WD-40 is a petroleum distillate may just be kerosene or some thing along those lines and that would eventually attack the foam rubber. I'd go with the silicone rubber lub that is made for just that like Harvester suggested. Silicone can cause problems with repainting it the substrate is not properly cleaned, but nothing is so tenacious that it can't be cleaned up if you ever need to paint it.
RuGlyde Ken? We used that by the 5gal bucket when I was a greaser at the Chevy dealership back in the late 50's. I believe it was a GM service product back in those days. We soaked all the rubber suspension components with it on every grease job. I haven't seen it for decades, if it's still available let us know where we can get it; I'd like to get a gallon.
Denny Graham
Sandwich, IL
