Thanks Norman,

The new system I have had fitted is about 2.5” and my original were just under 2”.   The car runs better with these pipes but I was getting a slight tapping noise at the rear end.  Before going to a classic car show I checked the tyre pressures and they were under inflated. After correcting the pressures this the noise has gone so this must give a bit more clearance from where it is catching. I have informed the fitter that I believe these pipes are too large and await his answer.  I found a site on the internet that recommended larger pipes for upgrading the exhaust but not to go above 2.25”.  My system is bespoke so the shaping of the pipes is down to the quality of the fitter.   At this moment I am confident that nothing is catching but my concern is if you get some little wear on the hangers the noise will return.