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Rear Brakes Locking up on hard braking.

Cubes

By Cubes,
in General Maintenance

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Cubes Grand Master

Cubes

Posted
Posted

Just before I slapped the new brakes in I done one hard stop and noticed just before I stopped the rear brakes locked slightly.

Now that I have Both Ultimates in the front and rear (Before only in the front) when I hit the brakes I get the back brakes locking up. They arn't really easy to lock up but in an emergency (over 80km's) it can be very dangerous.

They are also very dangerous if you hit the brakes around the corner.. Massive Oversteer.

Next week I'm going to get it checked out but this weekend I am going to try a fluid flush and see how it goes.

Any Idea's Suggestions?

Possible Mastercyclinder is passing fluid though the pistion? or has the R32's got a rear front reg?

Merli Grand Master

Merli

Posted
Posted

You should never be braking through a corner anyway. Do your braking before you arrive at the corner.

In regards to your problem, if your back brakes are locking up before your fronts, you have a massive bias problem. I would assume that you have a pinched line somewhere affecting this bias.

PranK Grand Master

PranK

Posted
Posted
Originally posted by Merli

You should never be braking through a corner anyway. Do your braking before you arrive at the corner.

believe it or not, on public roads there will be some circumstances that will cause you to brake during a corner!

Joel, i would stop driving it until you get it looked at, or at least drive it slowly.

GTR King Collaborator

GTR King

Posted
Posted

One thing that could cause that is sticky caliper pistons in the front. Suggest rekiting the front calipers , machine all 4 disks and put new disc pads all round of the same type and compound. If it is rear wheel drive only i would suggest u check the front dis hub seals as well and replace if needed. I would suggest BENDIX standard. They can take a good beating but wont be as hardy as Metal pads. Keep in mind if u drive realy hard for long period eg Exessive heavy braking for constant periods over short distances, and i mean realy realy thrashing it , they can fade slighty but personaly u can get away with standards easly, they can still take a fairly good beating. If u have brake ducting installed it shouldnt be a problem.For 100$ -120$ worth of pads i would give then ago first im sure u will be pleased and it would pull up fast and straight every time no rear whell lockup BS. It is ABSOLUTLY ESSENTIAL u machine the discs and do it propperly. Metal pads dont pull up as good either and also will chew your rotors out faster therefor costing u lots more $$$ in the long run. Personaly ide rather be changing pads that rotors every brake service. My advice put same pads all round and machine all 4 discs prob cost around 350-400$ all up dont quote me on that but better to be safe than sorry. If u rekit the front calipers it would prob cost another $200 around that figure, but i would try the pads and machine work first, thats what i would be doing anyway.http://www.bendix.com.au/_products.asp

BTW asbestos will not be in any pads soon by law so if u can get hold of some BENDIX standard pads Joel i would buy a few sets as they will be rare as hens teeth soon. I always use bendix standard in all my cars no prb ever. the mechinc workshop i worked in thats all we ever found were and good from fleet cars to high performance. Also will help aviod brake sqeels. Its your descision in the long run but thats what i would do no ifs or buts. Saftey first then performance.

Cubes Grand Master

Cubes

Posted
  • Author
Posted

I have recently only just done a bran new set of disks and bendix ultimates all round.

All callipers pushed in with the bleed nipple open by hand.

I have had really bad experience with the Std brake pads.

On my previous car a VS 5ltr Manual Commodore with ABS i did a few hard brakes from approx 100km/h and on the 4th brake I had no brakes. Also I would do 180km/h and by the time I hit around 60km/h the brakes would be really hard to push hence fading. Then again it is Commodore Family brakes we are talking about :) Single Piston..

I've always run a minimum of metals but the ultimates are a bit nicer on disks than the metals so that is why i chose them.

Just before I replaced the rear brakes when i had already done the fronts i noticed on a hard brake just before i stopped the arse end would lock.

I slapped the new pads in and it was really really bad but i do remember when i first slapped the fronts on the ultimates were really grabby but they calmed down over a day or so.

I have a gut feeling it is the Brake Mastercyclinder as 3 previous cars inc. the Mazda 626 I still have both had the same on set of problems.. Rear brakes locking up then all of a sudden the pedal one day would be around 10cm's from the floor and you would loose your rear brakes.

I really do think it is the mastercyclinder.. I will find out monday. :)

I will keep you posted so that you know and every one else what the symptoms of a buggered mastercyclinder.

Previous cars that i've had exactly the same onset of problems are:

TE 250 Cortina.

1300 Corolla

Mazda 626..

I'm hoping it is somthing as simple as brake bias but i wasn't sure if that was controlled by a seperate valve unit on the R32's or the Mastercyclinder its self.

Really I have to slap it over the pit and have a look......

Any one know if the Mastercyclinder is the same as the 300ZX Z32 as the rest of the brakes are..????!?!?!

They don't actually make Std. Bendix for the 300zx/GTS-T's.

Cubes Grand Master

Cubes

Posted
  • Author
Posted

On that note of std pads when i took the vs in to get the rear chassis repaired down at Bridgestone at Noarlunga he noticed that i had std pads on.. He said that they came out with metals and if i were to take it over the pits and they noticed i could get defected.?!?!?!

GTR King Collaborator

GTR King

Posted
Posted

Well then alot of mechanics would get into trouble wouldnt they ?

If u r not towing a caravan it wont matter and how the hell would they even know they all lok the same and they wont strip your brakes to look at them. Dont worry about that if u want them fit them i would if it was my car , bugger what other ppl say. If u r not sure and r a goddy 2 shoes hehe ring the RTA and ask em if its legal. But as if i would carfe about that, i use what works for me.

Cubes Grand Master

Cubes

Posted
  • Author
Posted

Bendix Don't actually make the Std Pads for the Skylines/300ZX's.

The only pads listed are the Metal King Plus and the Ultimates.

If i could it would be cheaper for the next couple of years while i'm at uni...

Some ppl are funny if you get my drift.. :)

400HP Experienced

400HP

Posted
Posted

Let me know what happens. I have a similar kind of problem although not as extreme. When I press the pedal... for a very split second the brakes making a *clunk* noise where no actual brake pressure is applied... then the brakes come on very hard. I'm not sure what it is either so let me know what happens to yours.

Cheers

Cubes Grand Master

Cubes

Posted
  • Author
Posted

Will Do.

Mine actually arn't that bad they only lock up a fraction of a second before you stop, but around a corner it is dangerous.

So when you say clunk is the clunk from the brake pedal/power booster or from the brakes calipers.

My powerbooster makes a type of clunk/click noise when applying the brakes hard or if you sit stationary and press the pedal hard. You can also feel the clunk through the pedal.

Same??

400HP Experienced

400HP

Posted
Posted

The clunking noise seems to be coming from the rear brakes. And I can only really hear it at lower speeds.

I only changed my rear brakes about 2 months or so ago (leaving the fronts) and no discs have been machined. I thought it could be something I've done when I changed the pad. I removed the shims but I doubt this has anythig to do with it as I've spoken to quite a few workshops about this and they say its fine. I've been to wakefield and driven hard a few times since and its not so bad that its not driveable...

Mine are like yours.... I think they lock for a tiniest fraction of a second. Barely noticeable.... as i said the noise is coming from the brakes... I don't notice any noise from the actual pedal.

I think even if its not the same problem it could be similar. When I changed my pads I also did what you did... I pushed the calipers in by hand with the bleed nipple open...

very strange..

GTR King Collaborator

GTR King

Posted
Posted

Clunking can be worn suspension bushed mainly, also check that u have the anti rattle springs fitted to the calipers if they have them standard. BTW Joel i suggest same disc pads all round not standards in the back and Ultimates up front. Im not realy farmiliar with skyline rear suspension but more than likely its the radius rod bashes witch stop the wheel moving bakwards and forwards ander acceleration and braking.

Cubes Grand Master

Cubes

Posted
  • Author
Posted

400HP..

Why did you remove the anti-squeel shims?

They are there to absorb vibrations etc..

They can be removed and wont cause problems but have you tried slapping them back in to see if it makes a difference?

did you remove any other shims that are placed around the caliper?

I think after you pull the two pins out there are two shims on both sides of the calliper where the edges of the pad touch.

I wouldn't think machining the disks would make any difference to clunking unless they had a lip on the edge and the pads grabs that.

lol.. Checked your wheel nuts?

Slap the shims back in and see.. Pads are easy enough to pull out.. 2 pins and they slide out the back of the calliper :)

It takes longer to pull the wheel off :)

Cubes Grand Master

Cubes

Posted
  • Author
Posted

Yer there definately two shims that sit around the edge on the inside of the calliper but..

They are hard to see if they have brake dust, have a look see :)

well thanx ppls for you help...

Car will be looked at tomorrow.. :)

I'll keep you posted.

Cubes Grand Master

Cubes

Posted
  • Author
Posted

I did a full brake fluid flush.

Since I bought the car I've done all up 3 fluid flushes now.

When I first bought it, the fluid was clean then within a few weeks the fluid was dirty with a type of black gunk around the edge of the resivour. There were also little bits of the black gunk in the fluid floating around.

Flushed all good then next time the stuff was back again but not as bad.

This time the fluid was black again?!?! WTF...

Anyway I flushed it good and proper by getting the other half in the car pushing on the pedal as i opened to bleed nipple then holding the pedal down while i did it back up again.

Eventually after 1/2 bottles all the fluid was clear again.

Jumped in the car and well the rear brakes would not lock up but the right front would.

Drove a little more the right front stopped locking and both would lock at the same time..

Then a little more driving, hardish driving and yep well the rears started to overbrake again.

If i feed the brakes on harder and harder then the rears will eventually lock but you have to press damn hard.

If i jump on the pedal hard then the front will lock, if i jump on the pedal semi-hard then all 4 will lock.

This black crap that is in the brake fluid has got me stuffed.

I think the previous owners possibly didn't change the brake fluid ever.

OR.. I don't know...

I checked all of the brake lines (rubber) while i was there. Non-perrished no leaks in the pistion rubbers either..?!?!?

GTR King Collaborator

GTR King

Posted
Posted

When it comes to brakes better to be safe than sorry i say.

Personaly i would at least rekit the brake calipers and check that the flexible lines look in Good condition. Also use a better qaulity brake fluid after that so it raises the boiling point but most PBR fluids are pretty good anyway. If u dont wanna spend hell cash and havnt done it before i might give u hand to do it as i have done many before. Its not real hard just ime consuming. If u r interested let me know.BTW have u ever seen these new rotors they rox0r http://www.dba.com.au/brakerotors.asp

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