Hi Guys,
For road use I have always used 185x70x13 as I have always wanted as much rubber on the road as possible at any one given time!
These are becoming increasingly hard to find as no one uses this size on a modern car.
With the modern rubber compounds 165x80x13 should be comparable but you will probably get people on here recommending 185x60 or even 50/55.
Probably safest bet readily available is 175x60 or 70 if you can find them. Go for the best you can afford with a branded make, as something from Romania just does`nt look right!
Race tyres are something else, I would let Louis answer that when he reads your post as he has had the experience but, it will probably be along the lines of Colway remoulds!!
Andy M