Omega Owners Forum

Chat Area => General Car Chat => Topic started by: tunnie on 18 June 2013, 18:53:03

Title: Why do inner discs corrode?
Post by: tunnie on 18 June 2013, 18:53:03
It appears to be "normal" for the inside lower part of disc to rust up, just wondering what can cause this? Its not specific to this car, as many people have had exactly same  :-\

Outside is always perfect:

(https://dl.dropboxusercontent.com/u/803897/Omega/Brakes/2013-06-18%2016.31.18.jpg)

Yet the inside goes like this:

(https://dl.dropboxusercontent.com/u/803897/Omega/Brakes/2013-06-18%2016.31.12.jpg)

The Pad warning had come on, the discs themselves on the outside at least had plenty of life left, but because the inside was feked, I could not just slap new pads in, so discs and pads had to be fitted:

(https://dl.dropboxusercontent.com/u/803897/Omega/Brakes/2013-06-18%2016.30.39.jpg)

The caliper is free and moving fine, the pads were fitted correctly.  Anything we can do to prevent this?  :-\
Title: Re: Why do inner discs corrode?
Post by: henryd on 18 June 2013, 18:59:31
The inside of the disc lives in a much harsher enviroment than the outside,any crap thrown up by the opposite wheel is going to splash the inside of the disc causing it to corrode quicker,made worse by many modern cars not have splash shields behind the discs any more.
Title: Re: Why do inner discs corrode?
Post by: VXL V6 on 18 June 2013, 19:00:02
Presumably its something to do with the caliper design, the inside pad is pressed against the disc with the piston, the outside is pressed against the disc by the force of the caliper movement.
Title: Re: Why do inner discs corrode?
Post by: TheBoy on 18 June 2013, 19:04:30
I think its caliper design, but only seen this on (virtually all) Omegas, never other cars...
Title: Re: Why do inner discs corrode?
Post by: Mr.OmegaMan on 18 June 2013, 19:05:30
Same problem on both mine also  :-\, Still have the old discs outside will take a quick pic.
Title: Re: Why do inner discs corrode?
Post by: tunnie on 18 June 2013, 19:10:32
The inside of the disc lives in a much harsher enviroment than the outside,any crap thrown up by the opposite wheel is going to splash the inside of the disc causing it to corrode quicker,made worse by many modern cars not have splash shields behind the discs any more.

Its more than that though, the pad wears un-evenly, as others have mentioned it appears to be a caliper design issue. Just wondering if anything can be done to prevent it  :-\
Title: Re: Why do inner discs corrode?
Post by: TheBoy on 18 June 2013, 19:14:14
The inside of the disc lives in a much harsher enviroment than the outside,any crap thrown up by the opposite wheel is going to splash the inside of the disc causing it to corrode quicker,made worse by many modern cars not have splash shields behind the discs any more.

Its more than that though, the pad wears un-evenly, as others have mentioned it appears to be a caliper design issue. Just wondering if anything can be done to prevent it  :-\
Not that you'd be prepared to do...
Title: Re: Why do inner discs corrode?
Post by: tunnie on 18 June 2013, 19:16:07
The inside of the disc lives in a much harsher enviroment than the outside,any crap thrown up by the opposite wheel is going to splash the inside of the disc causing it to corrode quicker,made worse by many modern cars not have splash shields behind the discs any more.

Its more than that though, the pad wears un-evenly, as others have mentioned it appears to be a caliper design issue. Just wondering if anything can be done to prevent it  :-\
Not that you'd be prepared to do...

Shame  :(
Title: Re: Why do inner discs corrode?
Post by: Webby the Bear on 18 June 2013, 19:16:38
its interestin how the rim of corrosion is completely even.
Title: Re: Why do inner discs corrode?
Post by: TheBoy on 18 June 2013, 19:17:21
The inside of the disc lives in a much harsher enviroment than the outside,any crap thrown up by the opposite wheel is going to splash the inside of the disc causing it to corrode quicker,made worse by many modern cars not have splash shields behind the discs any more.

Its more than that though, the pad wears un-evenly, as others have mentioned it appears to be a caliper design issue. Just wondering if anything can be done to prevent it  :-\
Not that you'd be prepared to do...

Shame  :(
£100 every couple of years (or every 5 in your case ;D), not worth the bother...
Title: Re: Why do inner discs corrode?
Post by: Mr.OmegaMan on 18 June 2013, 19:19:31
Been standing outside for a few weeks so a little rusty.

(http://i1158.photobucket.com/albums/p620/Agemo_Legend/F296CCFA-F024-434E-94AF-59B176F01EB7-2106-000000BE0F1F4294_zps70bb05f3.jpg) (http://s1158.photobucket.com/user/Agemo_Legend/media/F296CCFA-F024-434E-94AF-59B176F01EB7-2106-000000BE0F1F4294_zps70bb05f3.jpg.html)
(http://i1158.photobucket.com/albums/p620/Agemo_Legend/8025073B-72CA-4E13-BB1C-1DEF3568F2D4-2106-000000BE1401218E_zps744f23ad.jpg) (http://s1158.photobucket.com/user/Agemo_Legend/media/8025073B-72CA-4E13-BB1C-1DEF3568F2D4-2106-000000BE1401218E_zps744f23ad.jpg.html)
(http://i1158.photobucket.com/albums/p620/Agemo_Legend/60818600-AFB2-4158-A11C-69D3C6C7B3D2-2106-000000BE0A01712C_zpsa88858ae.jpg) (http://s1158.photobucket.com/user/Agemo_Legend/media/60818600-AFB2-4158-A11C-69D3C6C7B3D2-2106-000000BE0A01712C_zpsa88858ae.jpg.html)
Title: Re: Why do inner discs corrode?
Post by: tunnie on 18 June 2013, 19:19:57
The inside of the disc lives in a much harsher enviroment than the outside,any crap thrown up by the opposite wheel is going to splash the inside of the disc causing it to corrode quicker,made worse by many modern cars not have splash shields behind the discs any more.

Its more than that though, the pad wears un-evenly, as others have mentioned it appears to be a caliper design issue. Just wondering if anything can be done to prevent it  :-\
Not that you'd be prepared to do...

Shame  :(
£100 every couple of years (or every 5 in your case ;D), not worth the bother...

I'd be upset at anything less than that. New discs went on 2.2 this year, last set, was used for that guide  ::)

So that is 6 years from a set of discs, about 70k i think  :-\
Title: Re: Why do inner discs corrode?
Post by: Andy H on 18 June 2013, 19:29:36
Presumably its something to do with the caliper design, the inside pad is pressed against the disc with the piston, the outside is pressed against the disc by the force of the caliper movement.
I would expect the piston to press the inner pad against the disk first and then, after overcoming any stiction on the slider pins, the frame would move and press outer pad against the disk.

On the Omega I don't think the design of the caliper is the issue. I think it is due to additional corrosion of the inner face (as described above) and intermittent use of the car. I haven't had the issue with my Omegas but I have used them as daily drivers. I expect that the cars that have shown the problem have been used for weekends and holidays.
Title: Re: Why do inner discs corrode?
Post by: tunnie on 18 June 2013, 19:33:40
Presumably its something to do with the caliper design, the inside pad is pressed against the disc with the piston, the outside is pressed against the disc by the force of the caliper movement.
I would expect the piston to press the inner pad against the disk first and then, after overcoming any stiction on the slider pins, the frame would move and press outer pad against the disk.

On the Omega I don't think the design of the caliper is the issue. I think it is due to additional corrosion of the inner face (as described above) and intermittent use of the car. I haven't had the issue with my Omegas but I have used them as daily drivers. I expect that the cars that have shown the problem have been used for weekends and holidays.

One shown is used every week, on a 150 mile round trip. The 2.2 was the same, that was in very regular use too.
Title: Re: Why do inner discs corrode?
Post by: TheBoy on 18 June 2013, 19:34:44
Presumably its something to do with the caliper design, the inside pad is pressed against the disc with the piston, the outside is pressed against the disc by the force of the caliper movement.
I would expect the piston to press the inner pad against the disk first and then, after overcoming any stiction on the slider pins, the frame would move and press outer pad against the disk.

On the Omega I don't think the design of the caliper is the issue. I think it is due to additional corrosion of the inner face (as described above) and intermittent use of the car. I haven't had the issue with my Omegas but I have used them as daily drivers. I expect that the cars that have shown the problem have been used for weekends and holidays.
I use mine pretty much daily, and the brakes are definately used enough to stop rust build up, so I remain unconvinced.
Title: Re: Why do inner discs corrode?
Post by: henryd on 18 June 2013, 19:35:04
It's not just omega's, I see many different makes with the same issues  :-\
Title: Re: Why do inner discs corrode?
Post by: VXL V6 on 18 June 2013, 19:35:34
Presumably its something to do with the caliper design, the inside pad is pressed against the disc with the piston, the outside is pressed against the disc by the force of the caliper movement.
I would expect the piston to press the inner pad against the disk first and then, after overcoming any stiction on the slider pins, the frame would move and press outer pad against the disk.

Yep, agree with that.

I did wonder if the inner pad could vibrate slightly more movement on the piston than the outer pad that has two pressure points of the caliper body against it.
Title: Re: Why do inner discs corrode?
Post by: pirate on 18 June 2013, 19:37:57
modern disc,s are realy crap metal and rust between box and fitting to the car i always paint middle of disc,s with american rotor paint stops them furring up,also looks alot better,
one of the worse makes out there are bmw disc,s and calipers go rusty in 4 mths,wifes suzuki swift now 5 years old nothing.
Title: Re: Why do inner discs corrode?
Post by: Andy H on 18 June 2013, 19:46:39
Presumably its something to do with the caliper design, the inside pad is pressed against the disc with the piston, the outside is pressed against the disc by the force of the caliper movement.
I would expect the piston to press the inner pad against the disk first and then, after overcoming any stiction on the slider pins, the frame would move and press outer pad against the disk.

On the Omega I don't think the design of the caliper is the issue. I think it is due to additional corrosion of the inner face (as described above) and intermittent use of the car. I haven't had the issue with my Omegas but I have used them as daily drivers. I expect that the cars that have shown the problem have been used for weekends and holidays.

One shown is used every week, on a 150 mile round trip. The 2.2 was the same, that was in very regular use too.
I wouldn't call that daily driving  :-\

I can well believe that TB uses the brakes enough to sweep the surface rust off  ;D but I think the damage is done when a car stands for 4 or 5 days at a time.
Title: Re: Why do inner discs corrode?
Post by: tunnie on 18 June 2013, 19:50:31
Presumably its something to do with the caliper design, the inside pad is pressed against the disc with the piston, the outside is pressed against the disc by the force of the caliper movement.
I would expect the piston to press the inner pad against the disk first and then, after overcoming any stiction on the slider pins, the frame would move and press outer pad against the disk.

On the Omega I don't think the design of the caliper is the issue. I think it is due to additional corrosion of the inner face (as described above) and intermittent use of the car. I haven't had the issue with my Omegas but I have used them as daily drivers. I expect that the cars that have shown the problem have been used for weekends and holidays.

One shown is used every week, on a 150 mile round trip. The 2.2 was the same, that was in very regular use too.
I wouldn't call that daily driving  :-\

I can well believe that TB uses the brakes enough to sweep the surface rust off  ;D but I think the damage is done when a car stands for 4 or 5 days at a time.

Never that length of time, over weekend it could stand at most. Still don't think that can be enough to cause that level or poor wear  :(

Like I say, 2.2 also is the same, that was a daily driver.
Title: Re: Why do inner discs corrode?
Post by: Andy H on 18 June 2013, 19:56:20
Maybe it is the new style roadsalt, it (allegedly) has something in (animal fat? mollasses?) that makes it stick to the road for longer. Unfortunately it also sticks to windscreens, motorcycle helmet visors and (probably) brake disks.
Title: Re: Why do inner discs corrode?
Post by: TheBoy on 18 June 2013, 19:56:41
Presumably its something to do with the caliper design, the inside pad is pressed against the disc with the piston, the outside is pressed against the disc by the force of the caliper movement.
I would expect the piston to press the inner pad against the disk first and then, after overcoming any stiction on the slider pins, the frame would move and press outer pad against the disk.

On the Omega I don't think the design of the caliper is the issue. I think it is due to additional corrosion of the inner face (as described above) and intermittent use of the car. I haven't had the issue with my Omegas but I have used them as daily drivers. I expect that the cars that have shown the problem have been used for weekends and holidays.

One shown is used every week, on a 150 mile round trip. The 2.2 was the same, that was in very regular use too.
I wouldn't call that daily driving  :-\

I can well believe that TB uses the brakes enough to sweep the surface rust off  ;D but I think the damage is done when a car stands for 4 or 5 days at a time.
Rarely a day in the year when the Silver Bullet isn't used. Maybe occasionally a Sunday it doesn't go out. It suffers as much as all the others.
Title: Re: Why do inner discs corrode?
Post by: TheBoy on 18 June 2013, 19:57:29
Maybe it is the new style roadsalt, it (allegedly) has something in (animal fat? mollasses?) that makes it stick to the road for longer. Unfortunately it also sticks to windscreens, motorcycle helmet visors and (probably) brake disks.
I think that has a lot to do with the general car corrosion, but I don't think explains this scenario  :-\
Title: Re: Why do inner discs corrode?
Post by: chrisgixer on 18 June 2013, 20:24:38
My old 3.2, and my old 99cdx discs went the same way, used daily. My current car is used on a shift system for work. The discs went the same way.

If it was metal quality, why wouldn't it affect the the whole disc...?

Calipers are designed to apply even pressure to both sides of the disc. Anything else would be unacceptable. Opposing piston calipers and single piston calipers like the omega seem to suffer the same.

I have seen the same issue on punto, golf, polo, BMWe39, focus, mondeo, since posting the same type of question a few years ago on here. I don't remember the calliper or splash guard design on those cars, but accepted that its not a problem specific to the omega.


...it seems to me that the splash/dust guard design on omega coincides with the rust line, at least to start with, in that the very bottom of the guard does not cover the bottom 10mm of the disc, and also leans away giving a bigger gap at he bottom.

Pinched this pic from Terry Pagets thread, so please ignore the stand, we've had that discussion, and focus the bottom of the disc and the guard.
https://www.dropbox.com/sh/f6kx9dg8ujqxp7t/jjxhb6lONv


Title: Re: Why do inner discs corrode?
Post by: chrisgixer on 18 June 2013, 20:31:48
Maybe it is the new style roadsalt, it (allegedly) has something in (animal fat? mollasses?) that makes it stick to the road for longer. Unfortunately it also sticks to windscreens, motorcycle helmet visors and (probably) brake disks.
I think that has a lot to do with the general car corrosion, but I don't think explains this scenario  :-\

Again, why not the whole disc? And just the inboard outer edge.


Also, as mentioned earlier, this affects the pads as well, which wear away in the adjacent area. IMO its the rust that swells the metal and takes more pad material away than the non rusty area.
Title: Re: Why do inner discs corrode?
Post by: chrisgixer on 18 June 2013, 20:50:37
Rear omega disc iirc. Shoes in shot for Andy P.  ;)

Notice that the chipped away part, on its left edge, lines up with a line across the face of the disc. Like the rust has eaten inward to the centre from the outside edge.

Although... The jagged lines that run across the face are very similar to the broken off leading and trailing edges of the pad. NOT the outer area, square with angled corners, but the area that actually touched the disc (its not uniform, like the leading and trailing edges of the pad have been chipped away).... its printed on the disc face in rust as caused when parked up from hot in damp conditions.

So two factors at play perhaps. The pad outline printed on the disc face in rust from parking up in the damp, and the outer band of corrosion.

(http://i344.photobucket.com/albums/p326/chrisgixer/02062009638.jpg)
Title: Re: Why do inner discs corrode?
Post by: dbdb on 19 June 2013, 01:41:32
I'm not sure why only the edge is affected but on mine the n/s front inner disc has much wider rust band than the o/s so I don't think it can be the shield design. 

Why the surface goes I now understand, once rusts starts if you don't brake hard only the surface will be removed, the rust continues to eat away at the steel and soon the actual steel (excluding the rust) becomes below the surface level of the unrusted surface.  From then on the pad will only touch the unrusted part and the rusted parts will just corrode more and more, with the pads occasionally scraping off some surface rust under heavy braking.

I plan to treat the rust with some rust convertor, at least that should slow down the corrosion and maybe the unrusted level will catch up with it.

My original discs lasted 190K miles.  The replacements fitted by VX started to rust after only a year.
Title: Re: Why do inner discs corrode?
Post by: tunnie on 19 June 2013, 09:00:09
I'm not sure why only the edge is affected but on mine the n/s front inner disc has much wider rust band than the o/s so I don't think it can be the shield design. 

Why the surface goes I now understand, once rusts starts if you don't brake hard only the surface will be removed, the rust continues to eat away at the steel and soon the actual steel (excluding the rust) becomes below the surface level of the unrusted surface.  From then on the pad will only touch the unrusted part and the rusted parts will just corrode more and more, with the pads occasionally scraping off some surface rust under heavy braking.

I plan to treat the rust with some rust convertor, at least that should slow down the corrosion and maybe the unrusted level will catch up with it.

My original discs lasted 190K miles.  The replacements fitted by VX started to rust after only a year.

 :o :o :o :o

Must have done mega miles in a short space of time, I thought 6 years and 70k odd at best was impressive  :-[  ;D ;D ;D
Title: Re: Why do inner discs corrode?
Post by: dbug on 19 June 2013, 15:31:03
I'm not sure why only the edge is affected but on mine the n/s front inner disc has much wider rust band than the o/s so I don't think it can be the shield design. 

Why the surface goes I now understand, once rusts starts if you don't brake hard only the surface will be removed, the rust continues to eat away at the steel and soon the actual steel (excluding the rust) becomes below the surface level of the unrusted surface.  From then on the pad will only touch the unrusted part and the rusted parts will just corrode more and more, with the pads occasionally scraping off some surface rust under heavy braking.

I plan to treat the rust with some rust convertor, at least that should slow down the corrosion and maybe the unrusted level will catch up with it.

My original discs lasted 190K miles.  The replacements fitted by VX started to rust after only a year.

 :o :o :o :o

Must have done mega miles in a short space of time, I thought 6 years and 70k odd at best was impressive  :-[  ;D ;D ;D

Thought your car only had 68K on it? http://www.omegaowners.com/forum/index.php?topic=115730.msg1463126#msg1463126 (http://www.omegaowners.com/forum/index.php?topic=115730.msg1463126#msg1463126)
Title: Re: Why do inner discs corrode?
Post by: tunnie on 19 June 2013, 15:35:08
Errrr one up the road is not mine  ::)
Title: Re: Why do inner discs corrode?
Post by: tunnie on 19 June 2013, 15:35:43
Stated many times mine are 164k & 141k :)
Title: Re: Why do inner discs corrode?
Post by: omega3000 on 19 June 2013, 15:46:37
You need some new boots   ::)


(http://i344.photobucket.com/albums/p326/chrisgixer/02062009638.jpg)
Title: Re: Why do inner discs corrode?
Post by: dbug on 19 June 2013, 16:27:00
Errrr one up the road is not mine  ::)

Not yous tun - dbdb's ;)
Title: Re: Why do inner discs corrode?
Post by: chrisgixer on 19 June 2013, 18:54:12
Anyway, this rust on one side but not the other...?


(Sigh...)
Title: Re: Why do inner discs corrode?
Post by: tunnie on 19 June 2013, 18:55:58
Errrr one up the road is not mine  ::)

Not yous tun - dbdb's ;)

D'oh. Sorry mate  :-[  :y
Title: Re: Why do inner discs corrode?
Post by: tunnie on 19 June 2013, 18:58:19
Anyway, this rust on one side but not the other...?


(Sigh...)

Remove pad every so often and clean up the disc  :-\ quite a quick job really.
Title: Re: Why do inner discs corrode?
Post by: chrisgixer on 19 June 2013, 19:08:22
Rust equals moisture. Once rusted too late.

How to stop the rust?

Suspect of the splash guard is extended to cover the disc to stop the rust, then there might be cooling problems...? (If you accept the short splash guard as the cause of course)
Title: Re: Why do inner discs corrode?
Post by: Andy H on 19 June 2013, 19:09:04
Maybe it is the new style roadsalt, it (allegedly) has something in (animal fat? mollasses?) that makes it stick to the road for longer. Unfortunately it also sticks to windscreens, motorcycle helmet visors and (probably) brake disks.
I think that has a lot to do with the general car corrosion, but I don't think explains this scenario  :-\

Again, why not the whole disc? And just the inboard outer edge.


Also, as mentioned earlier, this affects the pads as well, which wear away in the adjacent area. IMO its the rust that swells the metal and takes more pad material away than the non rusty area.
First stage - shiny new metal, new pads. All good :y
Second stage - light rust forms overnight. Gets swept off first application of brakes. No harm done. :)
Third stage - rust forms pits in the surface. Brakes sweep the surface rust off but the pits remain :(
Fourth stage - pits in disk surface cause accelerated wear of brake pad. Wear is uneven and pad edges wear first  :'(
Final stage - parts of the disc that rusted first (eg the edges) are allowed to rust in peace forming the big flakey rust  >:(
Title: Re: Why do inner discs corrode?
Post by: Andy H on 19 June 2013, 19:15:32
In the days of asbestos brake pads the discs seemed to last the life of the car.

Since asbestos free brake pads were introduced discs don't seem to last more than two sets of pads. If I get that life out of my disks I'm not going to lose any sleep over it.
Title: Re: Why do inner discs corrode?
Post by: worzelof10acrefield on 19 June 2013, 22:38:51
This was very common on the early fiestas. it does seem to be the ones without the splash sheild that do this. it is very common for certain cars to do this. the wife's galaxy which had discs and pads yesterday was just as bad and no it does not have splash shields either...
Normally it was just fiestas that did this but it has got a lot more common on newer cars.
Title: Re: Why do inner discs corrode?
Post by: chrisgixer on 19 June 2013, 22:42:23
Ok Andy, but why only the inside face?

And why only the outer edge?

Given rust equals moisture. :)
Title: Re: Why do inner discs corrode?
Post by: dbug on 19 June 2013, 23:23:07
More moisture on inner face - outer face has more protection from moisture - protected by wheel/tyre?

Just conjecture ;)
Title: Re: Why do inner discs corrode?
Post by: chrisgixer on 19 June 2013, 23:27:52
More moisture on inner face - outer face has more protection from moisture - protected by wheel/tyre?

Just conjecture ;)

Agreed ;D
Title: Re: Why do inner discs corrode?
Post by: henryd on 19 June 2013, 23:31:34
More moisture on inner face - outer face has more protection from moisture - protected by wheel/tyre?

Just conjecture ;)

Yep pretty much what I said in the 2nd post ;)
Title: Re: Why do inner discs corrode?
Post by: dbdb on 20 June 2013, 00:20:42
I'm not sure why only the edge is affected but on mine the n/s front inner disc has much wider rust band than the o/s so I don't think it can be the shield design. 

Why the surface goes I now understand, once rusts starts if you don't brake hard only the surface will be removed, the rust continues to eat away at the steel and soon the actual steel (excluding the rust) becomes below the surface level of the unrusted surface.  From then on the pad will only touch the unrusted part and the rusted parts will just corrode more and more, with the pads occasionally scraping off some surface rust under heavy braking.

I plan to treat the rust with some rust convertor, at least that should slow down the corrosion and maybe the unrusted level will catch up with it.

My original discs lasted 190K miles.  The replacements fitted by VX started to rust after only a year.

 :o :o :o :o

Must have done mega miles in a short space of time, I thought 6 years and 70k odd at best was impressive  :-[  ;D ;D ;D

Thought your car only had 68K on it? http://www.omegaowners.com/forum/index.php?topic=115730.msg1463126#msg1463126 (http://www.omegaowners.com/forum/index.php?topic=115730.msg1463126#msg1463126)

yes but I had one before, my original omega, 1998 had it from new til 2012
Title: Re: Why do inner discs corrode?
Post by: dbdb on 20 June 2013, 00:47:33
Not long back checking how thick the lip of the disk edge was on a car used to be a way to check if the miles were genuine.  I've never replaced a disk on any car I've had until my (original) mig and even then it was only after 14 years.