spongy brakes

[NA Drifter]

Hi guys,
I always have spongy brakes after give the car a good workout at the track. Well, maybe that's normal, but even day after, it still feel spongy.. and also day after etc...........................

I have got Dot 4 and Lucas pads on the AE86(i tried Metal King but they hard on the disks). They ok for what i'm doing but is very anoiying it always feel spongy after track event.
Is this due to the brake fuild boil up(and moisture created etc) at the track during hard braking and they are "no good" any more?.. need to bleed it every time after track day is my only solutions etc?

Anyone have the same problem or suggestion? Or this only happen to my 20 years old + car/brakes.
cheers

[Akane]

I am sure it's the fluid boiling. Try some rangi air ducts to the discs (SW20 comes with them stock). And better fluid might help too. Ventilated discs also helps to disappate the heat.

[NA Drifter]

The AE86 have std vented disks on the front, solid at the back. Maybe the ducting will help on the track day etc, but will this prevent the spongy brake day after? Dot 4 not enough i guess? Someone said about dot 5.1 or something..? a while ago..... But pretty sure lots of peoples run Dot 4 too and don't think they have same problem..??

[GT4 20]

DOT 4 defiinately isn't cutting the mustard in this case. Get some pukka race fluid - I use Elf HTX and have no issues after blasting around Pukekohe.
Gary

[Malcolm]

try flushing your fluid completely with new stuff, just bleeding often isn't sufficient, as if the fluid is old and has moisture dissolved in it, it will boil at a much lower temp.

some useful information from Race Brakes in regard to DOT ratings

Now back to the DOT rating. All brake fluid, apart from silicone fluids, are hygroscopic which means that they will absorb moisture. Some people use the term hydroscopic. The higher the DOT rating, the less hygroscopic they are. In other words, the less moisture they will absorb over a given period. Over time this will contribute to a brake fluids “wet boiling point”. Using a high DOT rating in a road car theoretically means that you will not have to change your fluid as often as you would if you were using a lower DOT rated fluid. This however does not apply to a race car as a race cars brake system produces so much moisture and debris that the road car laws of longevity are not really relevant.


Keeping in mind that a DOT 5 is a silicone fluid, the highest DOT rating generally available for a conventional or synthetic fluid is a DOT 5.1 (notice the point one and we also note that there are DOT 6 fluids out there) So while a DOT rating has its place, what we are really looking for in a race fluid is a high dry boiling point. Interestingly, two of the best race fluids on the planet today, Brembo’s LCF600 Plus (this is the stuff that they tip into the Ferrari F1 cars and is available from RACEBRAKES 0800BRAKES in 500ml bottles) and Castrol’s SRF are both rated as DOT4+.
Incidentally, the minimum dry boiling point requirements of a DOT 4 fluid is 230 degrees C, DOT 5 (silicone) is 250 degrees C and DOT 5.1 has a minimum dry boiling point requirement of 260 degrees C. Admittedly, most off the shelf DOT4 road fluids will exceed the minimum requirements. In comparison, Brembo’s LCF600 Plus has a dry boiling point of 316 degrees C and Castrol’s SRF has a dry boiling point of 310 degrees C.

[Truenotch]

Braided brakelines help aswell.

[Kender]

I always had a similar problem with my AW11. In my case the sliders on the front calipers had seized due to the grease had turning tacky.

[NA Drifter]

I always had a similar problem with my AW11. In my case the sliders on the front calipers had seized due to the grease had turning tacky.

Thanks for everyone reply. I'll look into getting better fuilds and maybe braided line too.
I rebuild all my brakes before and I use anti seize for those slider instate of grease because I believe grease will melt at high temp.
The brakes not only spongey, but more travel too, but pretty sure there is still alot of life left on the pads as I had a look at them.

[GT4 20]

When brake fluid boils, it produces tiny air bubbles which all join up to form a pocket of air. Where the brake fluid itself won't compress, the air itself will, hence the long pedal travel. Get rid of all the DOT 4 from the system and replace it with something that has a much higher boiling point.
If you ahven't alreday done so, you can promote more airflow over the rotor by ditching the stone guards which are attached to the hubs - assuming that you don't do lots of gravel driving
Gary

[Perky]

Just a note:

The concern for a High dry boiling point for racing brake fluids takes for granted that the fluid will be changed frequently -- often after every race-day. Since this fluid is not in the system long enough to absorb much moisture the wet boiling point is less significant. For road cars, or cars with occasional track use, which do not have their fluid changed so frequently the wet boiling point is the more significant. Some racing brake fluids are only rated DOT 4 because despite their high dry boiling point, their wet boiling point is not as high as DOT 5.1 (though there may be other reasons).

However, DOT 4 should be fine. (DOT 4+ or Super DOT 4 are likely to actually be DOT 5.1 -- some manufacturers seem to avoid this confusing designation.)

[RS13]

On a side note, I was pretty skeptical about the "master cylinder stopper" modification, which is basically an aluminium brace from the cylinder to the strut tower.. after installing one in a Subaru, the difference is very noticeable, much firmer pedal, makes you feel more confident having super responsive brakes! I wouldn't hesitate to recommend it, but only if your car suffers from firewall flex under hard pedal applications..

Just a thought!

[jondee86]

I had this same problem with my 86. Brakes would work fine during
the race. But afterwards, by the time I would get back to my pit the
pedal would hit the floor Cause was heat soak from the hot discs.
I changed to a higher spec Castrol brake fluid and the problem pretty
much went away.

Cheers..... jondee86

[suckymotor]

if you get hold of stevo at 0800brakes he should be able to make up some brake lines for a good price (just put mine in last week) also best to get a set of pads made up with mintex 1166 all round and go with the elf brake fluid this works well have it on my car and never have had brake fade so far

[KinLoud]

Do you have a soft pedal or a long pedal or an ineffective pedal?

Soft pedal... where the pedal suddenly seems to go to the floor, often during or after a bit of hard driving (hot brakes).
Long pedal... the pedal needs to be pushed further than normal, but it is effective, it is like this even when cold.
Ineffective pedal... normal pedal feel, but poor braking action.

Soft pedal - caused by hot brakes boiling the brake fluid
- cure, new/better brake fluid, regular fluid changes, bigger brakes, ducts to bring cooling air.

Long Pedal - caused by pads wearing unevenly, i.e. tapered towards one end or one side, or caliper moving/tilting on the guide pins or a brake hose bulging. This means that the piston has to push further to make the pads contact the disk properly, therefore the pedal has to move further
- cure, put in new pads, renew caliper and or guide pins etc. or replace the brake hose/hoses. You can work out what caliper is causing the problem by using brake hose clamps to isolate one caliper at a time. When you clamp off the caliper causing the problem the pedal will become firm much earlier than normal. Check all the calipers before you decide which one is the problem.

Ineffective pedal - caused by overheated brake pads, coefficient of friction depends on temperature, some pads work well cold but are poor when hot. Others are poor when cold but great when hot (race pads)
- cure, better pads, if you drive to the track you might need to change to race pads at the track due to their (sometimes very) poor cold performance.

Long bit of babble sorry, but I hope that this helps you.

Ken
Hamilton
021 408 863

[NA Drifter]

......... If you ahven't alreday done so, you can promote more airflow over the rotor by ditching the stone guards which are attached to the hubs - assuming that you don't do lots of gravel driving
Gary

You will be suprice where the car goes to in the track.. kitty litter, gravel traps, big muddy pot holes,... etc etc which not very often, but on the grass is not uncommon. Have you seen any of the drifting footage on tv.. like XSTV?

if you get hold of stevo at 0800brakes he should be able to make up some brake lines for a good price (just put mine in last week) also best to get a set of pads made up with mintex 1166 all round and go with the elf brake fluid this works well have it on my car and never have had brake fade so far

I heard some good and bad stuff about mintex.
Good are from "racer" like you guys which found everything works great and you guys share the experince.

Bad, from rally drivers who have their mintex pad caught on fire!!.. due to heat build up... problem solve after try different brand.
And another one are from a mates car with the "mintex combo setup".. fuild and pads which suppost to "will not out driven them" on a street car that goes to track once in a while. Car owner told be he out driven the pads... at the end of the track day

I haven't tried Mintex myself, so i'm 1/2 here and 1/2 there.... if u know what I mean.

I have new brake line hoses and all new fluid which is less than 1 year old.



Ken,
I think I got... abit of soft pedal(but i doesn't goes all the way to the floor and still does it after the brakes are fully cool down), and ineffective pedal... just abit more travel.... or is that consider as "soft pedal"

When going into the track, 1st lap, i'll have not much brake, which must be due to pad is cold, so I always do warm up for more than 1/2 a lap for the tyres and brakes before going sideway...

So seems like, I need some better fluids and some ducting and will try to make up one of those "brace" thing for the master cyclinder.

[offensive]

i got lucas pads in my car, same sorta thing happend to me after a track day, they eventually came right tho after a few days tops