New, rubber UCA bushings creaking

Hello gents:

I just installed a set of Moog offset upper control arm bushings on the right control arm of my '69 Valiant today; I did the left side yesterday.

The left side was just fine when I put it together, but the right side creaked, and continues to do so. It's not as bad as when I first put it in, but it's still creaking, and noisily too.

Any reason for this?

-Kurt