Don't use WD-40 on rubber parts. Use silicon spray lubricant or the stick lubricant that you can buy at hardware stores to lubricate shelf slides and which contains bees wax. I think you can buy that kind of lubricant at auto supplies also. Or you can send your wife (or sister/girl friend or self) to a sewing/fabric store to buy a chunk of bees wax. But make sure you get bees wax, not tailor's chalk. Or go to someplace that sells a variety of honey. But no WD-40.

Harvester