I have an original drivers handbook which lists tyres as 155/65R13 73H and 165/60R14 74H. Unless the law where you live states otherwise I imagine any tyre which matches or exceeds this spec will be OK. I doubt if an insurer would be concerned unless a claim arose from the failure of a poor quality tyre. We should also remember that the Beat was designed best part of 20 years ago. Tyre technology has changed a lot since then and as a result the characteristics of a modern tyre may be notably different from a similarly designated one from that time.