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      07-24-2005, 09:25 AM   #8
stressdoc
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Pondermatic provides the data (thanks!): 27 lbs. runflat vs. 24 lbs regular, i.e., 3 lbs. difference. That is within the range of variation of regular tires. 3 lbs. will not affect ride quality in most circumstances. Unsprung weight is important for handling over rough surfaces, that is, situations in which the wheel assembly is moving up and down. The lighter the wheel assembly, the easier it is to control the movement, it has less momentum. This is especially important for off-road motorcycles, desert racing, rallye cars and the like. It is not as big a deal for luxury cars on the street. I guarantee Cadillacs have more unsprung weight than an E90. It is the sidewall stiffness, as Pondermatic states, that is the relevant variable affecting ride quality, i.e., the extent to which we can 'feel' bumps. If you want a smoother ride, get higher aspect tires (e.g., switch to a 60 series) that are designed for ride quality. The tradoff is that the tire will 'bend' more during sideways loads, hence will not corner as well. I prefer the go-kart feel. When we are down to 30 aspect ratio tires, the difference btw a regular and a non-flat is almost imperceptible. At this point we need to assess which tire performs. Anyone know of any good runflat comparison tests yet?