At lowest height setting the rack will clamp most common size spare tires in place. Shape of bed and bottom of rack hold it in place.
The rack Looks great and would love to use it in our ''ADOPT-A-TRAIL'' program ,but mounting on the lower bar is not a option for me being I have a bed box and would need a rack up high to clear the box in the bed . I see on your web site that you sell other size tube clamps and was wondering if another size could be used . I under stand You had made one or twenty the same way to sell for only location and you would like to sell them be for they collect dust .