Tire Lesson 102 - Manufacturers can only afford to produce tires in a range of diameters that they hope will sell in volume. As the performance level of road cars has improved then the diameter of wheels has increased ( larger brakes ) and the profile of tires has reduced ( 70,65,60,55,50,45,40,35 etc ) One can only assume that when the T & C rules were set up ( 1970’s ? ) they made allowance for the then gradual increase in Tire diameters 13” to 14” and 15” to 16” that the availability of suitable tires dictated. For us greybeards in 2014, to still be expecting to purchase performance street tires in 13 to 16 diameters when the manufacturers have moved on to 17” to 20 “ production is getting to be fairly futile. This situation is very bad now and only going to get a whole lot worse.
Yes, there are a few manufacturers still producing reasonable performance tires in small widths for 13 to 16 “ rims and some still making ‘cheater type’ tires but to find larger width, performance street tires in these sizes, is like finding the rocking horse doo doo.

Maybe it’s time for a re - look at tire diameters under the T & C rules . Auckland based Production Muscle Cars class don’t allow Willwood brakes, Dry sump engines, Yeriko Gearboxs etc but have made allowance for larger diameter wheels to cater for readily available street legal tires !

p.s.. Hey Ray, what’s this “tyres “ language ? Here was me thinking you spoke the Queens English !