Road tar comes from newly paved or resurfaced asphalt roads. This gooey product is sticky and will adhere to virtually anything, tires included. While it will do no real harm to the tire itself, tar globs are unsightly and cover up raised lettering. If inadvertently touched, tar will transfer easily to clothing or skin and may be nearly impossible to remove fully. In that case, it is far better to remove tar from tires than to deal with it once it makes its way onto skin or clothing.
Pour paint thinner on a rag and wipe it over the tar. The white spirit in paint thinner will immediately begin to dissolve the tar and your rag will be covered with blackened tar streaks. This works well for smaller patches.
Dip a hobby brush into paint thinner and scrub off large tar balls on your tires. You may have to dip and scrub several times before the entire tar ball dissolves and can be fully removed.
Wipe off any remaining tar streaks when brushing has been completed, using a rag.
Wear nitrile rubber gloves. These are resistant to solvents and thinners and will protect your hands from contact. In the absence of paint thinner, virtually any type of petroleum or a petroleum distillate product will work. Petroleum-based spray lubricants will act like a cleaner on tar. Kerosene and diesel fuel also are effective.
Never use gasoline to remove tar on tires. Although it will work, the flammability factor is not worth the risk.