how much air in a bicycle tire?
The tire usually has a PSI limit listed on it. It varies for different sizes and types.
Look on the tire sidewall. You should see a range for the proper tire pressure. Probably between 30 50psi.
mountain bike standard tires doesn't mean much. The specific tire width, along with the weight of the rider are used to determine needed air pressure. Bike tires have a pressure range embossed on the tire sidewall. If you are light, set your pressure to the low end of that range. If you are heavy, go to the high end of the pressure range. For example 26 x 2.30 tires for a light rider need far less pressure than 26 x 1.75 tires being used by a heavy rider. The tires themselves should provide you with the information you require
