Question on Tires

[Moyo]

Okay, I know this question is less related to bikepacking than it is to just mountain biking, but I'm a little green and imagine the people on here have more experience with fat(ish) tires and tubeless systems.
Although I currently run a set of 2.25 tires with tubes (on tubeless rims because the tires were free), when these wear out I'd like to get the best and widest tubeless tire my bike can afford.
I don't know enough about rim width and fatter tires, so I'd like to understand whether or not my rims can run fatter tires.

I say rims because I know the fork and frame are not an issue. The manufacturer's website claims a clearance of 2.3" in the rear and 87 mm (~3.4 inches) for the fork.
So if my rims are Stan's Flow 29ers, what's the widest tire I could reasonably fit on this bike?

[bartspedden]

While I don't own the hoops you are talking about I can compare rim width's with rims that I do own.  Your flow's should have a 28mm width, and a pair of Sun Ringle ADDs that I have are 30mm. I've run 2.7'' tires without any problems, but they are downhill specific.  I've never heard of anyone running 2.7s on a trail bike, so I'd suppose that 2.5s would fit just fine on your flow's. But it's pretty rare to need/want a tire that wide on a trail bike. What are you planning on doing with your fat rubber?

[chrisx]

any 29er tire made
Wtb 2.55 weirwolf tires fit a Flow
Racing Ralph 2.4 fits a Flow
Surly says their new 3 inch Knard will fit a Flow
maybe they did not say that ops

What fork  fits 3.4 inch 29er tires?

"But it's pretty rare to need/want a tire that wide on a trail bike. What are you planning on doing with your fat rubber?"

If you encounter sand along the trail.  Some times the trail turns into a dry creek bed for a few miles. A 2.55 is not quite enough for a river of sand.  

[fotooutdoors]

Surly says their new 3 inch Knard will fit a Flow
What fork  fits 3.4 inch 29er tires?

Many rigid forks will take that beefy of rubber; I measured, and my fargo fork would take the knard with room to spare (it would almost take a larry on 50mm rims, based on what I have read on the web).

As to Flows and Knards, I would hesitate to use that narrow of rim with that wide of tire.  The rabbit hole is almost twice as wide as the Flow, and surly's blog only mentions measurements on a P35.  That's probably the narrowest rim I would use.  If you consider "normal" widths, the ratio of rim width to tire width is usually less than 1:2.25, which would give a 34mm rim for the knard.
Check out the table at http://www.schwalbe.com/gbl/en/technik_info/reifenmasse/index.php5?flash=1&gesamt=27&ID_Land=38&ID_Sprache=2&ID_Seite=141&tn_mainPoint=Technik&tn_subPoint= for some more guidance (note that the chart on that page is referring to inner rim width, fwiw).