Total Lateral Load Transfer Distribution

[Sleeper68]

I've been quietly following this thread for a while and appreciate the excellent mix of technical and hands-on discussion. Your first statement has me scratching my head, not because I have a different opinion, just want to understand it. On the dunning-Kruger map, I'm at the peak of Mt. Stupid in terms of the contact patch, and how even and uneven loading can affect traction, as well as how friction is non-linear with load(I know enough to get most of it wrong lol). Any thoughts you guys could share might help me on my descent from that glorious mountain lol.

I'm no psychologist, but based on the fact you have the understanding that your knowledge of a particular subject could be better, I imagine you are not overestimating your ability. That being said, I think we can all learn something from each other. The best explanations I have gotten regarding tire dynamics at a basic level came from the book Tune to Win by Carroll Smith. You should read it; the entire thing. KYLE.ENGINEERS on YouTube also has a few videos on general tire frictional coefficient effects as a function of normal force and "slip" angle. Obviously this neglects the added variable of dynamic camber angle. He also worked for Mercedes F1 for a couple of years.

Since we are but lowly consumers, and do not own race teams, we are generally relegated to our own tire testing to obtain good tire data. Different tires like different dynamic camber angles for different loading situations (slip angle and normal force). I am switching to a new tire this year, RT660 from the BFG Rival S 1.5, so I will be performing my own tire testing to see what the Falkens like. Like iadr said, the tire likes what the tire likes. The best set of loading conditions for your car are what net the greatest average cornering forces on the same day, with the same conditions, on the same surface. Now, this ALSO neglects other considerations such as longitudinal tire forces (acceleration and braking) and any combo of the former on transverse or "cornering" forces. It has been my experience that more negative dynamic camber angle improves transverse but hurts longitudinal tire characteristics. Since most of us have solid rear axles, we can mainly concern ourselves with the front end in terms of alignments settings. I will be going to a test and tune next week before my first event to get a feel for the 660s on the surface I normally run on throughout the year. I will report back with my findings. SO far my experience with the 660 is it is less forgiving than the rivals, but is far better at communicating its status. Additionally, the 660s respond much better at lower temperatures and they heat up faster, good for a single driver like me. I imagine this will translate to a shorter tire life, but my rivals lasted about 2 seasons so I am ok with that.

It's a particularly/typically ugly application of academe against the human intellect, and should be left in the corrupt sewers it came from.

Yes.

So in action, whatever keeps the tread surface making generally the most effective contact with the road, is good.

I agree.

Empirical discovery shows there is actual bonding taking place, some say molecular or materials bonding. That means every millimeter squared of contact patch is better.

I would expand this to say that the every bit of additional contact patch with a significant pressure acting over its area matters. Distortion of the contact patch and its associated pressure gradient against the road or "pneumatic trail" is very important and is the ultimate output of all tire loading inputs. The resultant tire force is dependent entirely on the contact area, its pressure gradient with the resultant force acting at the contact patch center of pressure, the dynamic frictional coefficient at that time, and the force of the car acting on the tire. All of the input factors that lead to the resultant tire force and pneumatic trail are complexly tied together, and again, are generally characterized empirically as iadr said, especially in our case. One can educate himself on general trends for radial tires, but getting hard numbers from models is virtually impossible for laymen such as myself. It should also be noted that a tire will give you back whatever force to command of it up until it starts to "slip". I do not mean slip angle, what I mean by that is the tire will create a frictional force equal that of its portion of the force the car exerts on it to keep the car on a prescribed arc until its available frictional coefficient starts to fall off. Most tires follow curves similar to the one I have attached. Tires described as "peaky" usually have a friction peak that is taller but narrower and thus are harder to drive at the limit but are theoretically faster. This is represented by the blue line. Tires described as "forgiving" usually have a friction peak that is lower but wider and thus are easier to drive at the limit. This would be represented by the green or red line. The picture is not the best example, but you get the idea.

The center of pressure of the contact patch is generally behind the unloaded tire center if positive castor is present. This trailing effect is what generates self-alignment torque, which is what you feel in the wheel with your hand and is the torque that straightens the tires when you take your hands off the steering wheel. It is also the torque that falls away as the tire starts to become unloaded and starts slipping. This phenomenon is the basis of "feel" in the wheel and is one way experienced drivers stay on the limit of adhesion of the tires.

Suffice to say, the best way to educate oneself on tire dynamics, in my opinion, is to read books devoted to the subject. Specifically those books written by experienced race team members, drivers, or engineers such a Carroll Smith.