Hi there,

Just looking at a second set of tyres (slicks or intermed types) for track days.

I have been given the sizes of a set as 12x23x13.

What's that in old money (I can't work out if they'll fit my rims) ?

Cheers,

Mark

Normal passenger car tyres have all sorts of information on them, and unless you're either up to date, or have a particular interest, you're not really going to know what the nomenclature means.
Competition tyres, on the other hand, are categorised for the average numbskull petrol head, so they can work out rolling radius and thus overall gearing.
What you have there are competition tyres, and the sizing is quite simple:

12 is the tyre width in inches.
23 is the tyre diameter in inches.
13 is the appropriate rim diameter in inches.

The equivalent in a passenger car tyre would be 305/40 13.

Thanks Rorty. Much appreciated.