Originally Posted by
Christo613
Thanks folks, I appreciate the thoughtful feedback. To answer Icemilk, I did pump it up to 70 psi, the maximum recommended on the tire.I realise that's pushing it, but a local bike mechanic recommended that. I wasn't going to keep it there, but the idea was that if it's fine at that pressure, then it's solid. I will try one last time following Garthr meticulous instructions. I'll also pay attention to pressing the valve in, which I didn't really do.
The A319 on the picture is different than mine. Mine does say tires from 28 to 50mm. What it also says, which I hadn't noticed before, is a max pressure of 66 psi for a 50mm tire. I went very slightly above that.
First off, as others have already said, in the past, mountain bikes have had 17mm rims fitted to 53mm tires and they didn't blow off. So this tire/rim combo should work just fine.
Second, while 70 PSI is way too high to be practical for a 50mm tire, it is not much higher than the 66 PSI listed on your rim. So that wasn't the issue, though you will get a very harsh ride at this pressure. 30-40 would be a better pressure.
Lastly, my guess is that your tire blew off the rim because it wasn't seated correctly in the first place. When you mount the tire, air it up to around 40 PSI and then carefully check the bead on each side. If it is not seated properly at that pressure, you need to do it over.