With Solvol Autosol/Brasso and fine steel wool. DO NOT use a nylon pad or abrasives, this will damage the chrome. Steel wool however is softer than chrome so you will not touch the chrome, just the rust. NB if it's not too bad a cotton rag and polish will do it, but it's slower.
Classic car/bike enthusiasts have been doing this for years. :-)
Don't try this on ally rims BTW. Actually you can, I have, but it only ever gives a dull shine. OK if you like a dull shine...
Or do what i did...go stealthy
Rubbed them down (the chrome rims) and sprayed them black.
Raleigh Medale flatbar donated by a friend, ideal for my son to commute, but its was a bit err...not very cool looking for him. So i stealthed it up...looks quite good, the black hides a multitude of scabbiness on the rims. He's well pleased with it.