Quote:
Originally Posted by Dubbedown
Correct, had 197s with 235/40 PS2's and I was rubbing on the outside on the fender liner, and the fender itself - caused slight warping. But I thought that was more of a height issue, and less about width. Thus, I thought a 35 profile would be ok...?
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it may have been a height issue then, but...
235/40r18 has an overall diameter of 25.40"
vs.
255/35r18 with diameter of 25.02"
= total RADIUS difference of - 0.19"
however...
235mm --> 9.25"
255mm --> 10.03"
= outer tire difference (1/2 of overall) of + 0.39"
so...
even if you're losing 0.19" in height (to center of wheel) you'll still gain 0.39" (outer clearance from centerline of wheel), and because the arc trajectory of the wheel does not change, the 255 will most likely have clearance issues on the liner.
side note: a 245/35r18 has a -0.33" RADIUS difference and a + 0.20" difference in width from the CENTERLINE, all vs. a 235/40r18.
my bet (purely based on the math) is a 245/35r18 will be the widest you can go without changing camber or suspension components on an 8.5" et42 (et40 really, since we're comparing to an 8.0" et34. the error here would be ~ 0.078", or 2mm / 25.4mm)