On a bicycle

I have a Bike Friday Pakit bicycle. It folds in under 30 seconds to easily fit in my car trunk. The ability to do that comes with a caveat: it requires a few more parts, and they can do things like creak or loosen enough to make the bike wobbly. The drive train and back of the bike pivots down and forward around a hinge just above the bottom bracket. Several dozen miles into owning it, I heard a creaking noise with each turn of the cranks. Most times a few drops of WD-40 indicated the hinge as the source and I'd take the hinge apart and smother the parts with grease and put it back together again. Once the creaking arose from the seat mast or seat post--I'm not sure which--I greased both parts at the same time. Creaking hinge chapter 813. I removed the steel washer and replaced it with a nylon washer. I added a nylon washer to the other side. A few miles into a test ride, the bike felt wobbly--tightening the nut compressed the washer on the nut side. Creaking returned as did