Crack on clamping area. This aluminum crack developed on the mount I use for my tailbox on one of my bikes. You can see the outline of the clamping washer. The material is anodized aluminum 1/16" thick. I replaced this mount with a similar mount using 1/8" thick aluminum.
The mount had lasted many years, but recently I had begun to carry spare batteries in my tailbox, and the extra weight was too much for the 1/16" aluminum.
