I am selling the "bottle cap" center caps off my Type-C's. Two of the caps came off, the 3rd I had to hit it quite a few times to get off. The fourth cap is on real good. I hit it a few times, but do not want to risk damaging it from hitting it, like I did with the 3rd one. It has a rubber ring around the cap. Any advice?

 

Try stuffing some towels in the back and use the handle of a hammer to knock it out? Don't know if that will damage the cap though. Proceed with caution haha

 

They bend very easily. You can maybe try spraying soapy water or some form of lubricant that is safe for rubber (pb blaster is probably too strong) around the inside and outside of the seal area and then put something in the cap to distribute the impact and give it a couple light taps. I have a plastic/rubber hammer with a wooden handle that I stick in the cap and lightly tap it with another hammer.

 

rubber mallet is the safest way