Another tire width discussion? I'll keep it short.
After my own heated debate on this topic years ago with Ken I really did my research. The most simple way to state why wider is better for road racing, is like this. Lay a typical papermate 55x23x13 mm eraser on a dry table top. Is it harder to push it width wise or length wise across the surface? It is far more difficult along its length. Conclusion- contact patch shape counts, a lot. Even on a P2 prototype race car their foot-print under maximum load is about the size of a mens size 11 sneaker, so all these little details and dynamic interactions matter to a great extent.
Stuntman, it is rather inaccurate to assume that as the section width or tread width increases linearly that the contact patch area also increases linearly in this relationship. I feel that point is at the heart of your argument with Ken and to that end he is mostly correct in this instance. Conceivably, in fact it could decrease depending on the relative vertical stiffnesses. What will change is the shape of the contact patch, becoming shorter in the longitudinal direction as it is made wider (assuming a constant load), and this may be partly responsible for more uniform unit loading over the area of the contact patch.
Likewise, Ken, I also have come to disagree that the contact patch area remains constant as [Vertical Force] / [Constant Inflation Pressure] suggests or that tire rack's article is entirely comprehensive. I'd argue that under load, many more technical variables come into play that are highly significant to this debate, a minor point I would hope we could at least agree on.
As it turns out, the physics in actual use are far more complex because in the real-world as the car isn't sitting on a glass floor at tirerack, it is on a race track with many other variables at play. I do agree with you that contact patch area is primarily load/inflation pressure driven, however,
I have come to learn that the sidewall stiffness of the tire (variable) does carry a portion of the load and that portion can also vary with inflation pressure (variable).. so there is no one simple answer which is what I think many seem to want or expect in this space.
The consensus among many engineers seems to be that all tires have a load sensitivity curve (variable) and this curve is based on a combination of construction, aspect ratio, and sidewall curvature (either as molded and as mounted on a rim) and the curve is not linear- so again there is no simple division equation to express this relationship- it gets more complicated.
The best wording I have found online to best describe this affect in the real world, is that it is entirely possible to have tire "A" provide better "grip" up to a certain point of speed around a curve but tire "B" to be better at the upper ranges of cornering. Tire Engineers and race teams also have to decide if it is better to have a flatter response curve with a more predictable response or one with higher max grip but only over a very narrow cornering angle that can break away with little warning at the slip angle approaches it's max threshold. Hence, the science of modern F1 tire tech and per track, weather, and other compound/sizing optimizations.
Tire construction and the carcass design, thermal distribution also are significant as it relates to the contact patch shape with wider tires having definitive advantages to a point. This year I got to reap this benefit in use, by seeing better loading and heat distribution to the point whereas my wear dropped off.
All else equal, most any race tire techs will tell you that integrating more uniform unit load and associated grip coefficient function over the entire contact patch should make available more total lateral mechanical grip. The wider tire probably also has higher vertical and lateral spring rates, meaning less camber loss and lateral distortion in actual driving respectively.
I like to provide references. If you want the unfiltered revision to this debate... go here as even the top tire engineers duke it out you I'm sure you will find their credentials in order:
http://www.eng-tips.com/viewthread.cfm?qid=102250&page=1
One of the members which explained it to me in great detail years back is a frequent poster to the forum, and has been a tire engineer for almost 40 years.
Other good general references can be found here:
http://www.carbibles.com/tyre_bible.html
http://www.turnfast.com/tech_handling/handling_pressure4.shtml
All I can offer is that these aren't necessarily easy technical concepts to grasp, and good argument and debate never hurt anyone so take it easy.
Best Regards,
John
Actually, I slathered the bottom of the tire in water-based paint and then lowered the car on the contact paper. So that was a static measurement and not a dynamic one which would change area shape as well.
