Beautiful spring day, so I dragged out a coaster, cleaned off the dust, lubed the chain, aired up the tires and checked for cracks. Hopped on and took a ride around the block, did some tight turns and hard braking, all systems go. Went back to the house and sat on the stoop for a couple of minutes, and.... POP!! Sssssss. Fortunately, I have some fresh spares.