My dear friend: the best tire is that one which at that point in time gets you the fastest round the track using the means you have.
We build a car back then with nothing, the 1992 championship was won on the racebudget of 1 (ONE) factory build race engine. In pounds and coins: about 12000 UKP for 18 races, fees and fuel included. Of those 18 races 16 were won.
We build a car strong where it had to be , flimsy everywhere else. The flywheel of a standard 2cv weighs 11 kg, ours was 2,75 kg...
A shaved junkyard-salvaged tire goes better than the junkyard-tire as it is. I don't know that from a European Streekbike Champion, I know that from experience.
We still race now: grasscart, the fast ones, Yamaha R6-engine, full spaceframe, home build from scratch, not using fancy steel only soft construction steel, 300 kg, 0 to 100 kph on dirt in 2.9 sec. There were have now Gold Speed Red Tires, which even on dirt heat up and become very sticky. 1 tire costs more that 16 2cv-tires (rims included) back then, I would even mention the magnesium rim of our racer now. We can afford it now but then we hadn't the money but we had the time. Now money is not the problem, time is...
Our crosscart can not be bought nor sold: in one chassis goes about 700 hours of work. It is CAD-spacial calculated in such a way that every part of it is as strong as it needs to be. That chassis weighs 29 kg, the commercialy for sale weighs 45 kg.
If you fight factoryteams and win, you don't win by buying "the good parts" or the top motor, you win by being smart and *making* the good parts. You can do that 1 year maybe 2 and then the factory will give you the options: get out or work for them.
I -even then- never quite liked to work for a boss. I also found out pretty quickly that in Belgium it was not possible to life form racing unless you sold yourself either to a manager either to a company.
Tom De Moor