Looking at your sig, I am assuming you wheel the jimmy. 39.50's wow! You should have a difficult time making it through any of the trails around here. Bobcat will be the most difficult for you but only because the trail is sized more for a mid-size. I have seen a few full sizes out there before though so I know it can be done as long as your are not worried about scratching the paint or taking some minor body carnage.

My brother used to have an 89 k5 on 38.50's that he used to wheel and didn't have trouble making it through any of them. He never went to bobcat though.

I'll definately let you know the next time that I head out.