My KHS Urban-X (awesome & cost effective, BTW) came equipped stock with Kenda Kwest tires, and tubes of an unknown make. The Kwests are rated at something like 40-85 PSI, and I've been filling them to about 60 PSI. I've noticed that no matter what, they lose air. Slowly...maybe 10 PSI a week.
I thought I might have some slow leaks, but they seem to stabilize around 30-40 PSI. I've let them go pretty long without filling just to see if they'd go flat, but they never get out of range.
Is the slow loss of air a normal part of riding, or should I maybe look into replacing the tubes? I've ridden the bike for a year and ~1000 miles, and to the best of my knowledge this has been cropping up since early on.