any vibrations from any of them.

 

how do you know what is the right amount?

 

I use this chart:

http://www.innovativebalancing.com/BigTirechart.htm

 

according to that chart, unless my math is off, and it's possible because I am sick, I would only use like 11-12 20gram airsoft BB's... that doesn't seem right...

 

wait, does 28 BB's sound more like it?

 

33x12.5-15

 

wait... when it said 12 and 20 gram, is that .12 and .20 gram? I don't do airsoft so I have no clue

 

The bbs I got are .2 grams each.
So, with your 33x12.5', they take 8 ounces to balance. If my math is right, that's 1120 bbs per tire.

Don't worry about counting them out, put them on a scale and weigh how much you need in each tire.

 

I don't have a scale that goes down that low. I think I'm just going to use steel BB's. A steel BB is 5.28 grains. 3500 grains is 8 ounces, so 662.87879 steel BB's would be 8 ounces. I think I'll throw 663 BB's in there and it should be close.

Plus with steel BB's, if I ever had a reason for taking them out, I could just tie a magnet to a string and drop it down in there lol

 

If they aren't stainless, they will rust.

 

Well I'm feeling better today, therefore my math skills aren't as lacking. Looks like I would need 226.8 grams of airsoft BB's which if I used .20 gram BB's I would need 1134 and if I used .25 gram I would need 907.2