I think they work fine on the street. Not the tire you are going to slap on your gsxr750 and drag knee with, but if offroad traction is most important, it's what I use.

 

I’m a 57 yo guy with only a couple years off road under my belt so consider that with my response. I ride my KLX primarily off road in some pretty steep and tight trails. Most of my riding buddies are in dedicated enduro machines.
I’m running Pirelli Scorpion XC’s mid soft front and rear. They work good enough on the road (I typically only ride to the tails max 60 mph.) and seem to work good enough in the trails. Our trails here are pretty hard packed with rocks and roots. Next tire change I’m probably going with something a bit softer, and maybe not DOT approved. Local LE is pretty chill about the DOT requirements and I’d like better traction off road even if it means a bit less wear durability. We’ll see.
Best change I made for trail riding was a change to 13/50 gearing. Made second and third gear way more usable off road keeping first for the super steep stuff. Also helps me ride higher in the Rev range where the 250 seems to shine.

 

Thanks for the feedback guys.

 

Not earth shattering but went with a MT21 front and a D606 rear. Will be wringing out this spring. On KLX300 and son's KLX230.

 

My D606 is wearing fast. I am going to try the Kenda or the Scorpion next. May swap out the front too just to see if I like either option better on the front.

 

My take on the 606 vs Trackmaster on the KLX.

The 606 is a taller and heavier(not good on the klx), does not have much for side ***** so slides out more on turns on gravel roads, is ok for mud.

The Trackmaster has shorter sidewall(important to me to touch the ground), less weight for the motor to pull, great in mud and roots for a DOT tire, I lean mine over on the street probably more than I should but have never let loose. Cost less than a 606 but you will go through 2 trackmasters to 1 606.

 

Great feedback, thanks!