[powerbench]

I think i'am reading your post right , but here it goes.The sizing you are doing is for your rims (17x9) ? I find (and this is just me ) usually , in your case you probably have a seven inch rim on those tires now..15x7. I have eight inch rims on my wifes 88, it has 275/40/17 on the back. Now i don't know the width of the tire, but in you tire calculator i bet it's close to 11 inches wide. Most of the time , you(or in my case me) would choose a rim smaller in width than the width of the tire. As far as for height or profile , it will depend on the tire , i know with our 17 wheels finding say a 50 series tire is harder than say a 40. Now 18 or say 20 inch rims have a bigger selection of profiles and widths. And to recap...and man i hope i'am remebering this right,in your case 235= width /75= % of 235 for sidewall profile/15=rim size...