Ph4tty

I think the sled adds a lot of contact pressure

I'm sure Pourin can set us straight

HOHN

Well, if it's contact pressure theory, I'm willing to take a stab at it.

Everyone here knows I've never let a lack of knowledge keep me from theorizing

Friction essentially has two elements: the coefficient of friction and the normal force. Notice there's no factor of of surface area, because it doesn't technically matter.

Surface area in this case is contact patch size. Any increase in surface area which would increase friction for a given coefficient is offset by the fact that pressure decreases at the same rate. In other words, they cancel each other out, and all that matters is weight.

So that eliminates tire size as a variable. Tall, wide, skinny, short-- it doesn't matter.

What DOES matter is the coefficient of friction. This is your tread aggressiveness. But this is also your track conditions.

On pavement, we are only concerned with the coefficient of friction between the tire and the pavement, because the pavement won't move.

But on a dirt or gravel track, it's both the friction of the tire with the stuff underneath it, as well as the friction of the stuff underneath the tire with the whatever ultimately won't move.

Imagine you're on a pulling track of nothing but ball bearings. You'd have good traction on each individual bearing with your tires, but the bearings have no traction on the road underneath, hence you have no traction either.

It's one of those things where the "chain is only as strong as the weakest link" and there's a chain of contacting surfaces between the tires and the immovable earth.

This is where tire size and such becomes a variable again if it affects what surface the tire will run on.


JMO

displacedtexan

Good point. I didn't think of there not being a lack of contact pressure in a pulling situiation. Did I word that confusingly enough?

Well Pourin? I got the post from Justin I wanted, now for the voice of experience