i to plan on running a narrow 34 35" tire, they are just hard to find.

 

there are lots of us!

My biggest issue with the 255/85R16 is that it is a touch to narrower than I am comfortable with on 16x8 wheels. I wish that the bridgers were a 16x7.5 and it would make decisions so much easier.

 

Unless you just get those Interco 34x10.5/15 or 16 or 17" tires I posted earlier.

 

I do way too much highway to go with a Bias Ply tire.

 

Are you set on a Mud Tire, or would the BFG AT ko be a good choice?

For a DD that see's a lot of pavement, the AT ko is hard to beat...I've been running them on DD's for ever....I have ~ 80 K on the current set , and about 1/2 tread...but in a 34"-ish diameter, you'd have to get ~12.5" section widths.

If the bias ply issue involves handling, most of the pizza cutter mud tires are going to suck big time anyway.

But, Interco has the SSR (Radial) in 35x10.5/17 and 33x10.5/17 (The 33 is more than 33")

etc....

BTW - The fatter tread does better on the road, much better handling and braking, more stable/less weak kneed, etc....and off road as well....better flotation, more traction, etc.

Plus, merely going to a 12 or a 12.5-ish ratio opens up a world of choices.

 

*edited for clarify*
First of all, many thanks and much respect for Scott Brady at Expeditions West for his wealth of information (and great website). Please pardon my not-so-technical rambling. I'm too lazy. Also, thanks for this discussion - I'm sure I'll learn much....
Oh yeah, Scott, nice pics of the boojum trees. I still remember my trip down through Baja and the smell of the boojum (deadfall used to camp fires).

I love this! Intelligent discussion!
I'll expand on this later (going home now).
But remember that the idea of a narrower tire having the ability to flex down into the groves (see the graphic previously) is not complete. Remember that a shorter (narrower) rod (tread/belt thickness) of a lever won't flex as well as a longer (wider) rod given the same thickness. So, what I've experienced is that the narrower tire doesn't comform (deformation) over a rock that well. Also, radials don't appreciably increase their front-to-back contact patch much (bias ply tires do that).

So, you have less contact patch area which is less flexible riding on top of the ridges. There's a decrease in mechanical keying, deformation and also less adhesive surface, etc. Also, remember that the wide tire may have less downward pressure per square inch, but there's more square inches of tread (keying, momentary bonding, adhesion, friction, etc.) working for you.

My argument is that a narrower tire just has less tread (the thing that grips) working for you.

 

Good points.

Plus, the tire tests that were done comparing skinny to fat treads concluded that depending upon the rig and terrain, there were no terrains that the skinnies were superior on...but on rocks on a light rig, they were fairly equal.

If the rig was heavier, or on any other terrain, the wider tread won....even on snow and ice.

The reason is that MT's have tread BLOCKS, which act like cleats, magnifying ground pressure and traction points across the tread face...and a skinny tread just has fewer traction points to grab with.

That's why soccer shoes don't have just one cleat...they have a few scattered about the tread, etc.

The old idea that a wider tire was worse on snow/ice was based upon the older less aggressive tire designs, IE: No tread blocks, or elements too close together, etc.

Its all about sipes and rubber compounding now.

The old idea that a skinny tire will "Dig down for traction" was popular as well....except it really only applies to dirt roads with a bit of mud on them, and hard ground beneath that.

In reality, the skinny tire does dig down, and then - can't climb the wall in front of it, and gets stuck, because it had too little flotation.

Of course, there's a point of diminishing return for fat, and skinny treads...depending upon the weights and terrain, etc...and turning radius, etc.

Too fat, and you can't turn tightly for example.

That's primarily why people who offroad for a living use pretty much the same sized tires...they want to win, and they've arrived at solutions that get the job done.

 

I have to disagree on the snow/ice comment. Yes, a wider tire with siping and a good tread will do better on ICE, it's just simply a matter of more rubber on the ground for traction. But that argument doesn't hold true for certain snow conditions.

There are SOME snow conditions that a wider tire works very well for, such as a drier deeper snow which will adhere to itself enough to allow for traction, and the extra flotation can keep you from getting high centered. However, if the snow is wetter, and won't give you any adhesion, the only way you're moving is to dig down to the surface that the snow rests on. This is where a taller narrow tire is invaluable. A wider tire will just spin, and get clogged with snow. I'd rather have a tire that will dig down and keep me moving than one that will float over the snow.

Some people will make the argument that having the flotation will allow you to go through deeper snow, but seriously, if the snow is that deep, why are you driving there? Just the the snowmobile out!

 

No, the point is that you can just drive on it...you don't need a snow mobile...and, its typically ice beneath packed snow, not dry ground anyway...so the dig down for traction...but still have the traction to climb up over the stuff you just dug down through, and is now a wall in front of your skinny assed tire...so that you can continue to roll forward.



If its icy...you want studs...Blizzack type rubber compounds with a gazzillion micro-sipes, etc....work well too.....but, the more traction surface, the better the traction.

A racing slick presents little or no traction surface though...you do need points of contact that have grip.

 

Okay, not going to argue the studs/Blizzack comment, no dispute there.

As for driving over the snow...... if your tires float you over the snow, which is what you are saying is desirable, the only thing that you have for traction is the snow itself. There are times when this works quite well, the snow adheres to itself, and you motor right along. I think this may be where your comment on the packed snow comes from (I actually agree that a bit wider would be better on a packed snow situation), but I'm not referring to packed snow, I'm talking about loose/fresh snow. Regardless of the tire you run in that situation, you are going to have a lot of rolling resistance because you WILL sink in. With that resistance a wider tire that bridges the snow will often "break loose" and now you're fighting the rolling resistance of being a foot deep in snow AND trying to get snow to stick to itself so you can get enough traction to keep moving. In that situation a skinny tire will dig down and hit something solid, even hard pack snow or rough ice at the bottom will provide more traction than the snow that is bridged under a wide tire. In this instance it has been my experience that the extra rolling resistance of being a bit deeper with taller skinner tires is negated by having something solid to grind rubber against.

BTW, I'm really enjoying this debate, making me think critically about some of these things.