Technical Brakes again...

[koalar]

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.

are you looking at the pictures correctly

they have equal wear front and back the lip has broken off one side, look at the centre

i can pretty much gaurentee the groove around the centre is due the brakes being used very hard. Been there done that, had disc look like that, cost too much now drive like a granny. They now stay nice and flat. Just have to rough them occasionally as they tend to glaze,

you dont have to drive fast to destroy discs and pads, a lot of heat is generated if you only use the brakes to slow for junctions, leaving your foot on the brake while waiting for the road to clear doesn't help.

 

[koalar]

Resurrecting this old thread

Not too bad this side but still feels like a millimetre or two of wear

But there isn’t it just chips off and there is virtually no lip or wear

 

[Pugglt Auld Jock]

Resurrecting this old thread

Not too bad this side but still feels like a millimetre or two of wear

But there isn’t it just chips off and there is virtually no lip or wear


View attachment 410350

As long as the other side of the disc is in a similar condition then that looks as if it should have many hours of happy motoring in it yet. Little in the way of a lip and a pretty smooth and score free surface. I'd be happy enough to put a new set of pads onto this but remembering that, even with the little wear that can be seen, it's going to be necessary to drive conservatively for a couple of hundred miles or so to let the new pads bed in properly. I know you are an "aware" person koalar, so don't need to be reminded of that! Ascertaining disc wear and deciding if new discs are needed is often difficult for someone not used to looking at this sort of thing on a regular basis compounded by the common finding that the inner disc surface is often in poorer condition than the more easily checked outer surface - for whatever reason.

My youngest boy's next door neighbour is caught up in a dispute around this at this time. They bought their 18 plate Hyundai SUV "tank like thing" a few months ago from a large dealer. I'm not sure why but the car was in at the wee local garage they have used for years and he has told them they need new discs due to severe wear and pitting, especially on the "inside". Although not a garage I've had dealings with it's a long established concern with a good reputation - a "name" I've been aware of for many years - and I'd be inclined to believe his opinion. Last night I had a very quick and cursory look at the discs through the alloys as we were dropping the grandchildren back after a day of hectic activity with them, so was only able to briefly inspect the outer face of the discs. Pretty predictable in that the fronts look not particularly scored but definitely have a noticeable lip and the rears have about a third of their surface corroded. All four have obviously had new pads fitted fairly recently. My guess would be that the pads were fitted when the car was prepared for sale. Based on what I saw last night and the fact that I know it's often the case that dealer maintained cars - as against "coddled" enthusiasts cars like ours - often have issues with brakes due to minimal attention, I'd have been renewing the discs when the pads were done. Of course the selling garage will have been trying to keep as much profit as possible which, no doubt, is why it would seem it got pads only. Who can say what condition the discs were in at the time of sale? The problem arises because the wife thinks that the seller said new discs would be fitted so is arguing that the cost of the brake rebuild now being recommended should be covered by the selling garage. Good luck with that one say I! I'm hoping my son will keep me updated on the outcome.

 

[DaveMcT]

My left-hand front disc looked evenly worn on the outside and both pads have about 50% material. It looked fine for the MOT.

Erm - no. The "inside" of the disc has a wear groove down the middle. At least 10mm of pad area towards the rim is badly pitted with rust. The disc and pads are toast. The car drives just fine but I need to sort out what has happened. Simply fitting new parts wont be enough.

The other side looks ok but the axle set will have to be replaced. £30 for QH brand parts isn't too bad.

 

[koalar]

As long as the other side of the disc is in a similar condition then that looks as if it should have many hours of happy motoring in it yet. Little in the way of a lip and a pretty smooth and score free surface. I'd be happy enough to put a new set of pads onto this but remembering that, even with the little wear that can be seen, it's going to be necessary to drive conservatively for a couple of hundred miles or so to let the new pads bed in properly.

Yep discs are fine, just angled the hammer and knocked off the inside as well. Then chiselled off the inner as well

I was surprised just how much the metal had grown

The other side was slightly worse at around 2 mm. But couldn’t get a photo as my oily fingers failed on the touch screen

Which looks like it’s worn down by 4 mm when in reality it’s less than 1 mm

 

[The Panda Nut]

Yep discs are fine, just angled the hammer and knocked off the inside as well. Then chiselled off the inner as well

I was surprised just how much the metal had grown

The other side was slightly worse at around 2 mm. But couldn’t get a photo as my oily fingers failed on the touch screen

Which looks like it’s worn down by 4 mm when in reality it’s less than 1 mm

Much like our 312. I cleaned the disc rear faces with my sander wheel on my grinder. Then flatted the pads with a file. All seem swell after some months and the MOT was fine. The 169 had rusted so badly, and with the disc scored by something in the pad so badly it loked ready to fail new discs and pads were fitted. Blueprint.com coated discs are a superb fit and decent price. The brakes now run in are a vast improvement. Im disappointed the MOT didnt pick up the problem. Caliper checks now done twice a year! 35 years ago you never got discs rusting so badly and would run several sets of pads per set of discs. I think its all down to asbestos free brake pads . For some reason they just dont clear the rust in use and if you dont maintain to the nines cause issues.

 

[DaveMcT]

I've fitted new pads and new discs. I can't find anything wiring with the calipers so no idea what the inside face had worn so strangely. It's like the centre band on the pads was biting harder than the edge 10mm of pad area.
The discs and pads were not badly worn but that pitting won’t pass mot. Not with my tester anyway.

 

[The Panda Nut]

I've fitted new pads and new discs. I can't find anything wiring with the calipers so no idea what the inside face had worn so strangely. It's like the centre band on the pads was biting harder than the outer and inner 10mm of pad area. But ONLY on the hydraulic side of both brakes. It's very odd because the pads all look the same - left, right, inside and outside.

Ha the problem. I cant fathom why this has become a problem. You shouldnt need to dismatle the calipers every three months to stop this hapening. Its bad design, and bad design of a braking system!!!!! Bendix seemd to be the perpetrator as their brakes starerted this trend in caliper design that seems to be at the bottom of it. In the old days you used to have to remove two pins top and bottom from the Girling calipers, and Lucas brakes were similar. There was no rubber in teh mountings or sliding mechansim. The along came this new design direction and the introduction of slider pins and bushes and since then I have grown sick of changing discs before its necessary. It may be that the new design reduces squeal?

Panda, CLio, Renault 5, Renault Laguna all afflicted this way. Are there any engineers with theories of why this occurs. It seems that the rust on the disc edge creeps under the outer lip of the pads. And then being harder than teh steel of the disc forces teh edge of the pad up. I think then the othe inner edge of the pad wears a bit more. The centre stays wearing due to overwhelming pedal force but the rus develops under the inner edge of the pads resulting in the braked area of the disc thats not rusting getting smaller and smaller. Wh all systems the same. Whatever the caaue its not something that afflicts our Seat does nearly to the same extent. Coated discs do seem to push doomsday away a fair bit sooner.

Whatever the cause I would stick all teh rusty disc somewhere the originator of this probel wouldnt want! Im going to try cleaniong the discs and applying cold galve paint to the disc non wearing parts. Caliper bushes for 1 side from Fiat for the Panda 4x4. £56. -And that is KINROBBERY Fiat!!!!!!

 

[koalar]

I've fitted new pads and new discs. I can't find anything wiring with the calipers so no idea what the inside face had worn so strangely. It's like the centre band on the pads was biting harder than the edge 10mm of pad area.
The discs and pads were not badly worn but that pitting won’t pass mot. Not with my tester anyway.

As long as they were decent pads it looks like the pads are binding in the bracket and the pads bending in the middle. Not uncommon.

They have to be a really sloppy fit.

 

[koalar]

Ha the problem. I cant fathom why this has become a problem. You shouldnt need to dismatle the calipers every three months to stop this hapening. Its bad design, and bad design of a braking system!!!!! Bendix seemd to be the perpetrator as their brakes starerted this trend in caliper design that seems to be at the bottom of it. In the old days you used to have to remove two pins top and bottom from the Girling calipers, and Lucas brakes were similar. There was no rubber in teh mountings or sliding mechansim. The along came this new design direction and the introduction of slider pins and bushes and since then I have grown sick of changing discs before its necessary. It may be that the new design reduces squeal?

Panda, CLio, Renault 5, Renault Laguna all afflicted this way. Are there any engineers with theories of why this occurs. It seems that the rust on the disc edge creeps under the outer lip of the pads. And then being harder than teh steel of the disc forces teh edge of the pad up. I think then the othe inner edge of the pad wears a bit more. The centre stays wearing due to overwhelming pedal force but the rus develops under the inner edge of the pads resulting in the braked area of the disc thats not rusting getting smaller and smaller. Wh all systems the same. Whatever the caaue its not something that afflicts our Seat does nearly to the same extent. Coated discs do seem to push doomsday away a fair bit sooner.

Whatever the cause I would stick all teh rusty disc somewhere the originator of this probel wouldnt want! Im going to try cleaniong the discs and applying cold galve paint to the disc non wearing parts. Caliper bushes for 1 side from Fiat for the Panda 4x4. £56. -And that is KINROBBERY Fiat!!!!!!

It is strange as both I and the other half don’t have this problem. I fit whatever parts available at the time. Blueprint last time

I drive quite carefully and anticipate and slow down before junctions
But the other half doesn’t and drives straight to the junction

We do both stay below 60mph most of the time

Weight/number of people in the car
Hills
City driving
We do both stay below 60mph most of the time


Cheshire is very flat

 

[DaveMcT]

As long as they were decent pads it looks like the pads are binding in the bracket and the pads bending in the middle. Not uncommon.

They have to be a really sloppy fit.

I dont remember where the pads were from but probably a local supplier.

The new pads are QH which I bought with QH discs. They fit nicely but to be fair the old ones were not tight in the carrier. I ended up with Borg n Beck discs bought locally, because I ordered the wrong parts (rushed job & clicked the wrong advert).

MoT says there is a slight variation on LHS brake. So I will have to get a DTI on the case. It might need a new hub.

 

[The Panda Nut]

I dont remember where the pads were from but probably a local supplier.

The new pads are QH which I bought with QH discs. They fit nicely but to be fair the old ones were not tight in the carrier. I ended up with Borg n Beck discs bought locally, because I ordered the wrong parts (rushed job & clicked the wrong advert).

MoT says there is a slight variation on LHS brake. So I will have to get a DTI on the case. It might need a new hub.

I like my brkaes to have the same reading each side too, But the allowed variation is I think 25%. 25%!!!!! Thats just daft. The state of the discs shouldnt fail an MOT if they still fall in tolerance apparently. In my view it certainly should do. My view is you want 100% of the pad working not 30% so I make sure they are all shiny and its a full time job these days. Even with new discs and pads and new fluid we still had a difference with our 169. Ultimately with ABS and EBD it doesnt matter if they work as the system works max and the abs governs lockup so the car will stop straight. With 8% variance I cannot feel anything on the road. I suspect some of the difference may be the test gear varying a little too. As tyou say bearings, different length drive shafts, diff and gearbox bearings all have an effect. A few years ago we didnt have such accurate test gear so we didnt worry as much. I am happy the car is as good as it can be. Relax, have a Perroni and chill. Just make sure it and akt u LOOK good!

 

[vexorg]

I tend to change discs along with the pads these days, they are generally not that expensive and dont worry about all the bedding in so much into the old grooves.

 

[DaveMcT]

I need to clarify some points.

Both front brakes had this strange rusting problem. 10mm wide bands of nasty rust pitting under the inner and outer edges of pads contact area on inside face. Outside face is normal. The discs were otherwise within normal wear limits. Pads 50% worn and not signs of heat abuse. The affected pads look almost normal you have to look very close to see the wear "steps".

Left had side was worse but there was no difference in braking effect. No pull on brakes. Last year's MOT had a comment about disc corrosion but not enough to fail MoT. Last years MOT also commented about disc runout (brake force variation) though I could never feel anything on the pedal.

The brakes now have new Borg & Beck discs (very not cheap) with QH pads. The brake pistons move nicely (pushed back with bleed nipples open to clear old fluid. Brake pad carriers hold the pads correctly no sticking. Retaining pins are clean.

The LHS continues to have a brake force variation (disc not running true). This is a different issue. I will need to get a DTI and measure, but probably need to fit a new hub and wheel bearing. The disc mounting faces are spotlessly clean.

 

[DaveMcT]

I tend to change discs along with the pads these days, they are generally not that expensive and don't worry about all the bedding in so much into the old grooves.

Me too but not when pads are 50% worn. I only spotted this problem because I had the drive shafts out for changing the clutch. I don't normally closely inspect the brake disc inner face. Pad thickness is usually enough. Clearly, it's not enough.

 

[vexorg]

I suppose it will just depend on how much use they have, both in terms of sitting around, and braking force when driving.

 

[The Panda Nut]

are you looking at the pictures correctly

they have equal wear front and back the lip has broken off one side, look at the centre

i can pretty much gaurentee the groove around the centre is due the brakes being used very hard. Been there done that, had disc look like that, cost too much now drive like a granny. They now stay nice and flat. Just have to rough them occasionally as they tend to glaze,

you dont have to drive fast to destroy discs and pads, a lot of heat is generated if you only use the brakes to slow for junctions, leaving your foot on the brake while waiting for the road to clear doesn't help.

Close examination of the pads revealed the grove was caused by the Pad having a large thing in it. These scintered metal pads are funny things and this looked like an oversize lump from the manufacturing process. I have never seen the like. As the discs are screwed anyway it didn't matter. Its not hard use, Im the hardest driver of the three of us and I only drive this car very occasionally. I didnt choose or fit these pads and use Fiat or Ferodo as OE suppliers only on most occasions. I think this time I have used Blueprint.com stuff. (These are Febi Bilstein by another name) The discs are certainly excellent quality and beautifully honed. I guess this is 20 - 40K of miles driven on the old discs. I note your suggestion of pads flexing and bending. I am not sure I agree but I have wondered if this was going on. I'm going to consider the thickness of the pad back plates and measure some to see if there is any difference. Its been three months I think since the new brakes were fitted so I think I will have a look and see how tings look and post a pic in due course. I usually run a file on the pad edges where they contact the calipers and remove the paint. In future I shall ensure they are a fraction looser. The problem must relate to pads / calipers sticking if one side of the disc is rust free. If the caliper floats as it should this just should not happen. I think your statement about plenty of play being best may be key.

 

[koalar]

Yep they should be really loose, and rattle around. Some of the third party pads need a little file on the lugs to remove the paint

 

[DaveMcT]

My inner pads were correctly loose and the contact surfaces look normal. You have to look VERY closely to see the slightly greater wear on the inner and outer 25% of the pads. It was a disc corrosion problem but why it hasn't gone across the whole width is anyone's guess. Both sides were affected though LHS was worse than RHS. There was no steering pull on braking.

 

[koalar]

At least 3 years and 50,000 miles possibly many more on the discs

No yearly service just change the pads when worn out

I have had 3x pandas and 1x punto

Even fitting the cheapest parts none

End up like this

Or

Something is wrong
Dragging and overheating

Standing on the brakes from high speed

Jamming and not giving even pressure

Poor quality parts

I am not there.

But I can say when they are working correctly and used correctly they are just fit and forget and run on and on for years

It’s not new asbestos free pads or different grade steel discs