I have the 37 Kreepy Krawlers. On an 8" Walker evans. Cause its a mechanical beadlock the outer tyre wall sits on the outside of the rim. So its more like a 8.5 inch rim as far as the tyre is concerned. To be honest they grip well in the mud but nothing I havnt seen a pro comp do. I also have a set of 38.5 swampers. They love slop. Side wall flex is real good too. The maxxis is a very stiff carcas. The crowning as FC mentioned is really bad. Have tried various tyre pressure but I really think they are not suited to a TJ. TJ's are too light for these tyres. Might be ok for your JK though. How much do the 4 door JK's weigh anyway? At 6 and 10 psi I cant get them to bag out at all.
On the road they roll around cause of the "ballooning" Might not be as bad on a 17" rim though. So in sayng all that you wanna buy mine?