15 16 and 17 inch rims all have 90 degree bead,while 16.5 has 45 degree bead.thats why it is not a good rims to air down for wheeling.i have gone down to 15 lbs and would not go any lower.you can get the inner beadlock which is basically a tough inner tube and they seem to work pretty good holding on the bead.i havent seen a review on them in a wile though.