right to the chase: How much wider difference in inches do I need to upgrade my tires from 4 inches to what to see a difference in float?
I am going with 9x18 on the rear. It looks like I can only go with a 5 inch wide on the front without a fork upgrade. I figure with airing down I can get 7 inches. Is it worth the effort? I buggy on sand [soft and rippled]
I am almost having an OOB experience when I hit the soft stuff!!:o

It really depends on the tire shape, some are really square cut IE car/go cart tire, some are more round like a wheelbarrow, a square cut 4-5" wide tire should give a little more float, but most guys go up to a 6 1/2" wide tire as a minimum. It may be worth getting a custom fork made up to run a matching 9x18 on the front.

One thing though, square cut tires tend to do weird things on a front tire when turning hard as they ride up on one edge.

I am going with a round rib tire set up. I saw the potential of too much grip with the square tire too. Plus I want to be able to slide in my turns!

I think I will upgrade the rears and then see from there. Thanks Pablo.

I've got to disagree with your assumptions about square profile tires

I run 22 x 12 square profile tires in the rear. They have had a "bead to bead shave" where they take off all extra trend and material. This makes them super light weight and very compliant in the sand. They have better float, and slide much more evenly than standard "Bigfoots".

Here's why:

1. A round profile tire only has the center section of the tire in contact with the sand (on your's, about 5") A square profile would provide the entire width of the tire. You'd get just as much float with 5" wide square profile tires but with half the weight! (deflating your tire is just trying to turn it into a square profile, but with lots of drag).

2. A square profile provides a smoother sliding edge. "Flat on flat" slides better than "round on flat". Understand that even square profile tires have a rounded edge, so its not like they're gonna grab. I can easily do sliding 360's on the hardpack sand!

I do however, prefer the standard round profile "Bigfoot" tire in front because of the tilt.

This isn't really my expertise but I understand how tires contact their surface. The round tires only have that 5 inch contact patch on hard sand. If the sand gets soft and that 5" sinks in a little, more and more of the tread surface starts to contact the sand, eventually to the point where the weight can't force the tire into the sand anymore. The rolling resistance is low when it can be and the flotation is high when it needs to be. Now, you can increase the flotation with the square tread by lowering the inflation pressure creating a concave tread face that sort of cups the sand, but as said above, that would create heavy drag.

All I know for sure is with the BF lights that have a narrower contact patch you can edge really good, easily enough to flip a BF hardcore over, with the Cadcat BFs I have on my buggy it'll slide forever, I can't get it to bite enough to tip up if my life depended on it.

I find even with the CadCat(full BF) there's no where near enough grip for my liking. As for the square tire being funny, I was thinking of the front when you bank it over on a hard turn and ride it up on one edge.

As far tire contact dynamics go. Soft sand has unique properties. Contrary to what you may think, a Bigfoot's performance is not the result of it sinking slightly in the sand.

Bigfoot's perform well is soft sand because of two reasons

1. The larger, wider tire has more contact area and more importantly...

2. The larger volume tire allows for lower tire pressures, which make the tire more compliant with the sand.

The logic is that air moves out of the way faster than sand, so its much more energy conserving for the "tire to conform to the sand" rather than have the "sand to conform the tire" This is also why Bigfoot's are bald, not treaded.

This is why buggiers tend to lower their pressure if running in soft sand, knowing that an overly inflated (really hard) Bigfoot will perform almost as badly in soft sand as standard barrow wheels.

Here's an interesting fact. Unlike concrete or hard dirt, a standard barrow wheel pumped up to its max pressure will actually have MORE drag in HARD PACK sand, than a moderately inflated tire. (try it out) Why? Same reason. The max inflated tires have no compliance and end up having to deform the sand slightly instead.

So here's a trick for all of you. If you are riding on hard pack with barrow wheels, and you find that your tires are making diveted tracks in the sand, lower you pressure. You'll get less drag and higher speeds!

And hey Pablo ... Good to see someone else promoting the advantages of square profile tires. I have used them for years. "Its Hip to be Square!!!!"