What is the largest wheel I can put under a stock C3 fender?  I'm pretty much being forced to complete a replacement frame for my '74 within the year, and in doing so I will be having a C4 suspension installed on the frame.  Originally I was going to be going with 17x9.5 front 17x11 rear ZR1 wheels, but I will not be able to afford the necessary bodywork on the fenders to fit those tires for at least a year or more.  I've read previously that the largest tire that could go on a stock C3 was a P255, as a P275 would clip the fenders.  But that's on a stock C3 suspension.  So my question is, what size wheel can I fit under there without replacing the fender or mini-tubbing?  As I understand it the 17x9.5 wheels are all a P275 size.  

Hey I want to do the same on my 68 I saw a few great lookin pics of a 71 silver here with 18s boyd cottyngton rims. I think 19s in the rear and 18s up front.After doing some measuring It looks like I can definatley fit 275's in there, maybe 285's. 9.5 to 10 inch wide rim not sure about offset though It looks like around +18mm in order to get the rear wheel further in and still clear inner fender. I saw a few rims with 13,15,20 and 25 offset on ebay. stearn was one of them. I've seen them in  5x120mm  and  5x4.75(120.65) They say they use the 5x120mm bolt on the 4.75 bolt with no prob's. Again I am not sure the exact offset I need yet but its close. If i cant get just what i want I will just use thin concentric spacers to adjust wheel position(which u can find on ebay also, they will custom make them). More positive offset will give u room to move wheel back out towards fender. My email livinlife63@yahoo.com    Pete I have stock suspension and wheel wells on my car. I have lowered suspension some using bolts in rear and cutting front springs to get hieght down.  discounttiredirect.com has wide selection of tire sizes, i'm looking at falkins they have widest selection and damn good prices. Let me know what you find out on your car. I am going to do more measuring to be sure i can get what i want in there with out modifying my car. YOU MAY NEED TO CUT EMERGENCY BRAKE LINE BRACKET AND WELD REPOSITION IT TO CLEAR WHEEL, ITS ON THE TRAILING ARM.  the bigger rims might even clear them too. Pete