What type of terrain makes an MTB mandatory? I'm somewhat new to biking, and I've been commuting to work on my new touring/hybrid bike for a few months now (it's a 2014 Novara Safari). I am very interested in doing some actual self-supported bike tours, but I'm unclear on what type of routes I can expect to tackle.

Obviously, I can do paved and gravel trails/roads, but will any type of single-track or dirt-path be unthinkable for great distances? I suspect anything with jumps is a bad idea, but that's probably true for any loaded bike. What other things should I look out for on these trails with a non-MTB?

As a follow-up, what can I do to improve my bike for these rougher paths? I have already installed Schwalbe Marathon Pro Tours (original continentals kept slipping in wet grass and getting flats at the sight of a thorn), which have some decent tread.

For context, I'm considering segments on the Ozark Trail in Missouri. If I can't reasonably expect to do this on my current bike, I'll be settling for the Katy Trail.
I think you would find the bike handles reasonably on single track, 4x4 tracks and dirt paths but there are a few things to bear in mind.

I'd ride single track but stick to trails graded easy.

Where an MTB would be mandatory would be anything above that. The following features would require a MTB (or at least no gear or being on a short ride ie. mud).


Gradient (up) - fine on a short ride, horrible on a long ride carrying gear.
Drops and Jumps - wrong bike type and not worth risking damage.
Rocks and Roots - you could do it but wrong bike type and not worth risking damage.
Switchbacks - more difficult when on a loaded bike.
Mud - infinitely more annoying when you can't have a shower at the end of a ride, worse if the options days away.
Gradient (down) - what impact will extra weight have on your brakes.


Upgrades wide to handle more off road riding I'd look at disc brakes and 32mm + cross tyres. Play with pressure until your happy.