Looking for new road/trackday tyres for my car I came across lots of references to numbers like "120" , "180" basically in describing the compound softness.
Apparently its an index developed in the USA. to measure grip in standardised way.. Relying on Wiki as ever its here https://en.wikipedia...Quality_Grading
In the treadwear section the methodology of using a special control tyre and the candidate tyre is explained.
The interesting bit is the formula to convert the index , 100, 180 etc, to actual grip. It is mu=2.25/TW^0.15. where TW is the treadwear index
So going from a TW of 180 to 100 in the formula suggests a 9% increase in grip , or at least friction co - efficient..
That is huge grip increase just from compound change. Some tyres in the MSAUK list 1b, i.e "road " tyres for racing, sold in UK come in compounds of 100 to 180 so , if it is true I gain 9% extra grip by buying a variant of the same tyre?
This seems a bit too good to be true?? a clue might be here in the Wiki article "The assigning of UTQG grades is done solely by the tire manufacturer. In many cases, this has resulted in the UTQG grading system to be more of a marketing tool than was originally intended".