chrome has flaked off or pitted on the rim, strip them down you'll find it a lot easier to clean/polish them properly plus you can do the spokes and the awkward bits on the hubs at the same time
steel or alloy rims? it's not clear in the pic but they look like steel rims ?
couple of options
1 re chrome the rims, expensive and not many chromers will even attempt them if they're alloy, if they're steel you should be ok
2 polish , mechanical is best ie on a buffer , cut the flakes with sisal mop and cutting paste to get them smooth then go through the grades of polish in turn to blend the rim with the remaining chrome
you can get mops that fit electric drills , if you don't have a bench machine , these will also help with the following
3 hand polish , will do it, it will just take longer, again, you need to smooth out or blend in the edges of the chrome where it has flaked start with Autosol and good quality polishing cloths , to get the flaking smooth then use Peek or similar to polish , lots of elbow grease , and time, lots of time
, although it can be very therapeutic
stainless steel pan scrubbers are good to , the ones made from curly swarf, to get the rust off steel / chrome ,will scratch alloy though, a lot better than tin foil and wont leave any bits stuck under the edge of the flaky chrome
