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[can of worms] - : opened :

there are many different reasons to run a specific size tire.

If you got some time:
http://www.expeditionswest.com/research/white_papers/tire_selection_rev1.html

(In the Nutshell)
"When climbing a ledge with a jagged surface, the narrower tire will wrap the protrusions with more contact due to the increased deformation depth. The wider tire will rest on the surface of the protrusions and will have a greater chance of spinning (shearing)."




Skinny:
*Contact Pressure
*Rolling Resistance
*Frontal Resistance
*Rotating Mass
*Size Fitment
*Weight
*Airing Down

Wide:
*Improved Handling
*Greater Section width for flotation (deep mud/snow)
*Appearance
 

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tall and skinny will help you with gas mileage too.
 

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[can of worms] - : opened :

there are many different reasons to run a specific size tire.

If you got some time:
http://www.expeditionswest.com/research/white_papers/tire_selection_rev1.html

(In the Nutshell)
"When climbing a ledge with a jagged surface, the narrower tire will wrap the protrusions with more contact due to the increased deformation depth. The wider tire will rest on the surface of the protrusions and will have a greater chance of spinning (shearing)."




Skinny:
*Contact Pressure
*Rolling Resistance
*Frontal Resistance
*Rotating Mass
*Size Fitment
*Weight
*Airing Down

Wide:
*Improved Handling
*Greater Section width for flotation (deep mud/snow)
*Appearance
Can of worms for sure -

I was thinking about the diagram and it neglects the fact that not all tread patterns provide the same amount of tire to ground contact, i.e., a MT will have less rubber hitting the road than a street tire, so the pressure applied to the ground per square inch of tire contact is actually increased with a MT, given the same section width.

The website you point to also suggests tire widths based on gross vehicle weight (GVWR) and in the category of our rigs, he states that a 9.5 - 11.5 inch wide (235 - 295) tire is appropriate, depending on the surface to be driven on. I would also suggest that it depends on the tread design as I said above.
 

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I agree tread design does play a factor, but looking at the same tread design for both a wider size and skinny size, the skinnier still will form to the surface better.

Even with an agressive tread patter, the treads lugs will form to meet the surface. With a greater displacement of weight in a wider tire the lugs will less likely form with the surface.
Think snowshoe or boot. Laying on ice or stanind on it.

You can take the above picture and use that against a single lug rather than the whole tire.


Now again this is happening at the sub-mm levels, but its the difference of making the ledge or waiting for next year.
 

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I, too, considered a "tall, skinny" tire in an effort to maximize trail performance without the hit on fuel mileage that results from the additional weight and rolling resistance of 285/75R16 tires.

After some Google searches, thread reading, and telephone calls to two chain stores and my local independent tire shop, I came to this conclusion:

A 255/85R16 tire might be a great choice on an Xterra, but many manufacturers have discontinued that size and the very few tires still available in 255/85R16 tend to be more expensive than the 285/75R16 counterpart.

Also, many (most?) tire shops will need to special order them, which could be an issue if you are far from home and need a replacement.

Selection, price and availability favor the 285/75R16.
 

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I'd look for a 265/275 over a 255/285 from your post. I just posted on this a few days ago on the '33" tires/no lift' thread. Summary: 275/70/18's would have allowed me to run no BL and/or no metal hacking over the 295/65/18's I have with my set up. Both are 33's. Exact specs say the 275's are 33.2" and the 295's are 33.1". They're Duratracs. I have the 275 for a spare so I know that is right on. The 295's are 3/4" wider - all of it the tread (footprint). To do it over I'd go with the 275's. That's only 3/8" less on the outside (not as aggressive looking) and 3/8" inside (better all the way around) - 8.5" wide wheels with +18mm offset. Would have probably gained at least 1 MPG also, maybe two? Overall, 3" more rolling resistance with the 295's.

You might think about shock spacers and aal or shackles to get up just a little bit to run the tires and wheels you really want. Cheap and easy. BL's suck IMO and I have a 2" but to get just a bit of extra clearance for the least $ and hassle, spacers and shackles are what you want. Good luck!
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I'd look for a 265/275 over a 255/285 from your post. I just posted on this a few days ago on the '33" tires/no lift' thread. Summary: 275/70/18's would have allowed me to run no BL and/or no metal hacking over the 295/65/18's I have with my set up. Both are 33's. Exact specs say the 275's are 33.2" and the 295's are 33.1". They're Duratracs. I have the 275 for a spare so I know that is right on. The 295's are 3/4" wider - all of it the tread (footprint). To do it over I'd go with the 275's. That's only 3/8" less on the outside (not as aggressive looking) and 3/8" inside (better all the way around) - 8.5" wide wheels with +18mm offset. Would have probably gained at least 1 MPG also, maybe two? Overall, 3" more rolling resistance with the 295's.

You might think about shock spacers and aal or shackles to get up just a little bit to run the tires and wheels you really want. Cheap and easy. BL's suck IMO and I have a 2" but to get just a bit of extra clearance for the least $ and hassle, spacers and shackles are what you want. Good luck!
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i love my 275/70/r18 duratracks....
 

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I agree tread design does play a factor, but looking at the same tread design for both a wider size and skinny size, the skinnier still will form to the surface better.

Now again this is happening at the sub-mm levels, but its the difference of making the ledge or waiting for next year.
My biggest gripe is that the illustration WAY exaggerates the differences in tire deformation. Plus, the 255 is only 89% the width of a 285. so all we're doing is splitting hairs, not making a difference that would mean getting up a ledge...

[can of worms] /closed
 
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