Correction - the regen is on the FRONT axle. If you move brake balance to the rear, the front axle relies more on the regen than actual brakes to slow it down, and hence it harvests more energy. The only cars that benefit from this for sure are the 3 new hybrid LMPs (R18 2016, 919 and TS050). Some of the VGTs might benefit (Pug, Audi) but I lack track time in these cars to know for sure.
It's essentially a braking distance vs acceleration trade off. Do you prioritise braking performance or acceleration? Also the 3 hybrid LMPs differ in their braking stability and regen characteristics:
R18 - most stable under braking (can use BB +4/5 to recoup more energy), but poorest regen under normal conditions (only recharges during braking)
TS050 - moderate stable (BB +3/4), moderate regen (recharge under braking + coasting)
919 - very unstable (BB +2/3), but highest normal regen (recharges under braking + coasting + on throttle (from MGU-H harvesting energy from the exhaust))
So as you can see, the 3 cars are all very well balanced actually, but in different ways. You just have to experiment to find one that suits your style.
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More trivia if you're interested:
- In F1 the regen is on rear axle, so rear brake discs are much smaller than front (because they don't have to work as hard). In the Canadian GP a few years ago, the Mercedes cars have a failure of their MGU-K regen system, so essentially the rear brake discs have to do all the slowing down now. Canada is a particularly brake heavy track and Hamiton had to retire due to rear brake failure (the small disc can't cope with all the extra heat). Rosberg managed to compensate by altering his driving style and moving the brake bias forwards. He finished the race, but only just.
- In Assetto Corsa's Ferrari F1 car, you can set different profiles of regen (how aggressive it is basically). This must then be balanced against engine braking map. Basically more aggressive regen --> you need to reduce engine braking (otherwise the rear axle slows down too quick - equivalent to pulling the handbrake and making the car very easy to spin). Reducing engine braking also diverts more exhaust gas to the diffuser, which increases rear stability (win-win basically), BUT it uses more fuel. Yup, other than being fast, you also need to juggle all these systems when driving