What's a good air pressure to have when putting air in your bike tire?

i have a road/racing bike

1st you are limited by the PSI range listed on the tire. The pressure you want to run depends on preference, tire width, weight and road conditions as well.

All narrow road tires require high pressure at least 90 PSI not to damage rims or get pinch flats. The narrower the tire the more the pressure needed. A 25cm tire may be good at 100 PSI for you, but a 20cm tire may require 110 PSI.

The heavier the bike and rider the more pressure is needed a 200lb rider needs more than a 125lb rider.

Road conditions can determine PSI too. You may want to run higher PSI on smooth roads for speed. On a bumpy road you may want a little less to absorb the road shock.

Finally preference. For a smoother ride a little lower pressure and wider tires work well. For more speed a little narrower and higher pressure is best. Just because a tire is rated to 140 PSI doesn't mean that's what you should run that much. Too much pressure can make a harsh ride and actually be a little slower on all but the smoothest roads.

Most performance riders use 23 to 25cm tires with 95 to 110 PSI. This offers the best PSI range for speed vs comfort for the average cyclist.

road bikes are usually around the 110psi mark. thats what i put in mine and they are perfect. i certainly wouldnt go any further than 120psi.

It says on the tire.
Every tire width and pressure is unique on a road bike,as your body weight matters.

I hope this can be of some help to you

The recommended tire pressure will be written on the tire. Usually road bike tires are over 90psi.

it depends, try some gauge that will determine its PSI.

15LB PSI