Flat tires can be caused by several different factors. Please ensure that the following criteria are always met:
1.) Tire pressure - Always maintain the air pressure within both scooter tires. The specified PSI (pressure per square inch) value is listed on the sidewall of the tire. It is recommended to inflate the pressure once it reaches about 4 PSI below this value. (so, fill your 50 PSI tires up once they reach about 46 PSI).
2.) Installation - When installing a new tube, always make sure to keep about 1 PSI of pressure in the tube. This will allow it to keep its shape and prevent any pinches or folds (these can cause flats). Also, tighten the main hub bolts in a star pattern to ensure even bolt torque.
3.) Hazards - If your tubes are consistently getting flat, please inspect the inside of the tire or rim for any sharp edges or objects. These can poke holes in the tubes and cause flats.