Morris Minor Owners Club

I thought I'd investigate what tyres were currently available from a specialist old car tyre supplier and found the following interesting detail.

145 tyre width = 142mm
155 tyre width = 148mm

I knew the measurements were nominal but that's a bit too close eh? And also bear in mind that on some brands there is a pronounced shoulder that reduces the effective tread width.
As if finding tyres the width of your choosing wasn't hard enough

A 145 is wider than you need anyway on a standard saloon rim, so a few mm undersize is no problem.
135's are also fine, but no longer available.

Well I'm looking at getting wider tyres for van rims. With that sort of rough interpretation of tyre sizes I'm going to have to look very carefully if I'm not to waste my money.