I've got a question about tire pressure. I will be towing my boat from Arizona to BC in September. The boat trailer has new tires on it and the recommended cold PSI is 65. The spare that I have has a 50 PSI cold rating. If for some reason I do need to use the spare will it cause problems having tires with different pressures? It might be possible that I'd need to tow for a fairly long way until I could get a repair. Thanks for all your help.