how to simluate smooth drift of car

I have set lateral and longitudal of tire as follows:

front and back tire:
m_tirelongstiff=1e6;
m_tirelongexslip =1.0;
m_tirelongexvalue=0.02;
m_tirelongasslip =2.0;;
m_tirelongasvalue=0.01;
m_tirelatstiff=1e6;
m_tirelatexslip =1;
m_tirelatexvalue=0.02;
m_tirelatasslip =2;
m_tirelatasvalue=0.01;
when the car is drifting ,I reduce the front latstiff to 1500,back latstiff to 1000, longstiff of front and back tire to 1e5, to make the car slide almost without speed lost, it's good.

but whenever I dont want the car drift, I set the params back, the latstiff is suddenly added to a high level, because of huge lat friction, the speed fall off suddenly as well, how can I solve the problem?
car is driving at high speed:
1.when drifting, the car turns at a steady speed, no loss
2.when drift ends, the car turns back and recover to driving pose little by little, little speed loss.