Yep ironX will chomp through it though if they are heavily contaminated then I'd suggest getting the top layers of crap off with your usual wheel cleaner and get as much as you can off then rinse,inspect and apply ironX to the effected areas and allow to dwell for 5/10 mins agitate if needed,rinse and inspect again, if they are really really crapped up it might take a few goes before you see improvement. IronX paste is good for longer dwell time as its thicker than the spray version so may be worth considering if its needed.