Chronic flats can be caused by:
- Glass, wire, sharp stone stuck in the tire, flatting each tube.
- Poor technique installing the tire, causing small hole
- Rim strip on wheel slipped out of place, exposing spoke hole which cuts the tube.

You can use a cotton ball around the inside of the tire to see if it catches on anything.

You can also line up the label on the tire, with the valve. Then when removing the tire and tube, find the hole and match up with the tire to look for a cause.