I've built two of these trailers using the 40x48 trailer kits from Harbor Freight. One was the 8 inch wheels, one had the 12 in wheels. I converted the 8 inch wheels to 12 inch, and had to raise the fender. I also removed one leaf from each spring set for both trailers. The tongue was close enough to level with my hitch. under and inch off, towed them thousands of miles. But when someone would offer me 7-800 dollars for it, I sold them. Proper tongue weight is not important than perfectly level. Especially at that weight.

 

I'm not so sure about tread pattern being a big deal. Unlike cars or regular cargo hauling trailers, we don't have that much weight back there. At some point, speed and resistance vs. weight will cause the trailer to hydro-plane regardless of the tread pattern on these significantly smaller/thinner tires.

Riding back from Sturgis '15 through one of the worst nighttime rain storms I've ever ridden through (no rooms available for hundreds of miles)... at one point, I would have sworn the tar snakes would have taken me out, without the trailer adding a little more stability to the rear end. Sounds kinda crazy... but my bro riding beside me on his NightTrain w/the fat rear tire wholeheartedly concurred. I also found my bikes rear tire worn down to showing metal cords by the time we got home, so that obviously added to the rear ends instability. We had a chase rig along but he bailed on us right outside of Sturgis or I would have likely loaded up the bike or maybe just the trailer or at least had him take my ol' lady. Dude even had my tent in his chase trailer when he bailed on us... long story but after that, we aren't "bro's" anymore.

 

 

You may also get better handling adding 12 inches to the tongue. I usually replace the entire tonguewith one piece.

"According to the California Department of Motor Vehicles, a trailer's tongue length should be twice the width of its tires, but no more than 6 inches longer than the distance between the tongue and axle. Place a tape measure at one end of the tire and measure the distance between it and the opposite end of the tire. Write that measurement down on a notepad and write "Tire Width" next to it.
Measure the distance between the end of the tongue and the center of the axle. Write that number down on a piece of paper. Add 6 inches to that length. For example, if the distance between the tongue and axle is 40 inches, then adding 6 inches will make the overall length 46 inches.
Enter the "Tire Width" measurement into your calculator and multiple it by "2." This resulting number is the length the trailer's tongue should be unless it is longer than the length of the trailer from tongue to axle plus 6 inches. If that is the case, then the tongue should be the measurement you received by adding 6 inches to the length of the trailer from tongue to axle. For example, if the tire width is 48 inches wide, but the length from tongue to axle is only 46 inches, then your trailer's tongue length should be 46 inches."

 

Damn, responding via my phone makes me look silly! I adjusted....