If you are further interested in this topic I suggest you pick up some basic literature on vehicle dynamics or google cornering stiffness.
The sidewall flex that everyone else is talking about is parameterized by cornering stiffness in the tire world. What it describes is the rate at which the tire will produce lateral force. Physically this can be seen as the initial linear slope of slip angle vs. lateral force for a given tire. Many factors affect cornering stiffness and the "stretch" or angle of the sidewall is an important factor. In testing the cornering stiffness will continue to increase until the angle of the sidewall approaches that of the tread section.
Construction of the tire itself will contribute to the cornering stiffness and things like tread compound actually play a much more important roll than the sidewall stiffness. It's easy to understand as sidewall flex but this is just one part of the interaction. For instance the relaxation time of each material included in the tire will have an effect. The stiffness of the summit in bending and in shear will have a large effect. Even the size of the bead mounted to the rim will have an effect.
As everyone has stated before some "stretch" may be good. In fact ALMS teams use it as a balance and tuning parameter. Take a look at the Pratt & Miller C6R's they usually run a wheel larger than the measuring wheel up front.
At the control end for the driver it's down to the required response of the vehicle. A vehicle with higher cornering stiffness will respond faster to input but will also drop off quicker at the limit (unless this is countered by material choices). Actually changes in mechanical grip are negligible unless extreme differences in cornering stiffness are had.
In the case of every street tire it will most likely be perceived that handling has been improved with higher cornering stiffness (especially by gear-heads). Until you run the risk of unseating the tire or scrubing your wheels handling will improve with stretch (as others have stated before comfort will not).
As with anything you can have too much of a good thing...
The sidewall flex that everyone else is talking about is parameterized by cornering stiffness in the tire world. What it describes is the rate at which the tire will produce lateral force. Physically this can be seen as the initial linear slope of slip angle vs. lateral force for a given tire. Many factors affect cornering stiffness and the "stretch" or angle of the sidewall is an important factor. In testing the cornering stiffness will continue to increase until the angle of the sidewall approaches that of the tread section.
Construction of the tire itself will contribute to the cornering stiffness and things like tread compound actually play a much more important roll than the sidewall stiffness. It's easy to understand as sidewall flex but this is just one part of the interaction. For instance the relaxation time of each material included in the tire will have an effect. The stiffness of the summit in bending and in shear will have a large effect. Even the size of the bead mounted to the rim will have an effect.
As everyone has stated before some "stretch" may be good. In fact ALMS teams use it as a balance and tuning parameter. Take a look at the Pratt & Miller C6R's they usually run a wheel larger than the measuring wheel up front.
At the control end for the driver it's down to the required response of the vehicle. A vehicle with higher cornering stiffness will respond faster to input but will also drop off quicker at the limit (unless this is countered by material choices). Actually changes in mechanical grip are negligible unless extreme differences in cornering stiffness are had.
In the case of every street tire it will most likely be perceived that handling has been improved with higher cornering stiffness (especially by gear-heads). Until you run the risk of unseating the tire or scrubing your wheels handling will improve with stretch (as others have stated before comfort will not).
As with anything you can have too much of a good thing...
Comment