Long race issues?

Am I doing something wrong in these long showcase races like goliath?

I’m way ahead in front for the first 15 minutes of the race, no crashes no nothing, but then suddenly the car performance falls off a cliff, the car can barely stay on the track and slides everywhere like the tyres have gone and the other drivers come from nowhere and pass me.

The same happens in other long races I’ve attempted too.

Maybe you are driving with full car damage?
In this case your tires wear down, pretty fast even. Depends a bit on your driving style though.

I am driving with full car damage tbh and that did cross my mind but seems weird that tyre wear would be modelled when you cant view it or pit during races like in forza motorsport

It’s just part of the simulation. You need to be careful.

Well, to be fair, Motorsport is on short circuits so you pass the pit every couple of minutes generally…not sure how it would work on 20 minute+ laps?