whats the brakeengine setting?
The engine brake map setting controls how agressively the engine brakes the car when downshifting. #1 is the most aggressive so you have to be aware not to lock the rear wheels with too fast downshifts especially the lowest 2 gears.
You can think of the higher numbers like downshifting your mums 1.4 petrol for slowing the car and #1 like downshifting a tractor engine. If you are using a lot of engine braking you will normally have the brake balance slightly more forwards*.
*Trivia, Morgan Morand uses this technique.
When I've heard the sky f1 commentators about China, they always stressed the importance of letting the diff setting make a over-steering balance. On power out of corners I can see how that is made, but on corner entry?
Summary: Less lock more turn, more lock less turn.
Details.
In essense the more locked the diff the more it wants to go straight. So you use lock to eradicate oversteer. Power side deals with accelleration (turn exit) If its over steering on exit add lock, understeering lower lock.
Coast side deals with braking. If its over steering on entry add lock, understeering lower lock. The tyre wear connection is that while the diff is trying to make it go straight the front tyres are trying to make it turn. So the more open the diff (lower lock number) the less stress on the front tyres.
So less coast diff lock on turn entry will save front tyres and also allow you to get to the apex easier.
Excessive diff lock will impact you pace most when tyre wear kicks in. The fronts will give up the fight and the diff will get its way and make you go straighter.
Too little diff lock will hurt you on worn tyres too but mainly on power side as the rears lose their grip you will get oversteer moments.
In real F1 they will risk a lower diiff lock in quali (low fuel fresh tyres). Its set in cockpit and not part of parc ferme.
In Bahrain Turns 12 and 13 are a lovely example.
Lock on the power side will control the climb up T12. Too little and you will oversteer, too much and you will hurt the front left.
Lock on the coast side will control entry to T13 (as will getting off the brakes so the fronts can rotate.)Too much and you will fight to get apex, too little and you will over rotate.
Preload: Controls how early the lock settings kick in or how long the diff is free. A low preload number they kick in late and hard, high number they kick in early and gradual.
If between 2 numbers of diff lock you can change the pre load first to see if it works.
Compromise:
The diff probably will not be perfect for all corners. Perfect for one may be too litle or too much for another. You need to decide which one is "the money shot" in your race. Where will you gain or lose most if its not correct for that corner.
Edit:
I guess its fair to say that as you become more competent with the car and all the other set up options the less you will need to lean on the diff for control. Also other changes you make might influence your diff settings. If you for example add some rear wing or find more rear stability through other settings (springs/dampers) you may well find you can lower diff lock.
NB all this advice is "all other things being equal" and deals with diff in isolation. There are many other things that will contribute to turn in.
