I have been laying around nonstop for a day or so after working 3 14 hour days so I kept on digging on this topic, I definantly did sound like a jerk dismissing the articles points. There is little info on the interwebs about how tires are engineered. There is some good info on how drag racers calculate their suspensions, tire sizes etc but that is simpler than what we do as the normal force and friction can be calculated with much more simplification on a flat surface. I think this below forum thread (read posts in the middle) offers some insights into how complex this engineering is.
http://www.ls1gto.com/forums/archive/index.php/t-282956.htmlSomething that gets into the zone of the complexity is here:
"However wider tires ARE better for lateral traction (cornering) because
of the SHAPE of the contact patch. A thin tire has a long narrow contact
patch and a wide tire has a short, wide contact patch.
And a longer contact patch is bad, because under high cornering forces,
the tire is pointing in a different direction from the direction of travel,
due to the slip angle (up to 5ish degrees, depending on the tire compound).
And a long, thin contact patch being dragged across the asphalt at a five degree
angle will lose traction at the trailing edge, because the rubber gets
dragged sideways a greater distance.
This effect is THE reason why wider tires are better for cornering."
I think its important to note that offroad the loading of our vehicles varies alot on inclines and irregular surfaces as the tire forms to the ground, so the standard normal force calculations for friction are going to always be on angles, and there is going to be a heck of a lot of lateral movement as we traverse obstacles. Sidewalls are flexed, tires contact patches are being pushed laterally shearing, flexing laterally etc. For digging into ice and mud, I see alot of real world experience to get a narrow tire to go deeper into the surface and a wider tire would tend to have some flotation effect. For rock crawling, just getting your tires ONTO something is key, like a solid purchase on a rock. hence wider tires just to find purchase, a simple insight. Width also helps you not roll over.
Utlimately a huge amount of your tire traction comes from your compound, how much of the tire is applied to the ground/rock/obstacle, and the tread, and then the angle you are loading the tires at, and then the torque you are applying as the tire has some shearing, often in multiple directions. It is clear that the contact patch of a taller tire or a wider tire is not that different, but we drive both taller and wider tires offroad for crawling.
I feel like this article is so simplified, its like I should say, drive a heavier truck offroad for better traction...the normal force will be higher, clearly that is not the case as a heavier truck has a lot of trouble sliding on slippery surfaces, moving up inclines, and will throw itself around on its suspension as it articulates with far more force, momentum etc... requiring even more traction to stay put on an obstacle.
The engineering of what we do is very very complex, as the suspension keeps the tires on the ground, the tire compounds, the exact penetration into the dirt, rock etc of the facets of the tire lugs and tread, its probably almost impossible to model and rather has to be done just be measuring the forces under diverse experimental conditions.
The author of the article is basically saying its cheaper for him to put taller tires on his truck due to the issues with lifting it to fit wider tires, to get a similar contact patch.
Topic: Blue Taco, Tire Logic.... wider vs taller? (Read 4799 times)
