Remember, brakes are a strange part of karting...
As you probably know, your front brakes do most of the braking in cars, bikes and motorbikes. You can tell this (on motorbikes, most clearly) when you look at the total size of the disks on the front compared to the ones on the rear. Some bikes have two MASSIVE disks on the front and a tiny single one of the rear. If you watch some motorbike races, the rear wheel doesn't even stay on the ground under full braking and that shows you how little braking the rear can deliver.
The point being, the rear brakes on most vehicles don't do much of the braking at all.
However...... in karts, we (mostly) ONLY have rear brakes...... why? Longer braking distances gives more chances for overtaking manoeuvres. Kart racing IS about overtaking (well..... close racing). The secondary reason we don't have 'fronts' is the cost! We really have designed (most) karts to have pretty6 poor braking! You'd feel this most if you try a kart with front brakes as well. The difference is simply night and day! On a good, four-wheel-braked kart, braking really can HURT!
The reaction is simple. Crudely speaking, the best braking happens just BEFORE you lock the wheels. Thus, if you CAN lock the rear wheels, you can't deliver MORE braking from your pad/disk combination! Thus, in very crude terms, if you can lock your rear wheels, you can't make the brakes work any harder by selecting the pads/disks.
The simple reason why rear brakes don't work as well as front brakes is because, under braking, the nose of vehicles drops (and increases 'weight') while the rear rises (and reduces 'weight'). Under heavy braking, the front gets 'heavier' and that means you can apply more braking.... which increases the front 'weight'.... which means you can apply more braking.... which.... etc.. With rear brakes, it's the reverse: as you brake, you 'lighten' the rear and that instantly limits the maximum possible braking.
The implication is that, because we can't do a HUGE amount of braking on the rears, the brakes really are NOT as critical as they are in other classes of racing. Most of the difference in rear brakes is the amount of FEEL from the pedal and the ability to CONTROL (modulate) the amount of braking. Different pads will alter that 'feel' but they won't improve the 'braking distance' by very much, other than your ability to CONTROL it better.
The point is, the different pads really DON'T make a massive difference to your 'stopping distance', just your ability to control it.
This is a controversial view but..... think it through! If others read this.... there will be an argument!
Finally, you can also alter the braking 'feel' simply by moving the places where the brake pedal and master cylinder lever 'meet' their 'cable' or pull bar. If you RAISE the cable on the pedal, you will make the brakes feel heavier and the pedal will move less far to get the same amount of braking and will reduce the 'subtlety' of your braking pressure. If you lower the cable, it will increase the pedal movement and make the braking feel more controllable and 'lighter'. The exact opposite happens if you move the cable on the master cylinder. Both of those can be used to control your 'modulation' of your braking as well as the pad-choice.
I hope that helps.
Ian
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Brake pads: hard or soft? by 'DCharity' (24 Nov 2014 @ 17:35)
