Are you sure it’s E178 and not E78-14? I cannot find any conversion charts with an E178 size.
The chart at http://www.vintagecarconnection.com/vintage_tire_size_conver sion_chart.htm
says an E78-14 is the equivalent of a 185/14, P195/75R14 or P205/70R14. The first is an 80 series, then 75 and 70 series.
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica Roadster
If you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)