From my experience new glue does generally stick to the glue build up better than to the aluminum rim. Most people do not know it but one of the problems sew up rims commonly have is that the glue does not stick really well to the left over buffing fluid used from when the rim was buffed out. My favorite glue removal method is to dawn safety glasses, take the wheel out in the yard and use a wire wheel attached to an electric drill and watch the dried up old glue fly off.