bigger brakes = more friction.
locking up occurs when the friction in the brakes is equal to or great than the friction between the tyres and road. you can have any brakes you want but they are still limited by the grip of the tyres. if your current brakes can lock up then realistically your new brakes wont be able to make you stop any quicker, the tyres are still the limiting factor.
so you're probably wondering whats the advantage? having more pistons on the calipers, and larger pads and discs, will give you more control over the amount of braking effort you use. it will also spread the pressure over the pads more evenly and over a greater surface area, that means less heat build up per unit of braking effort, quicker heat dissipation of any heat that does build up. with more control and feel you can take it closer to the point of locking up so in effect you can actually slow down more quickly if you dont have abs and you have good skills with the brake pedal.
sounds good, but then you need to consider if your brakes are really insufficient. on a 200bhp punto GT you can easily get into a situation where your brakes suffer from brake fade. having driven GT's in the past i've never had a lot of confidence in the stock brake setup, they lack feel and control, and its hard to judge when locking up will occur.
i think spending money on a brake upgrade is fully justified on a 200bhp GT, actually i think its an important upgrade, but i personally could not justify spending £500 on the front brakes because it wont deliver the results you want and its a bloody fortune. all you really need to do is get decent discs and pads front and rear. you want discs that will lose heat more easily and pads that can operate at higher heat levels without fading. some extra friction would be a bonus too but you only need a different pad material rather than a change in contact area. you dont need bigger brakes and multiple piston calipers to achieve it, and you definately dont need to spend £500. just get some better discs & pads, and change all your brake fluid using good quality super dot4. if you still want more stopping power after that i would get some better tyres. good rubber makes a hell of a difference.
