Tyre keeps coming off the rim on my Dahon

[onb]

Its the right size tyre ,its not over inflated ,no sign of any obvious damage to either tyre which is 6 months old , probably been ridden a couple of hundred miles , or the wheel rims . Any ideas would be welcome . Its on the rear wheel BTW .I replaced both front and back tyres at the same time and have had no issues with the front wheel .Tyres are Swalbe .

[Brucey]

possibly a faulty tyre. Some schwalbes fit OK to start with but work loose over time; running at lower pressures accelerates this process considerably.

cheers

[aidan.f]

That comment interests me. I have had shwalbe ones and duranos blow off. FWIW I also understand that once blown, a tyre is scrap.

[Brucey]

tyres with wire beads are typically  constructed using two or three turns of steel wire. This is kept from unravelling by a combination of tyre pressure (which forces the bead against the rim hook) and the fact that, in the mould, the rubber ought to infiltrate the wires and hold them in position.  However if the tyre is badly made and/or run at low pressure the bead can simply unravel. 

Folding tyres are a different kettle of fish and so are tubeless ones.

If a tyre has blown off the rim then it may be that there was a low spot (i.e. part of the bead was in the rim well) in which case that tyre may still work OK on that rim provided it is correctly fitted. But if it comes off the rim without there being a low spot this means that the tyre probably isn't ever going to be 100% safe on that rim; either there was always a difference in the size of the tyre vs the size of the rim or the tyre bead has been damaged.

 I have encountered some combinations of tyre and rim where the two together wouldn't ever be safe, but each could be used with other parts (of different manufacture) and it would OK.

cheers