braking

[Tim.duncan]

hey guys

i was watching bathurst the other week, i love watching the foot cams on the differnt styles of foot work.

any way i was noticing how some kick the brake pedal just before they need to brake hard. iv had it explained that this is to clear any crap off the rotor so the brakes can work 100% when applied a second later. is this correct?

also would this be worth while on a spirited drive off the track?

last question, how hard does it need to be kicked?

[af300e]

They do it because the rotors warp from heat and cause the pads to move away from the disc. The front discs warp more than the rear and thus move off the disc more. If the brakes are applied after a longer period of non-braking the bias will be screwed up (too much brake to the rear).
A tap on the pedal just before hard braking brings the pads up to the discs and helps keep the bias as intended.

[silverra23]

Minute play in the front upright / bearings causes the brake pad knock off also - they can do the bearings up tighter, but that causes more mechanical drag, so they are constantly experiementing with where the fine line is between too much and not enough.

Hitting a kerb hard can also give the pad knock off.

And with an event like Bathurst, the pad wear means that the pads are further away from the brake disc also when they retract back.

But ultimately af300e is right - all these things are causes, and the brush of the pedal before the stop proper is to bring the pads back up to the disc before they give them a good stomp.

[jaz_ae86]

They are checking that the brakes are still there/ nothing has failed.

You want to know that when you go to jump on them at the last possible point that they are actually going to work.

[Tim.duncan]

so in a road car this technique is not needed?

since we would be hard pressed to get our brakes up to those sort of temps and conditions.

what if out at mallala with a rd car, which is a hard on the brakes sort of track?

just curiouse thats all

[Adsie]

There is no point in doing it if you are just driving on the street. I do it on the track though, just a quick tap with the left foot to make sure I still have brakes. This is only because I had an off at the end of the straight at lakeside because my pedal went to the floor and now have no confidence in them any more.

[Dongaz]

Only time I had to do this was after installing rx7 brakes up front while still retaining the S series diff and the std brake master cylinder. I had to do this to get the bias right so I had enough pressure on the front brakes or they didn't work aswell. Simple solution, get an r32 non abs master cylinder. Prob solved. Basically felt spongy otherwise.