I used this "Hot Rims Chrome Wheel cleaner" from Meguiars and I was really blown away at how good it worked. Clay Bar's are always good too but this stuff was exceptional. They use Mag Chloride on our roads in Colorado and that stuff just won't come off of chrome. I used this stuff and let it sit and it seriously worked magic.
I also used it on the billet bowtie on my Avalanche and it looked brand new even after 4 years of road grime and no scrubbing to it.
I have never had ANY luck with any wheel cleaner ever and for some reason I picked this stuff up and now I tell everyone about it because it really worked for me.
http://www.meguiars.com/?wheel-care/Hot-Rims-Chrome-Wheel-Cleaner