X7 Unexpected Rear Brakes Change + Coated Brake Discs

[EDC5]

So after driving for a few days with what I thought was a stone lodged in the brakes, I decided to investigate the source of a squealing / grinding noise. From the outside there appeared to be plenty of material left on the rear pads.....

However a proper look gave a much different view:



What you can see is the backing plate, the inside brake pad had worn completely! Fist off I was shocked that this wasn't flagged as an advisory last December. And secondly I was slightly concerned that the inner pad had worn so much more than the outer one.

In addition, the worn brake pad had made a mess of the disc surface:



And a closer look here:



So, straight off to buy spares. I opted for Pagid parts for reasons that I'll mention later.

Getting the old discs off was a bit of a pain, had to use the blowtorch to loosen it. I didn't use too much heat as I didn't want to boil the bearing or anything. Luckily the caliper and carrier came out without much fuss.

Very lucky that nothing was seized as I think the discs on the back have never been changed before and the car is 10 years old now.

A look at the completely worn pad... to my shame



The old discs were past their best too, heavily corroded on the edge and centre:



Whilst I had access to the hub I decided to remove my rusted disc guard. I got as much of the surface rust off as possible then used some high temp paint to tidy them up a bit:



Much better



I also cleaned up the ABS ring(s) which had attracted a lot of ferrous crud:



Now on to the shiny new parts.

As I say I opted for Pagid parts, not least because of their special coating of powdered Aluminium and Zinc which I found out is called Geomet 360, info here: https://www.anochrome.com/geomet-coating/ .



The advantages of this coating are that the centre and edge of the disc shouln't ever corrode and there is no need to clean the protective oil layer off like normal brake discs.

I may be late to the game here but the number of corroded brake discs I see is huge and it can spoil the appearance of a car in my view.

I think you'll agree that they do look the part too, especially compared to the corroded old ones.





So now I'm just waiting for someone to tell me that this fancy coating wears off after a few weeks....

Just want to mention the need for a piston wind back tool on the rear calipers. Whilst this tool would have been useful, I made do with a pair of very sturdy pliers that fit snugly into the holes in the piston. I had to use an 'extreme' amount of vertical force whilst turning to get the piston to retract. So whilst it is possible to do it without the wind-back tool ,I'm sure it is a lot easier with.

[Hell Razor5543]

Two tricks to help make it easier to remove brake disks. I do the first one when I work on the brakes, but I have not had to try the second trick.

1, Coat the surface of the hub and inner brake disk with copper slip grease. That should help stop them from binding/rusting together.

2, (Drive wheels only). Should you find the disks have become firmly attached to the hub, lift the drive end of the car into the air, remove the wheels and disk retaining bolts, start the engine, put her into gear, let the hubs spin and then (without using the clutch) tread on the brakes. This should (through the twisting action) break the disks free of the hub (it has been said this will make a loud noise doing this). Stop the engine, and check the disks. Should only one disk be free secure it to the hub (with the securing bolts and the wheel bolts) and try again (you may need, depending on the differential, put it into the opposite gear from last time).

[moizeau]

Isn't there a low warning cable that earths to the disk? It just looked like that was the remains on the 4th picture. It is easier with the special tool. On the BX I have a screwdriver that has a square shank, for the Saab I have a flat steel bar with two bits off nail welded on.

[moizeau]

Always do the copper slip James nut the 2nd tip.....very nice. Much better than turning the wheel and wielding a soft hammer that becomes less soft as frustration sets in.

[EDC5]

Very interesting, thanks for the suggestions. I'll bear them in mind for next time.

There are no low pad warning for the brakes on the rear, which is a bit of a shame as it may have come in useful (and saved my discs). But since the brake discs were worn out too no harm done.

I'm sure I read somewhere that copper grease it to be avoided these days on brake parts... not sure if there's any truth in that to be honest.

[moizeau]

Not on pads Elis as you know, but certainly on wheel nuts, disc screws, in between the hub and disc etc. Why 'these days' the mechanics are the same. I'd be interested in reading the document that says 'don't'.

[Hell Razor5543]

Very interesting, thanks for the suggestions. I'll bear them in mind for next time.

There are no low pad warning for the brakes on the rear, which is a bit of a shame as it may have come in useful (and saved my discs). But since the brake discs were worn out too no harm done.

I'm sure I read somewhere that copper grease it to be avoided these days on brake parts... not sure if there's any truth in that to be honest.

Obviously you do not want grease on any of the friction points, but grease on contact locations (such as between the hub and the disk) should not be an issue (unless you are careless), as it will not affect the efficiency of the braking.

[Sloppysod]

I'm sure I read somewhere that copper grease it to be avoided these days on brake parts... not sure if there's any truth in that to be honest.

I have used "Copper Slip" Grease on all my vehicles (bikes included) but after reading this may be slightly more careful where I use it
https://textar-professional.com/textar- ... rn-brakes/

I fitted Brembo discs to mine earlier this year with the same coating for the same reason and they still look good, I am with you, rusty discs make a car look shabby.

Remember to run your new disks in for about 100 miles or so.

[moizeau]

Just read that Stu, I think it's an ad, maybe wrong. Yes there are chemical reactions between different metals, and if you put salt water in there as well, lots. Look at the back of Series Landys between the rear chassis and body. Ali and steel and water. It will be removed reasonably frequently as opposed to the 100 years plus for the Statue of Liberty I'll stick with copper slip.
Cheers all the same

[GiveMeABreak]

Those discs do look the part. I must I have had all mine replaced at the dealers previously, but the discs rust very quickly I’ve found, somwill certainly be looking at getting these Pagid ones if they remain in that state!

Will look forward to some pictures down the line Elis to see if they bear out the marketing. Sound job.

[GiveMeABreak]

One thing I also have to say is the alloys on my X7 are truly badly finished. I’ve never such badly finished alloys on a vehicle. They are full of lumps and bubbles near the inner parts. I was washing the car a couple of days ago and really noticed how bad they were. I think I’ll be leaving the various tar splodges on there for added protection!

[xantia_v6]

The thing with copper grease on brake parts is that brakes can get very hot when used to full potential, and copper grease melts when hot and becomes quite slippery, so you should only use as much as you would be happy for it to be coating the friction surfaces in an emergency situation.

[white exec]

Take the point about risk of galvanic reaction between copper and aluminium, so a reason not to use it on alu wheels. Steel discs mated to a steel hub (and steel brake pad backs in a steel caliper) is a different matter though, and probably why years of this hasn't SFAIK caused a problem.

I do recall being told, though, that wheel nuts/studs should not be greased (but simply wiped with grimy fingers!). Friction on these nuts and studs actually performs the useful function of 'locking' them tight - witness the brief scrawp when undoing them.

[myglaren]

I think Molyslip grease has a high melting point and is unlikely to react with metal components.
I have tons of Copaslip and Molyslip, some of it 40 years old (I don't use much of it)

Chucked a load of Lithium grease out as it had been there so long and the tin was tatty. Regretted it soon after naturally.

[EDC5]

Not on pads Elis as you know, but certainly on wheel nuts, disc screws, in between the hub and disc etc. Why 'these days' the mechanics are the same. I'd be interested in reading the document that says 'don't'.

Yeah, I don't see what would be wrong with using it on the sliding portion of the brake pads etc. I used high temp silicone grease instead, hope it lasts.

Remember to run your new disks in for about 100 miles or so.

What exactly is the running in procedure? light braking I'm assuming?

Those discs do look the part. I must I have had all mine replaced at the dealers previously, but the discs rust very quickly I’ve found, somwill certainly be looking at getting these Pagid ones if they remain in that state!

Will look forward to some pictures down the line Elis to see if they bear out the marketing. Sound job.

One thing I also have to say is the alloys on my X7 are truly badly finished. I’ve never such badly finished alloys on a vehicle. They are full of lumps and bubbles near the inner parts. I was washing the car a couple of days ago and really noticed how bad they were. I think I’ll be leaving the various tar splodges on there for added protection!

I think they look great and I'll certainly update the thread should they fail to meet expectations. You're right, the alloys are bubbling and the paint is falling off on the inside surface if the alloy. I assume they'll need refurbing at some point!

As far as i'm aware, the only external surface that needs good lubrication on the brakes are the tracks the pads slide in on the carrier. Without grease the pads can seize in the carriers (as it appears to have done on mine).

If the silicone grease leaks off from high temp , I'll replace it with some heavier duty grease as it's essential that the brake pads can slide in the carriers.