Hello,
I have Kendra brand bike tires for a long time. They appear to be cross type with a smooth centre for roads and knobby sides for off-roading. As visible from the attached image there are cracks that have developed along the tread. I was wondering what factor(s) would cause this condition. I ride mainly on pavement with gravel shoulders, often on the shoulder, and occasionally through dirt trails. The sidewalls recommends 40psi-60psi. I normally just inflate the tires to about 40psi.