On my '37, the springs were pretty worn out from hard use. I could tell by looking at the bottom side of each leaf. The one below had dug into the one above and created a step. Over time it became deep enough to cause them not to move the way they should and ride rough. Spend a little time and take yours apart to look each leaf over. The new center bolts are cheap at the local trailer shop or spring shop.
I bought new springs this summer. I had them back out two weeks later because of the stiff ride. I removed the two lower leafs and applied grease between the others. The ride was 100% improved. Joe
