Last one to post in this thread wins!

My wife drives a cobalt, factory mag, we have about 3.5 miles gravel to travel to hwy. front wheels not bad brake calliper is close enough to wheel to keep it clean. Car was shaking a bit so decided to clean rear wheels. 15 freaking pounds of road dirt stuck inside the 2 of them. Going to try and devise some sort of scraper like the calliper does for the front. Or does anyone know of one I could buy?