I am planning to replace the stock steel rims with alloy ones on my recently acquired Raleigh Twenty. It currently has 406 (20x1.75) rims. Is it best to stick with this size or is there any benefit to converting to 451 (20 x 1 3/8) rims? I know that the brake calipers would have to be changed. I am thinking of using Sun-Ringle CR-18 rims but would consider others.