I think what he's saying is Advans at 205/55 *could* outhandle Toyo T1-R at 225/45. And I seriously doubt that is consistently repeatable with the larger (more flex-susceptible) sidewall
Of course, if he means 205/55 will always outhandle 225/45 of any given kind of tire, he's high
Oh, btw - even IF he were right on the first one - I *only* want 225/45 or even 215/45 or 215/50 - not 205/55.
As far as rotational diameter goes, all these sizes are close enough to be just fine - in fact, even on my 16s, I run 215/55
O.K.: Let us assume
that a 205/55 tire has a section width of exactly 205mm and an aspect ratio of exactly 55 percent. (Actually, it has a section width anywhere between 200mm and 210mm and an aspect ratio anywhere between 52.5 percent and 57.5 percent. See the sidebar below.) Let us also assume
that a 225/45 tire has a section width of exactly 225mm and an aspect ratio of exactly 45 percent. Then the length of the sidewall of a 205/55 tire is 205 x 0.55 = 112.75mm, and the length of the sidewall of a 225/45 tire is 225 x 0.45 = 101.25mm. In that case, the difference in length between the sidewalls is 11.5mm, or 9/20th inch, not that much a difference in the greater scheme of things. However, on a 7" rim, the sidewall of the 225/45 tire will be cinched in like this: \ /, whereas the sidewall of the 205/55 will be closer to straight up-and-down, like this: ||. The 205 is more likely to handle in a symmetrical manner in response to lateral forces than the 225/45 will (on the 7" rims) for that reason alone. The concept is explained, in somewhat different terms, at this link
As to flex susceptibility, many other factors than length enter in. Most high performance tires -- including the Yokohama ADVAN Sport -- have inserts in the sidewalls to fine-tune the flex. A "touring" tire with an identical sidewall length to an ultra-high performance tire will, mounted on the same rims, have more flex, in order to give a softer ride. The technology is in place to give a tire whatever flex is appropriate, more or less without regard to the sidewall length (within reasonable parameters, of course). As you undoubtedly know from your experience with the Toyo T1-S, they give an outstanding ride and good road roughness absorption, at the (acceptable to many) cost of a little vagueness in steering precision -- at least that was my
experience with those tires in the 225/55R16 size. However, that size is one of the sizes in which Toyo employed polyester as the body (carcass) plies. Perhaps the sizes in which Toyo used rayon for the carcass material handled more precisely.
The fact is, among tires that fit on a 7" rim, a 45 aspect ratio is too short for any tire that has an adequate load index for a Mazda6. If you want a 225 section width on a 7" rim, you should go wth a 225/50. Or, if you want a 225/45, you really should be looking at a 7.5" rim. (The 215/45, if you could find one, would bee too small, and effectively would alter your gear ratios.)
The contact patch of a 205/55R17 tire inflated to 35 psi will be the same size as the contact patch of a 225/45R17 tire inflated to 35 psi -- the same amount of "rubber on the road" -- but the shapes of the respective contact patches will be different. The 45-series tire will be more susceptible to outside inputs (from the steering wheel or from irregularities in the pavement) to effect a change in direction, compared to the 55-series tire. Conversely, compared to a 225/45, a 205/55 will have more of a gyroscopic action ("wanting" to stay pointed in the direction they are rotating) than the 225/45 will, and will tend to track better. That will make the steering of the 205/55 a bit less "twitchy," thus requiring fewer micro steering corrections, than the 225/45 when traveling down a straight road, all other factors being equal.
SIDEBAR: as to the precision of a specific size designation, let us compare two 205/55R17 ultra high performance tires, the Michelin Pilot Sport PS2 and the Continental ContiSportContact 2. According to the respective manufacturers' data sheets, the 205/55R17 Continental will get 844 revolutions per mile, and the 205/55R17 Michelin will get 803 revolutions per mile, which indicates a 5.1 percent difference in overall diameter of the respective mounted tires. Plug that
into your on-line tire size calculators.