I use WD-40 to clean roofing tar off my tools so that might work on road tar. I also have an old can of Turtle Wax Tar and Gum remover for my autos. It's the old stuff in a metal can, not the plastic spray bottle.
Is that a chromed steel rim? It kinda looks like aluminum alloy. If so, best way to clean is with Scotch-Bright sponge and detergent. The spots in the photo may not come out completely, but you'll probably be able to fade them some.
3M General Purpose Adhesive Remover - part # 08984. I bought an 84 Buick Riviera convertible from a guy who was selling it because he couldnt afford to have it repainted. It had set under a large pine tree and was covered with sap. It took me two cans of the adhesive remover and a bundle of rags but the sap came off and the paint was fine. (Did have to put a new top on it though.) Given a little time and attention it will literally melt road tar without damaging the paint underneath it. Once you have a can of it in your garage, you'll wonder how you got along without it.