Remember this is from a brake point of view (work) and I am not a tyre expert:
Modern tyres are made on flexible production lines. The vehicle manufacturer therefore has two choices. He can buy whats on the shelf and test it, or have something made. The first choice is usually the only sensible one, but car manufacturers who want to style their vehicles (17" low profile etc.) will sometimes go the latter route. Having selected the tyre, the vehicle is tested, including type approval and released. The vehicle manufacturer then tells you to use Michelin whatevers as these WILL match what they tested to.
For the aftermarket people like Avon borrow a vehicle, look at the loads etc. and it lots of cases carry out a vehicle test before they publish their recommendations. The speed, acceleration, load, wear expectations etc. are all factors.
Whoever makes the new tyre then has to get it rated. This is test probably 50 years old that has two purposes, to give a level playing field and support vehicles that were never type approved. A tyre made in some Chinese boot factory is at least tested (the factory won't have seen a large bike), but it is a case of the lowest common denominator. You can also guess which tyre will work on a 1953 BSA and so on.
However, I'd want more that a guessed spec based on a basic government test. I'd go with what Avon reccomended on the basis that performance should be something like.
Andy
