You will get better overall handling from a 40 series tire than a 30 series in the same width unless maybe you are on a road that is as smooth as glass. Like stated above, the width of a tire makes a huge difference in the fatness of the sidewall. A 285/30 has a fatter/larger sidewall than a 225/30...you can easily tell by just looking at the two tires even though both are a 30 series tire.
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