The amount of understeer is ridiculous and totally unrealistic: I drove trucks for a living for 25 years, and sometimes we used to race round with the tractor units without a trailer in the harbours to have a bit of fun while waiting for the next tour. And they handled pretty well really, a lot of roll, but also enormous amounts of grip from what were of course just normal truck tyres. But they had nothing like the amounts of understeer displayed by the racing trucks, which have slicks and enormous amounts of grip. If they were really so bad in real life as they are in the sim, they would have to come in for new tyres every two laps.