Yes I can. If you look at each infinitesimal point on the tire, a wider tire has LESS weight per point, than a narrow tire. Less tire area means more weight on each infinitesimal point.

If you calculate the frictional force at each point, it will be LESS for the wider tire, than for the narrow. Same u, because its the same tire, but different N.

I think we are arguing in circles. The competition rigs run the sizes they are given by the sponsors.

Its certainly possible that a wider tire gets better OVERALL traction than a narrow tire, because of the larger surface area. I've never said that wasn't possible. My argument is that pressure versus contact area is what we are arguing about.

 

Yes, interco does. TC ran those for a while. They were AWESOME offroad.

Problem is, they are just one step above a wooden square on the road. Flat spots, out of round, and louder than anything I've heard in a while.

 

but is simply defining friction, but not the full definition of friction coeffecient as an equation.

I agree I do enjoy these discussions and do learn from them.

 

Yes, but I just copied the post from wikipedia. I put the part in bold that I was referring to. I was pointing out the part about surface area applying to nanoscale applications, and not macro scale. That was all.

 

I looked at them but decided against Interco as their compounds don't do well for the road. Biased ply tire have a whole different set of potential problems over radials. One of the big goals of my rig has been to keep it streetible but also very offroad capible.

 

I didn't read everyting post so dont flame me or any thing but What Axle is saying is -Friction is distinct from traction. Surface area does not affect friction significantly because as contact area increases, force per unit area decreases. In traction, however, surface area is important.

For traction contact area is important. For force of friction it does not matter. Fof friction is equal to the normal force multiplied by the coefficient of friction. There is not area in the equation. An coefficient of friction is a dimensionless value. So the force to move an object depends only on the normal force and the coefficient of friction between surfaces.

It is important, due to broad application, to point out the specific case of multi-wheeled vehicles or vehicles with multiple contact patches between the tire and the road surface. Multiple wheels do not increase a vehicle's traction, because the friction force is independent of the contact area.[1] The friction force (Ff) is dependent upon the coefficient of friction (COF) between the contact surfaces and the normal force (N = a force perpendicular to the contact surface).

Ff= N(COF)

A greater number of wheels will allow a vehicle to carry a larger load, thus increasing the resulting normal force. More traction is achieved with a greater load because the potential frictional force has been increased.

The case of wheels sharing a given normal force is particularly important in vehicle design. Two identical tires sharing a common load achieve maximum stability when they share the load equally. Likewise, an unequally loaded pair of tires sharing a common load will not be able to achieve the same maximum stability.

The traction force is given by:

Traction Force = Driving Torque/Radius of Wheel.
Using conservation of energy, we are aware that F=ma and hence P=Fv or rate of work done. In order to calculate power:

PE = dTF / dt + dPL / dt
where Pe = Efficient Power, PL = Power Loss during mechanical conversion, and TF = Traction Force.

well anyways the rest is there for those who are interested

 

Well said

 

Well if we seperate friction from traction in trire than it seems this is a mute point. And simply going in a circle of I'm right your wrong. http://www.merriam-webster.com/dictionary/traction definiton #3a fits so dudes your soo right, in a paralell deminsion or something. So I think you equation would apply to railroad were the dimensional contact is constant and the surface area is as well on the contact of two constant surfaces, like a rail wheel on a steel rail.

I know my experereinces from rock climbing, mountain biking, motorcycles, and 4 wheeling. You can direct as much weight as you can muster on a small contact area and afterward sit on your butt wonder what went wrong. The same amount of force over a wider contact patch will leave you on the rock face, in the saddle and looking for the next obstacle. Though not true in every surface or terrain but for rock yeah.

If a wider footprint is less value than a single point of contact with great amount of force pushing it down than why on earth do we air down on trails?

Sai I really don't see where either were your coming from.

 

Again, you miss the point.

Again, I'm not sure why you don't understand.

No one is talking about narrow contact patch being better.

You are arguing that overall, more contact is better than more force per area. No one is contradicting you. We are talking about the differences in friciton, traction, pressure, and overall useability. You are the only one making a case for one being better than the other.

I dissagree solely on the point of practicality. My narrow tires don't rub. I'm not driving a comp rig. Therefore, narrower tires are better. If I could fit a wider tire, and I was convinced that I would get better traction with the wider tire, I'd run it. I can't, so I don't.

Where is the issue?

 

I don't know guy, I surely must be missing something. I surely didn't seem like that.

So ok.

I still say to the original post, enjoy.

I've got a set of 33/10.5/15 BFG A/Ts on factory toyota aluminum rims I'll sell for cheap.

 

i also learned alot form this post it is great reading!!

im going with the front lockright...
other than that the only other thing i might do is that steering recall... hopefully they dont mind me towing in my truck cause its offroad only

 

Please read it yet AGAIN. Coefficient of friction is SOLELY dependent on the two materials. Only in a few very special situations does area come into play - and those don't apply to us.

As AxleIke stated - 80% of the "offroad aftermarket" is fullsize domestic trucks (data courtesy of SEMA). The people who spend the majority of that money like the look of wide tires, so that's what sells. Since that's what sells, that's what sponsors give their rock-buggy competitors to advertise!

Wow - Mr. Apple, how do you compare to Mr. Orange? Different sizes, tread patterns, construction, compound ... think there might be a more logical answer to the difference in the behavior of the tires than contact patch size?

x2

 

I wasn't trying to be offensive.

Simply saying that I agree with your real world arguments, and that I was never contradicting you with respect to a wider area giving better traction. I was stating my point that a narrow tire has greater frictional force per unit area than a wide tire.

Your experiences say that more contact area trumps the greater force per area.

I can easily see how that would be the case.

 

1)You didn't read it or don't comprehend what you read. It even has a diagram example on a box on and incline.

2) I'm sure that you are right this is why there is competetion only tires. You don't see them on the fullsize rigs do you?

3)You might be right, but you might be wrong too.

4)oh a direct attack. Is this a defense mech to protect the ego?

Dude if it works for you great. But don't get bent out of shape when someone calls BS to your rationalizations. I can't wait till I can actually wheel Colorado maybe then I can accect an aurgument for fact but till then I'll not regurgitate a theory someone else wrote and hold it as the gospel of off roading tire technology. I'll stay with my expereinces and hold them as lessons learned

 

Well, this is approaching a pointless fight rather than good debate.

I'm not sure why you feel my post was an attack on you, but it wasn't. Sorry if it came off that way.

Apologies for the offense.

 

My explanation:
On a flat road a 33x12.5 tire is gonna have more traction than a 33x10.5 provided both are aired to the same pressure, both are the same tread pattern, same rubber compound etc. The equation is Ff=Coef*Fn, and the Fn for the wider tire would be greater because the tire itself is heavier. Coef between the two tires would be the same because contact patch and pressure per square unit cancel each other out.

On a rough road or on a trail, the advantage of the heavier wide tire would be negated by the smaller footprint of the narrow tire. The smaller footprint means the weight of the vehicle is concentrated on a smaller area. While this doesn't do anything for friction, it does mean the narrow tire will deform to contour with the rough terrain better than the wide tire, in effect giving it more surfaces to push off of, or better traction. This is why it is good to air down tires for wheeling, and to achieve the same level of traction, a wide tire will have to air down more than a narrow tire.

As for why rock crawlers run big fat tires, I'd say it's because they run beadlocks which allow them to air down almost as much as they want, plus they need as much contact patch as possible. Also, for those who run water in their tires to keep their CoG down low, a fatter tire has a larger volume=so more water can be put in their tires lower.

 

^This is more of an attempt to understand things myself, I realize everything I just posted was already said, but I needed to put it in my own words to make myself get it

 

 

You DO realize I'm an engineer and AxleIke is a scientist, right? That we have college degrees in this shtuff?

The box on an angle diagram is being used to show the normal force varies with angle - it has nothing to do with the contact area.

It's VERY easy to inject a competition tread compound into a mold you already have ... very expensive to make a mold just for the competition group.

Please read it again. Pay particular note to the chart showing the coefficients of friction for various materials and the lack of mention of area. Also the two sentences "However, the coefficient of friction is not a function of mass or volume; it depends only on the material. For instance, a large aluminum block has the same coefficient of friction as a small aluminum block."

Whether a tall/skinny tire works in CO and doesn't work in WA is not the point here - that may very well be the case. The point is that CONTACT AREA has NO effect on the fricional force, and since a skinny tire and a wide tire generate the same friction force, but the skinny tire generates more unit pressure and fits better for a given amount of lift, that GENERALLY the tall/skinny tire is a better choice for MOST of us.

and back on topic - since a 33x10.50 will fit with no lift, have the same ground clearance under the axles and less stress on the various components, I don't see any reason why you should lift a preTacoma IFS rig.

 

There are some reasons depending on your planned uses even if you still plan on using 33x10.5's (I'm talking mild lifts)