For all struggling with understeer/oversteer postpatch midrace
Most of this will likely come through tyre temperatures.
Even with a default setup the worst car in the game can take corners flat which some on here claim to to be able to, its all just a matter of the approach.
First dont apply pre patch tyre pressures, they lead to fast overheating, on tracks like Suzuka the softs will even get to the limit on minimum pressure after a while when you are not subtle in you steering!
Second even when you think you have low enough tyre pressure look at the degrees! Anything above 100°C is costing you 1% grip per degree C.. In other words when you have 102° tyre temps you are running a one step harder compound in terms of grip and so on, thats really causing a lot! When its only the front tyres you will understeer even worse, when its the rear that overheats you will easily spin due to oversteer!
Default setups do work great when you lower the differential and do some practice runs to see when what tyres of the softest set you want to use are nearing 100°, when its only after like 5 consistent laps it might be fine, if you are at 100° after your 2nd lap you need to lower the tyre pressure.
When you are getting high temps even with lowest pressure, try steering more subtle, if you understeer like that try a bit softer suspension on the front but not much! Its not easy but the less you need to steer for making a turn the lower the tyre temps will be!