My son's old Razor wheels were practically square - definitely time to replace.  My son is thrilled with the new wheels and a couple months later they are still working great.  Replacement was a little tricky - I normally can do those things myself, but had to enlist my husband's help.  It was also somewhat annoying that you needed 2 hex wrenches of the same size - we only have one set so had to find someone else to lend one.