Help. As title, the dust caps are stuck on and I need to blow up a tyre! Some swine stole the last set and the local garage didn't have normal black rubber/plastic ones so I bought metal ones - obviously cheap **** - and now they won't come off. Tried half a can of WD40 but no luck. The whole rubber valve just turns now. Other than risk scratched allows at National Tyres and have the tyre removed and valves replaced, any other suggestions??