Tyre Inflation Pressure vs Handling

Reducing tire pressure tends to make a tire cup, thereby actually reducing tire contact with the road. Maximum tire/road contact is achieved with proper inflation/load ratio.

Cupping is less of a problem with radial tires than with bias-ply tires, but both will also suffer more tread roll-over onto the sidewalls when cornering as the pressure goes down. This is why tire load carrying capacity is proportional to the tire pressure. More air = less roll-over = more load capacity.

Harvard wrote:
This is just a theory:

When the pressure in a tyre is reduced the contact patch is enlarged. The total dynamics of the rolling tyre start where the “rubber hits the road”. As such one half of the increase in the contact patch length is added to the mechanical trail there by increasing the straight line stability in the same manner as increasing the caster angle.

(Mechanical Trail is the moment arm between the steering pivot point (fore) and the center of the contact patch (aft))

"Dynamics" is the key word. When a tire is improperly inflated, the loads on the contact area change excessively causing unwanted scrubbing wear. That can show up as cupping wear as previously mentioned. It can also cause excessive linear wear on the outer edges of the contact area or any combination of other wear issues depending on how low the pressure is. Low tire pressure causes the inner portion of the tread (center) to carry less load than the outer portion of the tread. Tire wear is a very complex issue. I suggest you contact the engineers at Goodyear, Michelin, or any other major tire manufacturer if you want to learn more about it.

Or join and post your theories at www.eng-tips.com in the Automotive Engineers section. (no affiliation)

Chum lee

Tires inflated BELOW specification have a lot of sidewall flex as they roll. Flex = heat. Heat = short life.

The fact that tire is spelled tyre makes me suspicious of the theory. :)

azdryheat wrote:
The fact that tire is spelled tyre makes me suspicious of the theory. :)

I too tire of this tyre talk. :B