Portable Motorcycle Trailer - Slick Wheelie (Undertaker) 

your 21" knobby will not fit in the cradle. My 19'' rims for my Harley would not fit per my comments. May only be good for 17" or less rims

all of the bikes will lean, but the bike holds in place

Got that right! Backing up is challenging unless you can keep it straight. I only got it for emergencies, so can't comment on how it handles on the HWY

1000 lbs. Look up the Slick Wheelie on The USA Trailer Store for more info at: theusatrailerstore.com/the-original-slick-wheelie-motorcycle-hauler/ I'm pretty sure on the reviews, someone said they hauled their motorcycle on a long trip. I only had it for emergencies. Note that their specs state that the front tire cannot be wider than 5.5 inches, but I would say below 5.5" as I tried to mount the 5.5' rear tire of the Zero and it would not fit. It will also not fit a tall tire like a 19" rim wheel that was 26" overall (including tire) which was on my former 09 Sportster. Unfortunately, I sold my Zero and gave the Slick Wheelie to the buyer, so can't provide any measurements for the Slick Wheelie.

I mainly got it for emergencies. I actually only towed it for this video. Otherwise, it does the job for the right front wheel rim (around 17") and non-wide tires. I tried mounting the bike in reverse with the rear tire, but the tire was too wide to fit in the cradle.

@@stevofish7 Thank you.