Hi Pauline, Don't pump the tyre too hard as you shorten the life of the tyre, around 15 to 20psi, it if still bulging then add some more air but not 30 psi as quoted on some tyres, remember the harder the tyre the less comfortable it will be even with suspension. Ntpc turbine operation manual. Too soft and you will shorten the scooter battery distance as it harder to move forward ( Rolling resistance) Shoprider recommend from 22 to 25 psi. Hi Pauline, Don't pump the tyre too hard as you shorten the life of the tyre, around 15 to 20psi, it if still bulging then add some more air but not 30 psi as quoted on some tyres, remember the harder the tyre the less comfortable it will be even with suspension. Too soft and you will shorten the scooter battery distance as it harder to move forward ( Rolling resistance) Shoprider recommend from 22 to 25 psi.