dont worry about offset, lots of people on this board i have noticed hear the word and freak out not knowing what it means, but i you are buying wheels, the shop that sells them to you will send you the correct measurements, and if they dont, you dont need to buy from them. with 18s, get either a 225/40 or 215/40. some get 225/35s but thats pushing it with a car that weighs as much as ours do. so far i have had no problems with my 35s though. as for tire brand...i owned a set of pirelli p7000s whcih were really good for the short while i had them, but i have owned two sets of Nitto NT555's. the first were 225/40/ZR18s which presented rubbing problems in the rear but it only cost me $20 to get the fenders cut. the set i have now are 225/35/ZR19s and the small sidewalls have not caused any problems yet. just keep the tire pressure good on any set you get. other tires that i haev heard are good but i havent owned: all Toyo, Nitto, and Pirelli are a given. the Yokohama A520s are good as well as the Falkens. with a rim 18" or more i would suggest sticking to high performance tires and stay away from big name manufacturers like michelin, goodyear, and obviously, firestone. nothin wrong with those brands (excepting firestone, hehe) but nitto and yokohama base their profits on selling larger tire sizes.
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1995 Eclipse GS - HRC Stage 2 - Retired.
2004 350z Enthusiast / 2008 Nissan Versa SL