The ABC Quick Check is a short, simple way to know if your bike is in working condition or not. I recommend performing it at least once a month, more if you ride your bike frequently. Note: The psi listed below is just a suggestion. Ride with what you find the most comfortable and effective. I usually run my bike (MTB tires) between 45-55 psi when I use it for commuting and 25-35 psi for mountain biking.