Nope, you nailed it, Eric. Though bumpers are typically solid rubber... not just rubber coated. Olympic lifters use them so they can drop weights.

Now, you can drop a bundle of cash on bumpers (I believe that I have spent well over $400 on 2x45, 2x35, 4x25, 2x10 bumpers), or if you are looking to just beat around with something you can drop (axle cleans, let's say) then you can use car tires. It requires a manufactured flange of some type so it will adapt to a normal Olympic bar, but they work well and are pretty heavy. I wanted them for farmers walks or axle cleans. I could drop either without crapping up my iron weights in a parking lot. I only use my bumpers in my garage on a lifting platform... too expensive to scuff to hell on blacktop, but it saves a lot of energy to just drop a jerk rather than trying to lower it under control. Or, if you miss a snatch, then you don't have to sweat whether you just screwed up your floor. And it flat out feels awesome to lift with bumpers because they are so big. A 25kg (55lb) bumper is about as thick as 4 normal 45lb plates