Ford Scorpio Forum - Print Page


    
      
        Ford Scorpio Forum
        (https://www.fordscorpio.co.uk/cgi-bin/yabb/YaBB.pl)
      

        General >> Problems >> Un-balanced front brakes
        
(Message started by: johnv on Feb 25^th, 2005, 11:03pm)

Title: Un-balanced front brakes
Post by johnv on Feb 25^th, 2005, 11:03pm

Well my 1998 cosworth done 68,000 miles failed its MOT today on un-blanced front brakes.
I looked at the brake lining and steel discs. all OK.
I never get any of that juddering that you get upon braking with distrorted brake discs.
I don't normally use the brakes, at least very little. but i done a few straight ahead stops on private ground, with my hands just off the wheel and the car stops dead straight. no sign of pulling to one side.
I not going to mess around myself so I going to book it in at this small non ford garage I using now.
Just wondered if anyone had similar problem. It surely can't be calipers sticking, the wheel turn around with no sign of rubbing.
Just trying to get some inflo, so that I don't appear to be a complete dummy when I take the car in.
Thanks to anyone that can help.

Title: Re: Un-balanced front brakes
Post by Baz on Feb 25^th, 2005, 11:12pm

unbalanced brakes? Thats a new one on me John ???

Mind you, my Cosworth with 67000 miles has had new disks and pads all round last year when I bought the car on 58000 miles.

Title: Re: Un-balanced front brakes
Post by johnv on Feb 25^th, 2005, 11:14pm

well they are saying that the reading on one side is different from the other side.
But I going to watch them like a hawk on this.
On the road the car just brakes so nice, as indeed all these scorpio's do that have the 225 wide tyres on.

Title: Re: Un-balanced front brakes
Post by johnv on Feb 25^th, 2005, 11:19pm

all this renewing of steel brake discs on car that have done only 30,000 or a bit more bugs me.
I thinking it got to be down to mad driving, using the brakes very hard constantly. thereby overheating them or the like.
If I could have afforded a brand new scorpio, the way I drive, the steel brake discs would have lasted the life of the car.

Title: Re: Un-balanced front brakes
Post by Geoff_W on Feb 26^th, 2005, 12:30am

John,

Bad news, sorry to hear it.

I think Scorpio disks were a bit prone to warping, however some of the smaller engine variants use the same part as four stud Mondeos on the front which I believe are a much lighter car.

Maybe thats part of the problem.

With mine I have got in the habit of asking for a price for disks based on a 2 litre Mondeo.

When they give me that I ask for the same for the Scorpio.

When they come up with an aftermarket price 15 or 20% higher I get them to compare the part numbers. Lovely to see their faces.

Geoff

Title: Re: Un-balanced front brakes
Post by mr._floppy on Feb 26^th, 2005, 12:52am

I wonder if the high rate of deterioration of front brake discs is due to the lack of a splash guard .The rear discs have one.

As to the MOT failure, the rolling road brake test is there to detect poor or uneven stopping power, and is very sensitive.

My old car was failed on poor handbrake performance.

Title: Re: Un-balanced front brakes
Post by Eddie on Feb 26^th, 2005, 5:25am

One possibility is different pads on each side,differing friction rates etc.Try new pads both sides.
Other possibility is air in one of the calipers.
While your at it pop some SILICONE brake grease under the rubber piston covers BEFORE pushing the pistons back.

In case you are not aware,the REAR brake pistons have to be WOUND back in and not just pushed back.
(I know you were talking FRONT,just slipped that in for info)

eddie

Title: Re: Un-balanced front brakes
Post by johnv on Feb 26^th, 2005, 6:25am

thanks to all for advice. at my time of life i leave it to garages to sort my problems.
I've done printouts and will make sure the garage know about anything I feel they should know.
thanks again to all, and yes i soon as i know what the trouble was i will post it here so that's others can benifit if they have similar problems.

Title: Re: Un-balanced front brakes
Post by johnv on Feb 26^th, 2005, 6:29am

I wonder if the high rate of deterioration of front brake discs is due to the lack of a splash guard .The rear discs have one.
------------------------------------------------------------------
Well, indeed I seem these scorpio's, where the rim all around the outsides of brake discs, have been crusty rusty with bits flaking off.

Title: Re: Un-balanced front brakes
Post by Paul B on Feb 26^th, 2005, 9:12am

The MOT brake balance thing is a proper part of the test.

Each of the wheels is tested individually and the difference between them calculated as a percentage. If that percentage is above the limit (can't remember what it is off-hand) you fail >:(

I know this because my old Cortina had trouble with this part of the test in the past. The problem there was lack of use and the calipers would stick like crazy. In the end, I removed them both, stripped them down and rebuilt. Worked fine after that and still do.

John, I've got a feeling your problem could be the same, especially if its one of your 'spare cars'. I just hope the garage you're giving it to are OK, because I think many would see sticking calipers and just tell you that you need new ones. All just 'fitters' these days.

Title: Re: Un-balanced front brakes
Post by johnv on Feb 26^th, 2005, 11:40am

thanks to paul B, yes i was thinking this about sticking cylinders. but it make the position so much more clear. to hear it discussed with others
I do know that this car had not had much use as the last owner had other vehicles, and the reason why he decided to sell it with regret, was because it just stood there.
I will tell the garage to look for sticking cylinders, at 68,000 mile I not going to go into new calipers. I thinking.
I got to ask them how much their charges will be to strip the units down and rebuild against new units.
If their charges for labour mean I might as well have new units, I will ask for the old unit to be returned to me and I can overhaul that myself on the bench and keep as a spare.
It might be that if I am lucky, that just pushing in the cylinder and pushing it out again a few times might free it off.
But thankyou for your advice, its real great to have something to be armed with to counter any attempts to occur me in any higher costs that is not needed.

Title: Re: Un-balanced front brakes
Post by zygoteer on Feb 26^th, 2005, 12:08pm

Many (too many) years ago I was part of a team that designed a (then) new commercial Brake Tester, and electronically there were a few basic parameters than can concievably cause a reject for 'unbalanced' etc. (depending on the reject thresholds setup) that can be selectively analysed via a multiple load-cell array output.
tractive effort characteristics (braking efforts etc)
run-out/ovality
grab/release latency (lag)
bearing oscillation/condition
lateral imbalances(tyre inconsistencies)

I think there were a couple of other things too, but I can't recall clearly now (hmmm ... I don't remember being absent-minded lately either)

The point is that, like a lot of things, there is more than one possible 'failure-mode'.

I can never come to terms with most peoples obsession that a problem will only have one cause, which they insist on knowing what it is, as if they either understand or could do anything about it (if they did and could - they wouldnt ask the question - so they got no chance).

OK, thats about it, and I am now starting to sound like Victor Meldrew, so I best shut up

Title: Re: Un-balanced front brakes
Post by johnv on Feb 26^th, 2005, 1:12pm

God almight Zygoteer, you certainly know how to do my head in.
Hey, can you do that posting again, but this time in English?
lateral imbalances(tyre inconsistencies
I thinking of putting two spare wheels on the front that I have as spares in my out house which have brand spanking new tyres on.
Do you think that if I took the car to a different testing station that their equipment might be set up different and i might receive a pass om this un-balance or so they say.
run-out/ovality So it could be the discs that are out dispite the fact that they don't judder or anything when braking.
bearing oscillation/condition . so the bearings could be about to blow up.
well thanks for the advice, i doing prints outs and will be well armed with knowledge to let the garage know i not to be messed with. (even if it is mostly bluff.)

Title: Re: Un-balanced front brakes
Post by zygoteer on Feb 27^th, 2005, 12:02am

I didn't say you have all or any of theses issues, just that there is often more than one cause etc.

It is true though that a low-speed rolling road (usually between 2 and 6 mph) can be set up with torque, weight, skew rotation load cells such that analysis using multi-point fast-fourier transforms on the compounded data can yeild some pretty compelling evidence of a fault or faults.

This is probably a boring topic for others, but If you want me to expound further just for you, then let me know.

Title: Re: Un-balanced front brakes
Post by johnv on Feb 27^th, 2005, 8:06am

Hey Zytozeer,
You will know this.
In the past I had two chaps jumping up amd down on the rear tow-bar/step on my transit vans,when on rolling road.
I when straight away to tell them to get my van off the rolling road and back outside.
Then
I then drove off leaving three chaps there with their mouths open.
That was at Halfords, before I knew what they where like.
So I went to another testing station down the road where the van passed its MOT without two chaps jumping up and down like monkeys,
I mean I did not want my step bent or something like.
God they where loving it jumping up and down and the van was bouncing up and down as well.

Title: Re: Un-balanced front brakes
Post by zygoteer on Feb 27^th, 2005, 12:20pm

Whislt on a rolling road, extraneous influences (jumping up and down on the back for instance !) are bound to affect the data coming from the equipment, so any conclusion on the vehicle condition will be influenced ... either positvely or negatively (impossible to say unless the influencing is precisely defined).

I stopped taking my vehicles to garages a long long time ago for the kind of reason you describe, except for MOT and maybe tyres/exhaust replacements (even then I always checked their work before, during and after - many times having to correct things).
Also their complete lack of respect for other peoples property I find disturbing.

Maybe I am just too fussy ... oh well

Title: Re: Un-balanced front brakes
Post by johnv on Feb 27^th, 2005, 1:02pm

Also their complete lack of respect for other peoples property I find disturbing.
---------------------------------------------------------------------
Hey zygoteer,
We speak the same lanuage. You got that spot on, its just like is if I was writing that.
(but don't mention the word insurance, or you will be in the dog house like me).
I think that case of those two jumping up and down on the back of my van was because it was raining outside and they where trying to get more grip.
But wait, I been for lots of tests in the rain and nether had that done before.

Title: Re: Un-balanced front brakes
Post by johnv on Feb 27^th, 2005, 1:16pm

hi to zygoteer.
When I used to be in business, I had two top fitters who worked for the Council look after my vans until they moved on to better paid top jobs.
One moved to near Manchester Police looking after the Granda's that bombed up and down the M6 and the other one got a job with AP. in Leamington Spa. Warwickshire.
Automotive Products, they make lots of things but brakes they are hot on.
He was based at the old RAF Airfield at Gaydon. (that where i was for 5 years with the "V" bomber force).
They use to make and try out new bits and peices and design new brakes and all that stuff.
If only I had these chaps looking after my scorpios now.
I remember one of them had a grandna and his little box of tricks (Computer I think) when wrong and he did it himself in a jiffy. I remember him moaning about the cost of the part being £380 as it was then.

Title: Re: Un-balanced front brakes
Post by johnv on Feb 27^th, 2005, 2:59pm

hi zygoteer.
just to say that before I let the garage mess with the brakes i going to ask them to put it on the rolling road again to see if it is ok now.
The reason, one front tyre is an Avon ZZ1 and the other tyre is a Avon ZZ3
So whats the difference. I don't know they look the same.
But about difference compounds, i thinking, surely that would not be enough. but any way, it worth for what it takes to just put it on the rolling road.
I also been using it alot and stamping on the brakes when I on my own to see if that does anything.
Since the last owner had it parked up a lot and not used , I still got it in the back of my mind, that it might be just sticking pistons.
But time will tell.
Thanks for yours and others help

Title: Re: Un-balanced front brakes
Post by zygoteer on Feb 27^th, 2005, 4:01pm

Sticking pistons are usually shown up in the tester electronics as grab/release latency, sometimes called lag-on/lag-off.

A lot of brake test equipment I know of (not a definitive knowledge base nowadays you realise!) has the capability to diagnose which wheel and in the case of drum brakes sometimes which piston (upper or lower) WITHOUT DIS-ASSEMBLY, but either :
1. the garage wasn't prepared to pay for the option being enabled on ordering the kit
or
2. the operator is simply too stupid to know how to use it (was asleep/drunk during training & can't/won't read manual)
or
3. they deliberately don't tell you as that would be an income generating opportunity missed ! (separate billable job etc.)

I can remember a time when they simply volunteered this info for the cutomer, but you choose the excuse for the present :D

Title: Re: Un-balanced front brakes
Post by martin_rowe on Feb 28^th, 2005, 9:11am

the MOT brake test is quite a simple thing with no grey areas, only pass or fail.
if the test showes that your car has exceeded the 50% efficientcy for the foot brake and 16% for the park brake (in the case of a scorpio)it will pass, brake out of ballance is another thing, both your front wheels will be tested at the same time, with the tester slowly applying the brake to a point just before a wheel locks, he will note the differance in readings between the two wheels, if this reading varies by more than 25% the brakes will fail, thats quite a big differance and allows for minor differances in tyres and tyre pressures. if the out of ballance is less than 25% you should have a pass.
if you have such a large brake imbalance you would certainly notice it under normal driving conditions, more so under heavey brakeing. if you have any concerns at all ask to observe the brake test.
that was only a simplified explanation of the brake test, the test procedure actually takes 30 pages to explain in the test manual.
martin
martin

Title: Re: Un-balanced front brakes
Post by johnv on Feb 28^th, 2005, 1:23pm

if you have such a large brake imbalance you would certainly notice it under normal driving conditions, more so under heavey brakeing. if you have any concerns at all ask to observe the brake test.
---------------------------------------------------------------------
Thanks to Martin_Rowe for that.
That's what.s i got on my mind.
I tried it out on a level road, braking hard, with my hands just off the wheel and the car stops very quick indeed. (to quick for my liken)
Does not twitch a bit on the steering. stops dead straight ahead, and not one wheel leaving a black mark on the road.
I done the same test, this time with my hands on the wheel to see if I can feel anything through the steering wheel.
I also jacked up car and spun the wheels to see if one wheel is draging, but no, both spin free.
As soon as I get the new safey belt from ford parts i will fit that and then take the car back for further looking at.
But again thanking people for their help, you have been real great.
And I promise not to leave any more postings on insurance. ;D
Mind you, I could never keep promises. :D
Hey just wait a minute. :'(
That's done it my "Which" magizine just throught the letterbox.
It's all about AXA Insurance refusing to pay out and them being reported to the Financial Ombudsman, who told AXA to pay up and pay heavy compensation.
It says POINTS OF LAW.
If an insurance company is in breach of contract, or refuses to deal with a claim, you can make a complaint against it to the Financial Ombudsman, who can award compensation for inconvenience and stress.
Still promised not to do any more postings on insurance so I can't say about it. ::)
Well it was like this. See this insurance company, . hang about, just look at the time, sorry I got to go. Bye. :-X

Title: Re: Un-balanced front brakes
Post by bazw on Mar 2^nd, 2005, 1:07pm

john hi
the normal reasons for unbalance are
1: the caliper on the low side is stuck on its slide pins so that only the piston moves this pushes 1 pad onto the disc and the outer will not move untill the piston bends the disc out onto the outer pad (a quick check is to have some one push the brake s on when cold so you dont burn yourself ,and feel the calipers through the wheels if it moves then discount )
2: the piston is not getting full movement because of corrosion on it so it sticks and will not opperate the caliper fully
3: the pads have rusted where they sit in the caliper and cannot move so giving a false feel (sorry cant think of a better way to put that at the mo ha ha ) to fiz take out and clean the ends (they look like a thick "T")with a wire brush
i would check them in that order as thats the order you take them to bits :)

if you have a stuck caliper ,piston or pads you may see that the outer pad is not worn as much as the inner