Hi. I have just taken delivery of a new bike,after a few years of being bike-less. After assembling it,I went to pump up the tyres and read on the sidewall that it requires 75psi pressure. I thought that sounded a lot so pumped it up to 70 until I could check that would be ok. After half an hour the the tube went bang! So I wondered if maybe I even overdid it with 70psi. Does anyone know what the correct pressure would be? The size is 28X1 5/8. Thanks in advance.