18" mounty rim's on '06 explor

So i picked up a set (4) of 18" 8 spoke (fan design) '06-'07 merc mounty rims w/tire's for a very good price, dismounted the worst tire and found they still have the tpms sensor's in them (yes!bonus!), but my concern is just the rim it self weigh's 33lb's that seem like alot, does any one know what a stock 18" steel wheel weighs? I would like to know what effect does a heavy'er wheel have?, compared to a lighter wheel? Breaking, performance, mpg's? I'm not against selling the mounty rim's and buying a set of 18' steelies (i like the look), as that was my original plan till i found the mounty rim's for cheap. These would be for summer only as i will use the stock 16' ex rim's in winter.. Thank's

 

[Thunderace]

Ok i weigh'd rims and tire's ; 18" mounty 8-spoke rim w/tire =63 lbs
16" explor 6 spoke rim w/tire=50lbs
16" stock explor steel rim w/tire=55lbs
does anybody have a weight (or can weigh for me) a stock 18" steelie w/tire?
Any help would be great! Thanks