One could argue about the quality, another about the distribution and many about the construction and handling of the tyre compared to more modern ones but essentially, the Dunlop CR65 remains and I hope will remain the only approved tyre for proper Appendix K racing.
The benefit of tyre supplier being put into competition could help the distribution and improve the quality, of course but another factor to take into account is the competition between them which could have the opposite effect of what you are seeking.
If any of you have experienced the old Michelin TB15 tyre years ago when Michelin was mostly the sole supplier and have compared it with the equivalent it is producing today, of course they are better but since Pirelli has come into this market, the benefit and improvement in compound as well as distribution has had the worst effect possible. Cost have gone up. Now the tyres are historic threaded pattern build with modern technology and compound and the result is for example, with the Tour de Corse, the top crews using up to 2 sets of tyres a day and 7 compounds being available on the market, you can only make the difference in mastering that. It has upset a lot of people in rallying as cost have gone stratospheric..! It can be compared with the championship using the Yoko or Toyo, of course they are better and cheaper but on a long term base, you spend more in buying tyres all the time. That's not what we want in an historic racing world getting more and more expensive..... Do we ?
Having recently managed a championship using the CR6ZZ on Pre-66' Appendix K cars, of course, there were no differences except for particular cars, when the people used to hammering the CR65 would show up, no differences or yes, they were faster. A more consistent tyre on long distance as the CR6ZZ proves very good at the start but tend to fade very quicky and more in hot conditions... Better compound...
The CR6ZZ with lower sidewalls, radial construction and better compound only proved to be harder on the cars with some chassis parts or suspension braking regularly... The average drivers performance was better as well as "wet races" conditions improved but a big problem was again, the cost, a complete set would only last a single weekend. The few who were using the CR65 proved to use their tyres on a minimum of a "long distance" weekend plus a "sprint" one.
Last, the CR65 does respect the design and handling the cars deserve and thats's what should be kept in mind. The sourcing and manufacturing has always been a problem and more for the continentals, cases of bad sets or complete lots of tyres have always been part of it, I remember looking after a Chevron at the 'Classic some 8 years ago and they were already square ! But when taken back to Dunlop they did change them and the car improved.
Keep calm and carry on
