Post by
SmithSR »
https://forums.nicoclub.com/smithsr-u5241.html
Thu Nov 24, 2005 12:57 pm
Don't overlook aspect ratio because only the full equation will lead you to the answers you need.
And even then, Different tire manufacturers use different yardsticks to measure their tires.225/45-17 from Yokohama to Falken to Toyo will have different casing and sidewall thickness, different tread depths, different overall diameters, different section widths.They will usually be close but we deal sometimes with such a minute margin for error that the answer will always be to mount one up and see what you think.
IMO, you should disregard 7" altogether.
You should make the goal to keep overall diameter as close to oem as possible. Any taller and you lose gearing, response.
8" 215/45-17 for the slightest of stretch. Not really even stretched.
9" 225/45-17 has stretch. 245/40-17 is ideal for fitment (very slight angle on stretch) and ideal overall diameter, but isn't available in a ton of brands.255/40-17 is getting to be too tall. diameters range from 25" to 25.20" both of which are above oem OD.But on the 9" with 255/40-17 you get a square shoulder. The trick is, this doen't fit for **** under the back of an s13 unless you start to roll fender.
The only problem with a perfectly square tire/wheel is it becomes harder to tuck and harder to clear the coilover spring perch. Sometimes to get a solid fitment, you need that sightest bit of stretch, like the 215/45-17 on 8" or 225/40 on 8.5" etc