Brakes Failure

[Travis Trayhern]

OK last year at legend of the lakes hillclimb it only happined about twice out of 8 runs but when i got to the top of the hill doing 200km/h+ i hit the brakes and they where rock hard as if there was no vacuum left for the booster and just managed to pull her up in time for the 90deg turn.

I know if i back of abit up the hill ill have some vacuum for the top but this isnt an option as i want to win, has anyone got any ideas or come across this? a few of the rally boys told me to just run a bar through the booster they said it would be hard but you have total controll ova the brakes and thats what they do, but i dont want this because its a steet car to.

[battery]

that sounds farken scary!

[HuH]

Wish I could help mate, but I don't know the answer - sorry. I just wanted to quote this because it's awesome:

I know if i back of abit up the hill ill have some vacuum for the top but this isnt an option as i want to win

That's the spirit you mad man.

[Travis Trayhern]

lol yeh but this year i want to win i placed 3rd last year and done alot of mods to the car this year and sponsers have spent big money, and really dont wanna be doing 200 looking at a concrete barrier with the handbrake fully pulled out of the floor i yanked the thing that hard i recon i streched the cable and just pointed the car where i wanted it to go and shut my eyes lol

has anyone hurd of a vacuum auxilary tank or an electric vacuum pump? and where to get one

[blind_elk]

Have you considered that the one-way valve in the vacuum booster hose might be cactus?

[Travis Trayhern]

no i havent but its only under extream conditions so there is no way to test is there?

[robbieraver]

may be there isnt a problem with booster,if the pedal goes hard then it sounds like pad choice?

if it only happens under extreme condtitions then the pad could either be not up to temp, say after a longish straight (200 km) on the climb and you havnt braked for a bit..

just throwing ideas out there.

[Travis Trayhern]

raced on standard pads so should have been rite they wk fine cold

[djr81]

no i havent but its only under extream conditions so there is no way to test is there?

Yes there is. Left foot on the brakes, right foot on the accelerator. Just use enough throttle to get the boost +ve. Then you can make some comparisons with someone elses car.

[Travis Trayhern]

thats another thing i was doing left foot brakein up the hill, what i will to is take it out and give a clean out and see how i go but i found this but they are sold out and will take 5-8 weeks for new stock to come in anyone know where i can get one

Vacuum Brake Auxiliary w/vacuum Gauge Part No Application

TEN-7730 Vacuum Brake Auxiliary w/vacuum Gauge

[nuclear_skyline]

I have seen aux. vaccum tanks that we used on vaccum operated pop-up head lights....

[enilyks33r]

A vacuum pump is required, a storage tank is also a good idea.

Diesel vehicles are the best place to fid one as they have no vacuum to operate brakes by default.

These guys make pumps and have info you might find useful:www.wabco-auto.com/products_and_systems/products-systems-vacuum-pump

[White GTS-T]

Just do what the V8 supercars drivers do. Give the brake a little pump with your left foot just before your about to brake to ensure you have pedal feel.

[Lunatikk]

Just do what the V8 supercars drivers do. Give the brake a little pump with your left foot just before your about to brake to ensure you have pedal feel.

I don't think that (pad knock-off) is the issue here. I've seen this happen a few times on both our toys & old-school blown V8's, once with an impact at the end (ouch) & the cause is instead of the brake booster seeing -ve pressure (a vacuum), it's is being fed +ve pressure from the turbo/'s or supercharger via the plenum. Now I know that shouldn't happen, but sometimes it just does, for whatever reason.

The fixes:

Run less boost/ lift earlier but as Travis has already said himself, "this isnt an option as i want to win"

Disconnect & plug the vac-line. Will def stop the prob but at the cost of vac-assist & possibly feel etc.

Pedal box. As above, but at a higher cost.

Go with the vac-tank/pump assembly. Problem solved

By rights the check-valve on the vac-circuit should stop this from happening, but if it's failed once do you really want to risk it happening again or have it in the back of your mind, f**king with your sub-concious & maybe slowing you down "just in case" without you even realising it. Piss it off, & go collect a trophy!!

Good Luck

[Roy]

raced on standard pads so should have been rite they wk fine cold

Often its the simplest things. You are doing 200km/h on std pads then stamping the brakes and wondering why the hard pedal doesnt equate to retardation? Tells me the fluid is fine as you have line pressure and pedal pressure, the thing jsut isnt stopping which tells me the pads could be glazing, are the rotors std, slotted?

Pads can change pedal feel a lot. Some will make you think you have wooden planks as pads, so hard pedal but just so much pedal effort to try and stop the thing, others are bitey...all feel and react different. If youa re runnig std pads, along with what others have suggested i would not stress too much, its always the simple things.

[robbieraver]

pads, you are using a standard compound in race conditions,our shop sets up lots of traga and dutton cars and never use a standard pad, roy is on the same path, start simple. think about what the standard pad was designed for and the maximum temps it can with stand, not much, it will fade very quickly trying to haul up 1500kg traveling at 200km.

there are plenty of great pads mintex, pagid, ebc the list goes on.

rotor condition as roy pointed out also is just as important, keep it simple.

[donkey]

hey there, sorry for the dumb question. but how does it effect your brakes if you 'back of a bit'

cheers

[blind_elk]

Yes, you might have cooked the pad, especially left foot braking. If you were resting your foot on the brake pedal even the slightest, you could have been adding frictional heat.

I've "been there, done that". Calder, 240Z, stock brakes. Million miles an hour down front straight, into 150 m, STAND on picks, sideways into turn 1. Next time round, same thing - Oh Shoot! hard pedal, absolutely no retardation. Good thing the gate was open on the escape road!

[Duncan]

I am willing to bet the left foot braking is the problem. well not a problem but it impacts the braking vacuum assist.

Anytime you have full throttle there is no vacuum. when you left foot brake within a couple of seconds there will be no vacuum left in the cannister, even with a properly working system. I get the same problem in mine across the top of wakefield where I keep pretty much full throttle and a couple of dabs of LFB to bring the nose back around.

[Tomei_33]

dont know if this helps, but when i drive on the street and tap the brakes with my left foot (while accelerating), the brakes are real stiff, then i let go of accel and brake and its normal again..

reason why i do this is coz my friend always tail gates me, wanting to race, so i flash my lights to annoy him