Hi terence, a question that have made me sleepless many times,, :-). Why do grip level in corners, especially thight ones, increase if you slightly "left brake" while adding throttle ? have experienced this with both shifter karts and "only rear brake`s"
If you haven't got superb throttle control, then using the brake to hold the kart back is a much better way to keep the kart settled through the corner. For example, I coach some drivers to power brake rather than lift because when they lift without enough finesse and lose grip.