it's a moving target, but iracing v7 model is one of the best, for the cars that have been ported to the v7 model.

RFactor 2 does degradation best tho. so there's that.

some random background info:

https://www.iracing.com/physics-modeling-ntm-v7-info-plus/

https://www.beamng.com/game/news/blog/tire-physics-changes/

I work in the industry and always thought iRacing model was the most detailed but wanted to know if someone knew a better model.

It's a shame they don't license their models for engineering customers (like rFactor does), since it's a single made-up parameter set tuned to make things feel "real".