I think they should be called "wheel donuts." Everything shaped vaguely like a donut should be called a donut. From now on, o-rings, spigot rings / hubcentric rings, piston rings and c-clips shall all be known as donuts. The only toroid not to be called a "donut" will be donuts themselves, which shall be henceforth known as cake rings. I don't care what confusion it causes.
Oh yeah. Tires/tyres are donuts, too.