Most aluminum alloy parts on bikes are clear anodized, which gives them a satin, not mirror finish. This coating is a lot harder than bare aluminum and will not polish up any shinier unless you power buff it long and hard. After that you will have to polish it over and over again periodically if you want to keep that mirror finish. Your choice; leave it alone or polish it forever. The only time I would polish aluminum is if it was never anodized or is really corroded and scratched up.