I just got a 4x8 aluminum rim mounted with a Carlisle 18x9.5x8 tire and it sure looks like the bead wants to just explode off the lip of the rim. I think this has been done before with good results? Took four guys at the shop to wrestle the tire on and they kinda looked at me like I was crazy to have this combo mounted. I gave them a good explanation on how I was going to use it so that gave them a better understanding. Think the tire bead will hold when there's heavy side load?

A link to a couple pics:
http://www.flickr.com/photos/beaker69/

I have some 16/9.5/8 on standard plastic wheels and they have not popped off under side load. I would think you should be fine.

I think you should be fine! I have 21x12x8 mounted on standard plastic rims and they have not come off yet either! Even with massive power slides on grassy fields! I say roll with it. Now the Carlisle tire is more flat on top than most tires, but it should still be ok!

I've done the same with no worries

Thanks guys. Yes....Carlisles seem to be flatter on top, we'll see how I like them after I finally get rolling.

Magic 8 Ball said you'll love them. I run the same at low air pressure without problems.

I have 19X11X8 on standard plastic rims as well. And no problems as of yet.
Though I just got some sweet 10X8 rims to put those tires on.

I wanted to go with a narrower tire in front but couldn't find any thinner sizes that were the same height. Only in the kenda which is 18x8.5x8 but that only bought me one inch. This rim did narrow my front a little but still ended flat on top which I thought it would have rounded it out more. Doesn't matter much anyway, long as it works right?

I run the same rim/tire combo with no probs