Technical Brakes again...

[The Panda Nut]

Why I wonder is it that all brakes seem to **** up after just a few months. Years ago I used to put pads in, and after 20K miles replace them and the discs although worn would be polished clean on both sides, now after just a few weeks the back sides of the discs rust and the the pads wear away as the rust is harder and rougher than the disc. These brakes are in perfect working order with free slide of the caliper and smooth operation of the cylinder and they have been stripped and cleaned, had the lips removed, checked for uneven wear and runout just 8 months back, and yet they look like something thats been parked in the sea for 5 years. Does this pisss me off big time?? You can bet it does. From the wear lip its pretty clear that its being driven italian style by my youngest. Does asbestos free have to mean totally @@**{{** useless? Surely somewhere out there there is some materials that dont do this. On the up side the Blueprint discs look superb and incidentally are at least 10mm bigger diameter than the ones just removed. Maybe there is the answer right there? Someone fitted rubbish parts last time. The other 1.2 however seems not a lot less bad. I suppose I should check the newest car too.... I really dont feel up to this, AND I have much better thing to do anyway. As far as I can tell it was the pads that were cutting their way through the disc too!

 

[koalar]

too many variables

aggressive pad material like greenstuff will wear out disc at about the same time as the pads

with standard pads you get around 5x as many pads to discs

How you drive, two track days and discs and pads will be shot

most pads these days come with an aggressive coating to clean up the discs. You are suppose to drive them carefully for the First 200 miles

I get over 100,000 miles out of Panda discs, but it is possible to trash them in a few weeks.

 

[DaveMcT]

A pair of Mintex solid discs for Panda front brakes cost £25. But your third image is the result of poor maintenance. Sticking caliper slides will not allow both pads to grip and release so the disc surface gets pitted with rust. Ultra careful driving actually needs at least as much (if not more) brake maintenance than driving with lead foot.

 

[Pugglt Auld Jock]

But your third image is the result of poor maintenance. Sticking caliper slides will not allow both pads to grip and release so the disc surface gets pitted with rust.

Not sure I agree with you Dave. Yes poor or non existent maintenance can lead to all of that, especially when the caliper slides or actual pistons themselves are not free moving - many people do not appreciate that caliper pistons need to be free in their bores because its the rubber seal which retracts the piston. What? I hear the cry goes up. Well, when you stand on the brake pedal of course the fluid is forced, by the master cylinder, down the brake pipes and into the caliper. The caliper is a closed vessel with a moving piston surrounded by an O ring which stops the fluid leaking out past the piston. What people don't generally appreciate is that once the piston has moved the pads into contact with the disc then further pressure on the pedal will cause the rubber seal to distort slightly as it tries to squeeze past the piston. It's retained in the cylinder wall by the fact it sits in a groove so it can't really "go" anywhere there but the side of the piston is smooth so the seal distorts and slides outwards very slightly (you can get upwards of 1,000 psi in a typical heavy braking situation). As the pressure reduces when you lift your foot off the pedal and pressures equalize, the seal will return to it's normal shape and this will cause the piston to retract very slightly into the cylinder due to the seal gripping the piston as it regains it's resting shape. This is just enough to give virtually no drag between the pads and disc but you'll find it very hard to actually see any gap. If the piston and/or cylinder is corroded it will not allow the small force the seal can exert to withdraw the piston so the pad/pads will drag on the disc. "Sticky" sliders will have similar consequences - so in that respect I'm in agreement with you.

However, back to that third picture and what I disagree with you about. I'm not at all surprised to see this. I've done many brake rebuilds in my time and the pictures shown here look pretty standard for a vehicle which has not actually been excessively "pampered". The outer facing side of the disc, being protected by the wheel, can look quite acceptable whilst the inner, being much more open to all the salt and road dirt, corrodes just as these pictures show. Can I say to all of you with these "fancy" alloy wheels that are so common these days, and with very "open! spoked type designs. It's very tempting to asses your brake condition simply by looking through the spokes at the nice shiny outer disc face - Beware though, you might get a nasty shock if you get down on your hands and knees and take a look at the inner face! That disc shown in the 1st and 3rd pictures with it's scored and lipped, but smooth outer face and it's heavily rusted inner surface with only about half, maybe, of the surface providing effective braking definitely is fit for scrap only but I've seen many many in that condition with the caliper still perfectly serviceable

 

[koalar]

looks more like firescale in my opinion, Its quit easy to overheat the brakes and even set fire to cheap pads

 

[Pugglt Auld Jock]

looks more like firescale in my opinion, Its quit easy to overheat the brakes and even set fire to cheap pads

View attachment 407231

Aye, there are similarities - it chips off quite easily for a start, but it's just corrosion. My own "pet" theory is that the inner face rusts so much more because it's open to the dirt, salt and water from the road but, being tucked away as it is, stays damp for much longer than the outer face which is anyway being kept much cleaner and dryer due to the wheel. Even a spoked alloy wheel is going to deflect a lot of rubbish due to it's rotation and even though not protecting like a steelie would, it's open to air and wind so moisture can evaporate readily.

For people interested in Panda front brakes this post I made back in early 2018 might be of interest: https://www.fiatforum.com/threads/beckys-brakes-a-few-surprises.459983/ I'm not for a moment suggesting that Panda Nut's disc would clean up in this way, it's very obviously worn out, but the problems I had and some of the procedures and products I used might be of general interest?

 

[koalar]

is it cracked ?
photo 3
12 o'clock

could just be the way its photo'd

 

[Pugglt Auld Jock]

is it cracked ?
photo 3
12 o'clock

could just be the way its photo'd

Hmm. Difficult to say without running a finger nail over it or giving it a sharp tap to see how it "rings" - or not. I think it's maybe more likely to be a pad "resting" mark though. Could be another at about 2.30 to 3.00 o'clock?

 

[koalar]

I'd be keen to investigate further

needs a mic or callipers to measure the thickness

I don't think there's enough metal mass left to take the heat away they start at 10.9 mm with a minimum of 9.2mm Which is under a mm wear per side. To thin and they will overheat much too easier

A lot can be told by looking at pads. They should all have roughly the same amount of even wear, (no wedging) left and right sides should be identical.

I fell like want the parts in my hands.

 

[Pugglt Auld Jock]

I'd be keen to investigate further

needs a mic or callipers to measure the thickness

I don't think there's enough metal mass left to take the heat away they start at 10.9 mm with a minimum of 9.2mm Which is under a mm wear per side. To thin and they will overheat much too easier

A lot can be told by looking at pads. They should all have roughly the same amount of even wear, (no wedging) left and right sides should be identical.

I fell like want the parts in my hands.

Yup. In my opinion those discs and the pads that were running with them are "toast" - fit for the bin only. "I feel like I want the parts in my hands" is how I often feel when making a post on the forum - it can be so difficult trying to diagnose a problem or give targeted advice from afar.

 

[The Panda Nut]

A pair of Mintex solid discs for Panda front brakes cost £25. But your third image is the result of poor maintenance. Sticking caliper slides will not allow both pads to grip and release so the disc surface gets pitted with rust. Ultra careful driving actually needs at least as much (if not more) brake maintenance than driving with lead foot.

No vehicle of mine is pooly maintained! All are maintained more regulariy than required and to the highest possible standard irrespective of cost. I think I said the sliders are and were all completely free and the pads ends where they slide all detail cleaned, wire bushed repainted and put back, as were the discs less than 8 months back having been cleaned de rusted and having the lips removed followed by being checked for run out and thickness measured at almost 100% of wear. They were also repainted but have corroded so much in the 32 odd weeks since that there is little trace of the VHT black used, I can state without a shadow of doubt that there are no better maintained cars anywhere. Had I not done this myself I might well have thought and commented as you have. My vehicles have the wheels removed several times a year and these are clay blocked and polished inside and out. I was intending to do this not the brakes. I suspect the discs and pads (put on by Inchcape Toyota before we bought it) are something like ECP or similar. I thoroughly object to throwing away discs and pads where the disc are still well above the limit and the pads half worn. The car may be 11 years old but these parts are only 4 years old having covered only around 30K miles! On a Panda this is poor. We shall see how coated top quality german discs hold up. Personally I dont expect to be dismantling such things at 6 month intervals just to maintain safe brakes, Some of these cheap parts need taking off the market I think.

 

[The Panda Nut]

On this car the new Bilstein discs fitted were 12.5 thick and the min tolerance stamped ion the disc is 9.8 The new discs are both bigger diameter and thicker than the old ones to such an extent I am actually wondering what exactly it was running on. The last occasion is went to the dealer was because of a fluid level sensor failure so it had this done and a full brake service back and front, that was about 18 months back. The pads appear to have a hard metal lump in which appears to be the cause of the deep groove cut in 1 disc. My point is I suppose that this is not a 1 off it seems to be common to find the pad material being pushed off the backing plates by rust after 2 years and calipers failing to slide for no apparrent reason also seems common. I shall obtain new caliper / pad retaining pins asap as it does occur that these may be adversly affecting caliper sliding if corroded. As usual i did clean them with wire brush on the drill and fine emery but as the pads wear they also act as slides. My assumption is that the sort of force applied would be sufficient to prevent such things having a material effect in normal circumstances. The pads were still free and the aluminium based anti seize seemd to have done its job well. I cannot remember the last time I looke dat braked and found both sides of the discs looking normal on any car. I did check these discs after 3 months or do of use and all appeared to be well finding them in this state was a shock. Quite good enough to pass an MOT though! If it in balance that seems to be good enough. It beats me what use such a test is if this got through as in my book, as you say the whole lot was a bin job.

 

[koalar]

are you sure its not just the way it been driven ?

you can trash a set of disc and pads in a few weeks with a few heavy stop per day. I killed a set in a few weeks going from 90+ to 20 4x a day in my youth when they put roadworks ramps on a fast road. When it started to cost me money I soon slowed down

Still looks more like firescale to me, would fit with all the paint burning off

 

[koalar]

I get over 100,000 miles out of ECP discs and pads

I do drive especially carefully for the First 200 miles or so

so no it not all discs and pads that die after 20,000 miles

Cheshire flat, few hills which helps

 

[The Panda Nut]

are you sure its not just the way it been driven ?

you can trash a set of disc and pads in a few weeks with a few heavy stop per day. I killed a set in a few weeks going from 90+ to 20 4x a day in my youth when they put roadworks ramps on a fast road. When it started to cost me money I soon slowed down

Still looks more like firescale to me, would fit with all the paint burning off

Well as its mainly driven by my daughter no I can't be certain, but while she doesn't hang about, I've never seen her abusing the car or brakes. As its a 1.2 and only 69 HP I cant imagine the brakes wouldnt take most of whats thrown at them on such a light weight car. Also she works nights so there is little traffic about when the car is used so not much need for hard braking. Nursing my cars extends to not putting the cars away with wet brakes after washing, and ensuring that when garaged handbrakes are not left on, and running in discs and pads is a no brainer too. This time I am going to check the brakes in depth 3 times a year and ensure they are re-greased. I am impressed by the honing on the new discs, not something I have ever seen on cheaper brands. Tnere are of course so many products sold in the brakes line, that not having fitted them they could have been anything. I will say that the coated VW discs I have used are the only ones I have seen for years that behave as expected for a reasonable time and I suppose the coated Ferodo discs I put on the Bravo didnt give issues either. I have no issue with disc and pad replacement each time, as the non asbestos pads are so much harder these days, but do expect to get to the end of the pads life. These ones were only half worn.

 

[The Panda Nut]

is it cracked ?
photo 3
12 o'clock

could just be the way its photo'd

No the pad seems to be responsible for trying to cut the disc in two! I have never seen anything like this before.

 

[The Panda Nut]

I'd be keen to investigate further

needs a mic or callipers to measure the thickness

I don't think there's enough metal mass left to take the heat away they start at 10.9 mm with a minimum of 9.2mm Which is under a mm wear per side. To thin and they will overheat much too easier

A lot can be told by looking at pads. They should all have roughly the same amount of even wear, (no wedging) left and right sides should be identical.

I fell like want the parts in my hands.

Last time cleaned and sorted the discs were almost dead on 11mm jusf few thou over. Virtually no wear at all.... except see below. New discs are 12.4 thick I believe.

 

[koalar]

No the pad seems to be responsible for trying to cut the disc in two! I have never seen anything like this before.

are you sure the bed in was followed ?

pads have a rough surface on them to clean up discs

"New brake pads do not provide full performance during the first 100 to 200 miles (200 to 300 km) and must first be broken in ⇒

 . To some extent, you can make up for the somewhat reduced performance by applying more pressure to the brake pedal. But, during the break-in period, the stopping distance for hard braking and emergency braking will be longer until the brakes are fully broken in. Avoid hard braking and situations that might require hard braking (such as following other vehicles too closely) – especially during the break-in period."

 

[koalar]

doesn't matter it a 1.2 it still does 70 on the slip road, If you leave the braking to the last minute the will be glowing yellow

I just changed pads in mine after two years. The other half is very last minute on the brakes, annoying as if I was driving it the pads would out live the car.

we really need two cars, fit the same pads and discs, and check after 10K miles, I bet its more how its driven.

 

[DaveMcT]

New discs are lightly zinc plated for rust protection. It quickly wears off (more likely burns off) but will affect brake performance until it does.

Brakes with the back side (inside?) of the disc corroded and mangled have suffered from too little brake pressure on that side. The only cause is they have not been maintained correctly. It might need a new caliper. More likely a full overhaul with new pins and bushes will do the job.