Help:- Brake Fade Problem

[sky30]

Im having a pretty bad brake issue, I have a R32 GTS-4 with ABS, i have just put in new QFM K500 pads and fresh dot 4 fluid.

The brakes work fine when driving on the highway and jump on them, they pull up good, but when i go through the hills after about 5minutes of cornering/ braking the brakes dont work real good and pedal will push in alot further. After i drive them on the highway again for a while they return to normal.

Can anyone suggest what my problem could be and what i need to fix?

Is it anything to do with the ABS Unit?

Cheers

[blind_elk]

What's the temperature rating of the pads? At $80 a set, I doubt they are "high performance". Get some Ferodo 2500s, or Bendix Ultimates (or whatever replaced Ultimates).

And use a Dot5 fluid.

Then get braided brake lines.

[sky30]

What's the temperature rating of the pads? At $80 a set, I doubt they are "high performance". Get some Ferodo 2500s, or Bendix Ultimates (or whatever replaced Ultimates).

And use a Dot5 fluid.

Then get braided brake lines.

Pads are 500 or 550 celcius temp rating, they are meant to be a performance pad similar or better than Ultimates.

Is 500 degrees high enough temp range?

Anyone else got suggestions?

[Bl4cK32]

only thing i can think of is like u mention that something is getting hot and allowing the pedal a little more play. Old brake lines may be the cause if the fluid is heating up and making the lines soft / swell...?

Cubes i think said he had the same problem a while ago too..mines setup for daily driving so i dont really jump on and off the brakes a lot now days

Edited December 16, 2007 by Bl4cK32

[sav man]

a guy down (wogboy) here used to have QFM pads, they were shit, lasted 1 run at symmonds plains (5 laps). Try differnt pads.

[sky30]

Seems to be a few people using QFM pads on here that rate them well, anyone else had bad experience with them?

Black32:- Yeah the pedal get a soft spongy feel, do you know what joel replaced?

[sky30]

How much do braid lines help?

[dangerous_daveo]

Well I guess QFM make more than one pad, are the ones you running the ones that everyone else is saying is good?

That, and as said above look at your brake lines. I found the difference to be pretty big. I like a realllly solid brake pedal tho.

Other thing, maybe look at getting your calipers serviced if you havent done that for a while.

[BHDave]

i found bugger all difference between rubber and braided lines on the street. everything else was done prior to lines though (caliper/rotor/fluid/stopper/800 degree pads). I swapped them before seeing track work so can't comment there.

All i can suggest is flushing the lines with the higher temp rated motul or penrite fluid and see how it goes first as thats a pretty cheap check. I'd be looking at the pads before the lines though as what you are describing sounds like you're cooking the pads IMHO. I found the same thing when i ran RB74's and a cheap shit interim pad while waiting for my good ones to arrive.

[gslrallysport]

Im having a pretty bad brake issue, I have a R32 GTS-4 with ABS, i have just put in new QFM K500 pads and fresh dot 4 fluid.

The brakes work fine when driving on the highway and jump on them, they pull up good, but when i go through the hills after about 5minutes of cornering/ braking the brakes dont work real good and pedal will push in alot further. After i drive them on the highway again for a while they return to normal.

Can anyone suggest what my problem could be and what i need to fix?

Is it anything to do with the ABS Unit?

Cheers

The K500 is a rebranding of QFM's pads. QFM don't make a K500 pad, they make a HPX which is 550 degrees. This 'K' packaging is what the southern distributors re-box the QFM pads as.

Assuming that what you've got is actually HPX, then I wouldn't both trying DS2500/TRW Lucas/Bendix Ultimate/EBC Green Stuff, as they're all pretty much on a level playing field in terms of performance.

QFM make a 780 degree A1RM (what the southern boys call K750), which is a big step up again, and similar to EBC Red/DS3000 etc.

Doesn't sound like the pads though, more like fluid I'd using something better than a standard Dot 4, like an RBF600 fluid. Also much better fluid takes away alot of the advantage of braided lines as the fluid stays stable to for longer. Definitely start with fluid, and then work from there.

This is what we use and recommend:

http://forums.justcommodores.com.au/gsl-ra...rake-fluid.html

[Edit] The above is $55 for a 1L bottle.

Edited December 17, 2007 by jetpilot1986

[Abo Bob]

As Mr Jetpilot says, it's not pads. When pads fade the pedal stays hard but it just doesn't pull up, when it's fluid related, it goes spongy, or even to the floor.

Firstly bleed your brakes with some decent fluid like the Motul RBF600 and consider using 2 bottles to make sure it's a good bleed.

If that doesn't work/help then you need to look at the next stage which is lines, replace with braided and again bleed well and all should be good. If this fails then I guess the seals in the calipers are rooted and need replacing but I would suspect the lines before the calipers myself.

[blind_elk]

Another point - did you actually drain the old fluid completely out of the system. If not, then you still have crap fluid present.

Jack both ends of the car, and just open the bleed nipples. When the master reservoir is empty, fill with your new (Dot 5) fluid. When it appears at the bleed nipples, shut them off. Then bleed as per normal bleed procedure.

[djr81]

Can I just recommend the following:

DO NOT USE DOT 5 FLUID

It is horrible, non compatible stuff that should stay on the shelf at the shop where it is offered.

If you use the dot 4 - 600 fluid you will get better pedal feel whilst having a HIGHER boiling point for the fluid.

Dot 5 is not better than dot 4 just because it has a higher number. It is, IMHO, rubbish that should not be used on any Skyline.

[sky30]

Yeah i completely drained the old fluid before adding new stuff. Peadal feels good and brakes seem to be good when cold, its only when i brake continuosly/ excessive that they have the problem.

Looks like i will try better fluid.

Anyone had any trouble with the std ABS unit?

Are people with factory ABS still using it, or have removed it?

[djr81]

Yeah i completely drained the old fluid before adding new stuff. Peadal feels good and brakes seem to be good when cold, its only when i brake continuosly/ excessive that they have the problem.

Looks like i will try better fluid.

Anyone had any trouble with the std ABS unit?

Are people with factory ABS still using it, or have removed it?

Some people remove the ABS others not. It is heavy, slow cycling & to be honest not the greatest unit ever built. But it is better than nothing.

If after heating up the brakes go away either your pad compound is not up to snuff or other components (less likely) are suffering (eg rubber brake lines).

[sky30]

Some people remove the ABS others not. It is heavy, slow cycling & to be honest not the greatest unit ever built. But it is better than nothing.

If after heating up the brakes go away either your pad compound is not up to snuff or other components (less likely) are suffering (eg rubber brake lines).

Pedal definately goes spongy and nearly to the floor when thngs heat up.

[djr81]

Well if you are satisfied you have removed the pads & the fluid as a source of the problem the next step is the rubber hoses next to the callipers, the master cylinder & then the callipers themselves. In that order.

But I would still make doubly sure it isn't fluid related.

[gslrallysport]

Pedal definately goes spongy and nearly to the floor when thngs heat up.

Fluid... nothing else.

[Evil34]

Hey Andrew,

Replace the lines with braided lines and fill with RBF600 or a really good dot5 and you will notice a massive difference.

You could also look at a master cylinder stopper which would help trying to pull up you 400+kws.

If that fails to work then you have to be looking at bigger brakes!!!!

[GTAAAH]

This sort of saves me making another thread, so i'll semi- hijack yours

I have a gtr with standard rotors, (well standard spec, not slotted or anything tho) and some high performance pad (i saw them in a catalogue and they're quite exxy green ones)

Anyways after doing a few spur run's i locked up the brakes a lil coming into a corner and had the abs light come on, it braked fine but about 10 minutes later when i stopped at some lights i could push my pedal all the way to the floor, and pumping didn't really work. By the time i had gotten home the problem had almost gone and now when i drive it it brakes fine but it doesn't seem as responsive.

More effort is needed to brake (it still brakes easily enough) and my corolla and val both brake alot easier than the gtr. I can't really remember how it was before you but considering the size of the brakes i'm guessing they're normally alot more responsive.

It has plenty of fluid and i only bled the brakes about 1500 km's ago, i'm thinking maybe the diaphragm is gone but i'm not sure, maybe gtr's have a bit of take up b4 they break standard.

Also 1 other thing, idk if it's bad but it never happened in my old car, my brakes smoke a fair bit after a hard-ish run, they don't smell oddly enough at all but they smoke a fair bit

Ne ways, no idea about the 2nd bit but does the 1st problem sound like master cylinder is shot?

Edited December 19, 2007 by GTAAAH