My tyres are now 6 years old ,with 30k fabulous touring miles under their belt. have just passed MoT and major service without a mention and I'm wondering whether to change them. They are Michelin 215/75/R16C CAMPING tyres and have 5/6mm tread left and look ok. Don't want to take any chances but £500 for a new set goes a long way when touring. Goes anyone know the rules on when to replace ?