shuddering when braking

AdrianHi

It's funny how on threads like this someone who knows points out it's not warped disks, because that never happens, but others continue to talk about warped disks.

The patches of Cementite that have built up causing a raised surface on the disk can be skimmed. The cementite can penetrate to a fair depth which attracts further build up so don't be surprised if the problem re-occurrs.
This problem can be avoided by correct bed in procedure when you have new pads fitted and makign sure you don't do things like brake hard from speed, come to rest with your foot on the brake where some pad material then wleds itself to the disk surface which then begins the cycle of pad material build up which under the heat from braking forms cementite which attracts more brake pad material and eventually juddering when braking.
More detail here: http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

Between 1500 and 80,000 miles on my previous car I had the disks skimmed 3 times then took the on car to 122,000 miles all on the same disks.

mikey72

AdrianHi wrote: »

It's funny how on threads like this someone who knows points out it's not warped disks, because that never happens, but others continue to talk about warped disks.

The patches of Cementite that have built up causing a raised surface on the disk can be skimmed. The cementite can penetrate to a fair depth which attracts further build up so don't be surprised if the problem re-occurrs.
This problem can be avoided by correct bed in procedure when you have new pads fitted and makign sure you don't do things like brake hard from speed, come to rest with your foot on the brake where some pad material then wleds itself to the disk surface which then begins the cycle of pad material build up which under the heat from braking forms cementite which attracts more brake pad material and eventually juddering when braking.
More detail here: http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

Between 1500 and 80,000 miles on my previous car I had the disks skimmed 3 times then took the on car to 122,000 miles all on the same disks.

I've had warped disks, cracked disks, and generally knackered disks.
If it starts on a Mondeo at 111000 it's probably not because they weren't bedded in properly, so lets just agree a new set of disks and pads will sort it out.

(Any more sources that hold to that theory apart from that one by the way, or other third party quotes of the website)

somech

pretty much say 50k on discs THEY ARE WORN OUT and WARPED

AdrianHi

mikey72 wrote: »

I've had warped disks, cracked disks, and generally knackered disks.
If it starts on a Mondeo at 111000 it's probably not because they weren't bedded in properly, so lets just agree a new set of disks and pads will sort it out.

(Any more sources that hold to that theory apart from that one by the way, or other third party quotes of the website)

A design engineer in the automotive industry whoes specialisation is research and investigation into problem areas in car design and ways of trying solving them. He put me on to that article in the first place.
If the disks had been skimmed in the past and worn a little you would be getting down to the embedded cementite material which would then start to attract pad material and cause the build up.

Anyway, new disks and pads, or skimming the old ones if there is still enough "fat" on them to be in specification and then following good bedding in procedure should sort the problem.
If the plan is to keep the car longer term I'd go with new disks.
This sort of issue car effect new cars or cars with new disks.

mikey72

AdrianHi wrote: »

A design engineer in the automotive industry whoes specialisation is research and investigation into problem areas in car design and ways of trying solving them. He put me on to that article in the first place.
If the disks had been skimmed in the past and worn a little you would be getting down to the embedded cementite material which would then start to attract pad material and cause the build up.

Anyway, new disks and pads, or skimming the old ones if there is still enough "fat" on them to be in specification and then following good bedding in procedure should sort the problem.
If the plan is to keep the car longer term I'd go with new disks.
This sort of issue car effect new cars or cars with new disks.

So, no other articles, as I've never seen anything but that one ever quoted either.
To the last line, what about old mondeos with 111000 miles, and no other work done?
(If you skim a warped disk, it cures it as well)

spark_deals

LandyAndy wrote: »

Could it be a fault that is operating the ABS when it isn't required??

+1
Cracked reluctor ring

mikey72

AdrianHi wrote: »

A design engineer in the automotive industry whoes specialisation is research and investigation into problem areas in car design and ways of trying solving them. He put me on to that article in the first place.
If the disks had been skimmed in the past and worn a little you would be getting down to the embedded cementite material which would then start to attract pad material and cause the build up.

Anyway, new disks and pads, or skimming the old ones if there is still enough "fat" on them to be in specification and then following good bedding in procedure should sort the problem.
If the plan is to keep the car longer term I'd go with new disks.
This sort of issue car effect new cars or cars with new disks.

It's been years since I did any metallurgy, so I'm sure someone can put me right.
If I can remember.
Grey cast iron, is the normal cast, cooled slowly, fairly soft,and used for discs.
White cast iron is hard, with the carbon as cementite. But to make white cast you have to quickly cool the molten iron. White cast forms on the outside, as it's hard to cool all the way through.

So heating the normal disk, then cooling slowly doesn't sound as though it should form cementite, and skimming the surface shouldn't get down to cementite, in fact it should remove anything.

Maybe

AdrianHi

mikey72 wrote: »

It's been years since I did any metallurgy, so I'm sure someone can put me right.
If I can remember.
Grey cast iron, is the normal cast, cooled slowly, fairly soft,and used for discs.
White cast iron is hard, with the carbon as cementite. But to make white cast you have to quickly cool the molten iron. White cast forms on the outside, as it's hard to cool all the way through.

So heating the normal disk, then cooling slowly doesn't sound as though it should form cementite, and skimming the surface shouldn't get down to cementite, in fact it should remove anything.

Maybe

Metallurgy is not my field but the way it's described it's the combination of material from the brake pad initially transferring to the disk surface when the pad is pressed hot onto the surface followed by the accumulation of more brake pad material (dust) which always coats the surface of the disk that conspires to increase the cementite deposits which embed into the disk surface.