plucky

Try "Armor All" or silicone spray. These will make it look like new, but will need to be re-applied occasionally.

Check your shock absorber. I just had a similar problem and it turned out to be a worn shock where the shaft emerges from the body of the shocker. Lift it up and get someone to watch from the front or rear as you move the wheel as you have described. Ball joints and bushes can be checked with a pry bar and worn bearings will usually, but not always, feel rough or rumble when you spin the wheel.