[aerohead]

My opinion is that while "narrowness" appears to be a condition of LLR tires,it is not a governing parameter.On the second page of the sticky,I briefly addressed MPG as a function of rolling resistance.And perhaps rolling resistance should be the guiding parameter,however it is achieved.--------------------------------------------- The ultra-low rolling resistance tires on Ultralite and PNGV cars by GM were narrow in comparison to "performance" tires.They were also high-pressure(65-psi),cast-elliptic sidewall,low aspect ratio,on larger(18-inch) wheels,to provide a large circumference,with reduced cyclic deflections,and very careful combination of both high and low hysteresis rubbers,to take advantage of those attributes,where they would do the most good.The aspect ratio was compromised to maintain a given air volume without going to a heavier,wider tread ( which would also aggravate polar moment of inertia).Tread block design was also a key to LRR,with many transverse hinges,while controlling noise propagation to meet stringent EPA noise criteria.---------------------------- One ancillary consideration for the "narrow" profile was to enhance the frontal area capabilities of the cars,reducing drag via a "bolt-on" modification.