Why skinny tires

[Desolation]

Sitting here around the fire, perhaps a pint of something 30-years old and for me I think a fine 50-Ring, yes, yes I'll take the down wind...

So I've been a-wondering, the Expo community tends to a skinny tire.
Having some experience with various widths of tire and having passed tens of thousands of miles under various tires and vehicles over the past 3 decades I am wondering why? What is the perceived skinny on the skinny?

In most cases I can only reason that is is some kind of tradition throwing back to when there simply were not good specialized off road tires, or even good road tires, and the look established back then, over rides the function today.
Then again what do I know?:coffeedrink: I'm sitting on the down wind side of this fire

Oh, here's that pint, sorry got to talking there....
:1888fbbd:

 

[Nullifier]

Sitting here around the fire, perhaps a pint of something 30-years old and for me I think a fine 50-Ring, yes, yes I'll take the down wind...

So I've been a-wondering, the Expo community tends to a skinny tire.
Having some experience with various widths of tire and having passed tens of thousands of miles under various tires and vehicles over the past 3 decades I am wondering why? What is the perceived skinny on the skinny?

In most cases I can only reason that is is some kind of tradition throwing back to when there simply were not good specialized off road tires, or even good road tires, and the look established back then, over rides the function today.
Then again what do I know?:coffeedrink: I'm sitting on the down wind side of this fire

Oh, hears that pint, sorry got to talking there....
:1888fbbd:

less tire wieght and width = less rolling resistance = better mileage. Hieght gets you more clearance reguardsless of width and most of the flotation achieved by airing down is accomplished by the diameter of the tire rather then the width. Scott has a write up about this on www.expeditionswest.com

 

[Desolation]

I've read it, well written.

 

[Scott Brady]

Less rotating mass- Easier to start and stop
Less reciprocating mass- Easier to dampen
Less wind resistance- Better economy and range
Less rolling resistance- Better economy and range
Easier to fit a taller/narrower tire with less lift
Lighter spare
Lighter tire
Lighter wheel
Less unsprung weight
Less weight and leverage on steering components, bearings, etc.

In terrain:
1. Less frontal resistance in mud and sand. Where is most of the increased contact patch (for flotation) gained? In the length, not the width. Tall and narrow allows for more length and greater deformation with less resistance.

It is as simple as understanding the coefficient of friction (COF), which is (Ff = Cf x Fv).

Ff= Friction Force
Cf= Coefficient of Friction
Fv= Force Vertical

As you make a tire wider, you reduce the Fv over a larger area, but gain Cf. As you make a tire narrower, you increase the Fv, but reduce the area of contact, which lowers the Cf. It is proportional, though there are times when the material interaction (lets say a drag tire on concrete) favors Cf, but those conditions rarely exist on the trail, on a perfectly flat surface. So, if a wide and narrow tires benefits with relationship to Cf and Fv are proportional, than the decision must be made on other factors, like weight, resistance, etc., as listed above.

Now of course, there are limits at both ends of the spectrum. Too narrow of a tire, and the torque applied to the surface, even with extremely high Fv (which a super narrow tire would have), would exceed the rubbers ability to resist tearing. Literally, burning rubber.

It is all a balance, with tires for most of the trucks we drive being ideal in the 9-11" wide range.

Big, fat tires are only for show trucks and tundra buggies. An expedition vehicle has an emphasis on simplicity, economy, durability and safety, none of which a 35x14.5 will give you. . .

 

[hochung]

Big, fat tires are only for show trucks and tundra buggies. An expedition vehicle has an emphasis on simplicity, economy, durability and safety, none of which a 35x14.5 will give you. . .

Scott, I think Desolation already knew that... 30 years of experience means something, right?

Now the REAL reason for me: I just love the way they look.

 

[Spur]

Also, you're able to have both to a certain extent. You can make a skinny tire fat by airing down, but you can't make a fat tire skinny by airing up.

I'm curious if there are other variables. Does the weight of the vehicle affect a choice in tire width?

 

[Ric]

I do more rock crawling, from what Ive seen, meaning the pros, the competition crawlers, factory teams, they use wider tires from what Ive seen anyways, lol IMO the skinny tires looks like they would be more top heavy on the street, whats that saying, "wider is better" :sombrero:

 

[Spur]

Also, you're able to have both to a certain extent. You can make a skinny tire fat by airing down, but you can't make a fat tire skinny by airing up.

I'm curious if there are other variables. Does the weight of the vehicle affect a choice in tire width?

I answered my own question with the chart that Scott put in his research paper. Looks like 10.5" would be about right for the weight of my truck. Thanks for putting in the effort and posting it on the web. It's a really great resource.

 

[KevinNY]

I am loving Ho's honesty.

 

[troy]

I didn't see this mentioned, but on icy roads a skinny tire can be easier to control. I'm sure it has something to do with the correct vehicle weight for the width as stated in previous posts. Wide for flotation in deep snow is good, but most winter driving is done on snow/ice covered roads here in the upper midwest.

Also, the "wider is better" philosophy applies more to track width than tire width. Tire width is great if it is a sports car on dry pavement, but gravel, sand, mud, snow I prefer a slightly narrower tire.

Just my opinion from personal experience, but I'd stick with Scott's scientific theory as the true reason for skinny tires on an expo rig.

Troy

 

[Big Bear]

More PPSI (Pounds Per Square Inch)

 

[jh504]

More PPSI (Pounds Per Square Inch)

That statement is how I have looked at it. Thats a little easier for a Mississippi boy to understand.
Down in the swamp, if you had skinny tires they would cut down to the harder ground, if you had wide tires they would float on top. In deep mud the skinnies work great as long as the mud isnt deeper than your tires are tall. Then you bottom everything out. Thats why we used to put big wide swampers on mud trucks.
I dont go mud slinging anymore and the terrain here in central/western NC is a combo of clay and granite, with occasional mud. So skinnier tires work out best here. I love the 10.50 width for small to midsize trucks. And for a bigger trucks I tend to go a little wider, 11.00-12.00.

 

[frumpy]

Big, fat tires are only for show trucks and tundra buggies.

I think thats a pretty ignorant statement (the show truck part). My last wheels I had on my YJ and grand cherokee were 33x13.5 and they worked awesome. When aired down they would go up or through anything. A wider tire works better in a lot of situations suck as limited traction when you need a wider footprint or soft terrain including mud or bogs.

The width of a tire really depends on the type of terrain and I know where I wheel right now a lot of the guys running skinnier tires have more problems due to the mud. They sink down more and land on their diffs whereas the guys running wider tires are more able to float on top of the mud or soft terrain.

 

[frumpy]

That statement is how I have looked at it. Thats a little easier for a Mississippi boy to understand.
Down in the swamp, if you had skinny tires they would cut down to the harder ground, if you had wide tires they would float on top. In deep mud the skinnies work great as long as the mud isnt deeper than your tires are tall. Then you bottom everything out. Thats why we used to put big wide swampers on mud trucks.
I dont go mud slinging anymore and the terrain here in central/western NC is a combo of clay and granite, with occasional mud. So skinnier tires work out best here. I love the 10.50 width for small to midsize trucks. And for a bigger trucks I tend to go a little wider, 11.00-12.00.

more ppsi isn't always better, I mentioned mud in my previous post (and as much as I hate it its always on the trails). But in wet rocks (either water falls or after rain) more ppsi will actually hurt you.

 

[scarysharkface]

A wider tire attracts more nails. :costumed-smiley-007

Skinny tires seems to find the solid bottom in mud and snow better than fat tires.

As has been stated, skinny tires just look better!

John