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Originally Posted by MustangRoadRacer
close, but not entirely accurate.
the mechanical grip a tire has on tarmac(its traction, static friction) is not dependant on tire width, but the compound of the tire, the temperature of the two frictional surfaces(rubber and asphalt), the weight on the tire and that is it. if we have an effective contact patch of 1 square inch with 700 lbs of weight on it, it will have the same traction as 2 square inches of contact patch with that weight on it. why? because now the frictional surface is doubled, yet the weight pushing on the surface is cut in half. however, switching to a stickier tire(and most performance rubbers are) will usually yield better traction obviously, and mostly ppl upgrade when it comes to tires, so they feel more available traction from these upgrades.
threfore, decreasing pressure in an attempt to change the contact patch on the tire on the road is not an effective way of changing grip for more or less under/oversteer.
additionally, if a tire is wider, it might not offer any greater traction to a tire of the same compound and design, but narrower dimensions, but in the dry it WILL however offer a contact patch with a larger face. this allows the contact patch to be more consistent and stable in its traction, as now an uneventy or the like will disturn the larger contact patch less as it would with a smaller contact patch.
So if you want better steering you should adjust your suspension and not your tires
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Since this is back from the dead I will add my two cents for s&g’s.
The two primary mechanism for tire friction are adhesion and deformation. Adhesion is the natural “stickiness” of tires that allows the tires to adhere to the pavement on the molecular level. Deformation occurs as the rubber is distorted to follow the rough contour (microscopic) of the road. On dry pavement the total tire friction comes from both adhesion and deformation, while on wet surfaces deformation alone is responsible for tire friction.
The tire compound and temperature are important because they effect the amount of adhesion and/or deformation the tire is capable of generating. A softer tire compound is capable of deforming to the road irregularities better than a harder tire as well as exhibiting a higher net force on the contact path. While a cold tire may not be as sticky as warm a tire, an over-heated tire may be significantly harder than a cold or warm tire.
As load is placed on a tire the rubber is pushed onto the road causing it to fill in the microscopic irregularities that make up the asphalt. For some initial load the rubber will only partially fill the irregularities. As the load is increased the rubber will continue to fill the irregularities until the cavity is completely filled with rubber. After this point additional load results in mostly compression of the rubber and localized distortion of the contact patch.
As a result there is a particular load at which the effective coefficient of friction is maximum. At all other loads the effective coefficient of friction will be less. This phenomenon is referred to as tire load sensitivity. In most vehicle application (on asphalt) the tire is operating at a load above that of which gives the best coefficient of friction. So any decrease in load that can be achieve will result in better coefficient of friction performance.
Adjusting the tire pressure for a given load will change the contact patch area. An increase in tire pressure will reduce the contact patch area, and a reduction in internal tire pressure will increase the contact patch area. If the load on the tire is fixed and the contact patch size is varied the coefficient of friction is also a varied. If the contact patch area increases the load per unit area decreases and the effective coefficient of friction increases. If the contact patch area decreases in size then the load per unit area increases and the coefficient of friction decreases.
With the load on the tire fixed any change in coefficient of fiction results in a change in lateral force generated by the tire. Increase in coefficient of friction equates to an increase in lateral force (for a given slip angle) and vice versa. Adjusting the front and rear lateral forces with respect to each other allows the vehicles balance to be tuned via tire pressure.
Both under-inflating and over-inflating will resulting in uneven tire wear. Under-inflating will also increase tire temperatures. Heating of the tire occurs as the sidewall deforms above the contact patch. As the tire rotates a new section of side wall deforms and then is restored to its original shape and the cycle is repeated. Under-inflating the tire cause additional deformation in sidewall and therefore an increase in heat generation.
Excessive heating will greatly shorten the life of any tire, and can result in catastrophic failure of the tire. Over-inflating the tires reduces the tires resilience against bumps and curbs which also could cause premature failure of the tire. When tuning the tire pressures it is critical to adjust for the tires operating temperature. The internal pressure of the tire will increase as the tires temperature increases.