Help with tire clearance issues!

[2L8 ULUZ]

I need some advice. I have the mods listed below with five-lug cobra r's. I have no idea what offset the wheels are. Up front I am running 245/40 and 255/40 in back. The problem is that my right rear tire extends past the fender well and is being ripped apart every time I hit a decent bump at speed. The left rear is noticeably further in but still makes contact on very hard bumps or a very big load, as do they front tires. What tire can I go with in back to get rid of this? Does the difference between a 40 and 50 series tire relate to the width at all, or just sidewall height?Would a 245/50 work? Help! Any input is appreciated.


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90 LX Convert - Griggs GR-40 Street Kit, GT-40 Irons, Cobra Intake and MAF, Auburn 3:55, Full Frames and 8 point cage, 5 lug. Stiff and Strong, like a camp counselor.