My ssr 18x8 with 235 tire are 46lb, by comparison the 98 car has 17x8 with 225 tire and they are 43lb. Keep in mind that it also depends where the weight is on the rim, some rims have thick spokes and thin outside others have thin spokes and thick outside. I think its better to have the heavier part of the rim closer to the hub. Also the 215/45 tire will give you better acceleration being smaller OD the stock. I went with 235/40/18 to keep my OD the same as OEM. When I swapped the 225/45 tire with 17s on my white car I noticed the car a little more responsive due to less weight (3lb) and lower OD. Also keep in mind that usually the higher the speed rating the heavier(or stiffer sidewall) the tire in the same size.