Minimum sized chunk of land for a decent trail loop?

It all depends on your creativity. I have a buddy who has 7 acres with a house on it and he has made one of the coolest single track loops I’ve ever riden. Another buddy has 5 acres and has built a really cool single track and endurocross track on it. I would say with 8 acres you would have no problem being able to developer a cool Mx track and off-road loop.

Go for it!
With some creativity, imagination, and effort you can have a great trail system on 8 acres.

I’ve built trails for 30 years and really enjoy it. I often remind myself: less trail work, more riding.

A small piece of land challenges you to make better use of space and creativity.

Tons of great resources available:
-Vital – Several threads about private tracks and some include trail pics also.
-IMBA – Moto and pedal trail design basics are much the same. The IMBA site has lots of resources.
-Pinkbike – MTB site with tons of videos and pics of great trails all over the world.
-Youtube – I really like the World Enduro Championship, British vintage trial, and Idaho trail riding vids
-Many state DNR departments have trail building info available

Tips:
-Less can be more: I have 26 acres and my trails are better than when I had 150 acres to work with.

-Change it up. It’s your place, if you build something and it doesn’t work out, change it!

-Mow it. Quickly add trail by mowing a path through areas with tall weeds or grasses. I have a spot with 5’ tall weeds that feels like riding through a tunnel and all I do is mow it every few months.

-Winding along. The funnest distance between 2 points is a winding trail.

-Alt lines. Add little lines that go off the main trail for more challenge (log hop, rocks) and then join back. You ride the hard line, others can stay on the main trail but you both have fun and stay close.

-Double mileage using trails you can ride both directions. A big downhill becomes a challenging uphill.

-Steal it. Use features from elsewhere, even if the terrain is different (Indiana ain’t Moab but I can copy rock stair steps like they have)

-Natural obstacles. Logs, rocks make great ride over challenges or use them to tighten trail width.

-Man made obstacles. Equipment tires and cement slabs have many uses and are often free.

Get good tools. Trail work is tough and your tools should be too. Some popular brands are Rogue hoe, Silky (hand saw), Stihl (saw, weedeater, blower for me). My tractor makes big jobs easier.

Work with nature. Know the lay of the land and work with it. Bench cut trails are cool but take lots of work and maintenance. Nowadays I try get the best trail I can doing as little work possible.

Focus on fun! I say “not the most trails, but the most fun trails”. They need to fun to ride as a payoff for the hard work of building them. I like mileage but prefer riding a fun shorter trail several times rather than a longer one once.

Sorry for the long winded post.

Good luck and post your progress if you decide to move forward with the project

I am on 5 acres up here in fordland and have a fun little loop to ride. Bring back the little kid imagination and your land just became endless. The great thing about it being private is, you can change it whenever you want. For me ill ride it one direction for a while till i get really used to it, then ill ride it backwards to change it up. I am not far from Ozark so shoot me a message if you need help breaking it in! Id be glad to come down.

I've got about 6ish acres of public land basically across the road from my house. Nobody else rides it, as most people out here are on quads and couldn't even get their bikes in to the trails (My entry point is kept as hidden as possible and the trees are too thick to get a quad in).
The time of year to really lay out your trail is as soon as the snow is melting (depending on location). For me, that is usually early April I can get out, clear out the dead fall from the winter storms, usually takes me a day or two, and then I try to add a new section every spring. Obviously, the first year you will spend a lot of time on trail work.

I've got a cheap poulan chain saw (this one isn't a lemon at least) and my weed eater has the blade on year end for thinning stuff out... Pretty much all I need.

I like to go for a walk this time of year to scout out new lines, it's easier to see before things start to grow. Walk the land, back and forth in straight lines about 50 yards apart, and mark cool features on your map on your phone and then plot out a trail that can link them all together. I know my spot really well so I already knew what this year's expansion was going to be. Incorporate the features that are already there. Logs, rocks, hills etc.
Even on the small parcel I use I have some tricky stuff. It isn't a "fun" trail, it's mostly slow 2nd gear, and I work on the things I suck at... Which is everything basically. Still, a loop for me is around 15 minutes and it's good training.
I'll be inviting some riding buddies this year to ride it, I hope that means I'll have less maintenance to do... But, that also ups the risk of the wrong person getting in there and cutting out logs and stuff like that.