Juz asking
After changing new rotor & pad thcar stopping power is much more better just when going to 80 & 90 km/h then suddenly stop the braking force is abit soft. Is like you know the car is stopping but you don't have the confidence the car can totally stop that kind of feeling.
Is it upgrade my rear drum to a 1.6 & 1.8 disk make it better or swap the brake line to steel hose type better?
Rear disc wont help much.
Certain type of pad esp high performance pad does not work well at normal speed. It takes a lot of heat to get it working. BTW, brake pad need to be run in too. Let me 'baked' your pad...heheheh.
For normal street driving, semi metallic pad is enough. In total, braking rely on other factors too such as tires, suspension, chassis, apart from the brake system itself.
From my experience with my mum wira 1.5 auto long time ago, braking is sufficient. U just need to trust the system and press the pedal slightly more. That is provided the brake system is regularly maintained with fresh fluid, rear brake shoe properly adjusted, using decent brake pad & shoe.
The stopping feeling depends on the car weight, suspension, chassis. Cars like Viva will put on a show when stopping hard from 80kmh. Its throwing mass all over the place. Modern car with decent handling and chassis can hide all these and provided u with a composed body control.
Bigger servo definitely help but too big is bad as braking will be an ON or OFF affair.