Towing Issues: towdollies, tow dolly, railroad crossings

Question
my tow dollie has 15inch wheels yet my car a ply voiager has14. hhen I loaded the van there is only a 3 3/4 inch clearence from the road to my bumper .(is that enough clearence?)

Answer
Well, you have encountered the problem which us tow truck drivers run into daily...

As a general rule (this is a suggestion which I use) if you can stick your foot under the back bumper with your shoes on and it goes all the way to your leg area (the highest part) they you have enough clearance for towing, unless you are on one heck of a rough road or have to cross some big speed bumps or railroad crossings...

unfortunately you will not be able to adjust the height with the tow dolly, like we can with the tow trucks but one thing to remember is that your tow vehicle (what you are pulling the tow dolly with) might be taller than the normal hitch level.  This would make the front of the tow dolly higher than normal and the rear would be lower...

Check that issue out and see if that might be the case but the distance you mentioned sounds about right to me.