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Would you remind me how old are discs and pads?
If you are trying to break in used pads and rotors you are wasting your time .... Must be done from new. If you must drive to where the break in will take place, like from the shop if you're having someone else do the work, slow, slow, light pedal pressure only, stop way short and creep at stop lights. You know, the kind of driving that pisses you off when you're behind them :)
 

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Would you remind me how old are discs and pads?
Rear discs and pads very new but not brand new. Front pads very new but discs about two years old.

I'll just grin and bear it as what with this engine noise I've got I'm not throwing any unnecessary money at this car.
 

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Discussion Starter · #205 ·
Rear discs and pads very new but not brand new. Front pads very new but discs about two years old.

I'll just grin and bear it as what with this engine noise I've got I'm not throwing any unnecessary money at this car.
My car was sitting several months when I was sorting out the engine. Could be surface rust? My current discs are also worn about 20-30%. They look shiny and very clean. However at least 3years old.
 

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My car was sitting several months when I was sorting out the engine. Could be surface rust? My current discs are also worn about 20-30%. They look shiny and very clean. However at least 3years old.
After four sessions of brake bedding as per those instructions there's not a hint of surface rust anywhere lol
 

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Discussion Starter · #207 ·
After four sessions of brake bedding as per those instructions there's not a hint of surface rust anywhere lol
Oh yes, I meant when it is not driven for some time, some areas may have more surface rust. Then when cleaned, does areas will be deeper. At least areas under pads possibly will have leas rust.
 

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Oh yes, I meant when it is not driven for some time, some areas may have more surface rust. Then when cleaned, does areas will be deeper. At least areas under pads possibly will have leas rust.
Ah ok I see.

The thing which puzzles me is that I can't believe that every car which leaves the factory goes through this process (or do any at all?), nor do any garages do this after fitting new discs/pads. So if this process is so essential, then surely every car which hasn't gone through it would have judder?

I have never done this bedding in process before in my life and also never had a car until Jaguar which had brake judder. So, I'm more inclined to think that this is a component issue with a part or parts that Jaguar (and perhaps some other brands/models) use or have spec'd and this process is perhaps a method to deal with such components and the resulting judder?
 

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Ah ok I see.

The thing which puzzles me is that I can't believe that every car which leaves the factory goes through this process (or do any at all?), nor do any garages do this after fitting new discs/pads. So if this process is so essential, then surely every car which hasn't gone through it would have judder?

I have never done this bedding in process before in my life and also never had a car until Jaguar which had brake judder. So, I'm more inclined to think that this is a component issue with a part or parts that Jaguar (and perhaps some other brands/models) use or have spec'd and this process is perhaps a method to deal with such components and the resulting judder?
Absobloodylutely.
186738
 

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Discussion Starter · #210 ·
Ah ok I see.

The thing which puzzles me is that I can't believe that every car which leaves the factory goes through this process (or do any at all?), nor do any garages do this after fitting new discs/pads. So if this process is so essential, then surely every car which hasn't gone through it would have judder?

I have never done this bedding in process before in my life and also never had a car until Jaguar which had brake judder. So, I'm more inclined to think that this is a component issue with a part or parts that Jaguar (and perhaps some other brands/models) use or have spec'd and this process is perhaps a method to deal with such components and the resulting judder?
Same here. I just read the info sheet that came with pads. It says it is essential to do break in according to car’s manufacturer instructions. There is nothing like that recommended by Jaguar. It also says avoid harsh brakes or continuous application for brake to speed up the break in.
 

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Discussion Starter · #211 ·
Car still is on jack stands for 5days now. I only spend 1hr a day so it goes slowly. I am doing brakes, diff oil, transmission fluid, brake fluid, leaking AC line and possible slow oil leakage from the valve cover that I replaced several months ago.

So far what I have observed is that all wheel hubs are not flat more or less. Meaning rust or antiseize is somehow fused into hub surface and like impossible to remove. I am sure judder will be back prematurely if I leave it like that.

Also although slider pins are free and clean, they will seize up when I warm them to what I consider a low temperature under driving conditions.
 

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An issue with hubs constantly comes to mind for me. It's the only possible problem considering how some people constantly have issues no matter what pads/discs combo they use and some people never seem to have any issues at all (luckily me).

Whether or not that exacerbates the pickup between the pad and disc isn't for me to say but it certainly seems to be a factor.
 

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I agree and I think there is something about my XF brake judder that appears unique to this car. I have had 8 different cars (both new and second-hand, large and small) and have never experienced this before, either in Scotland or Germany.
It is not a high performance racing car and should not require professional brake bed-in procedures, although I completely agree this may help prevent uneven cementite build-up on disks.

With respect to hubs I am also not too sure this is the main problem.
The new front hubs that I installed a couple of years ago came as very solid units with the large bearing attached to the hub. They should not deform by rusting in any significant way once pressed in and bolted onto the arm.
Even if the angle of the attached disk does not sit absolutely 100% "flush" with the caliper position, it should not result in hub run-out. This is because the calipers should have some degrees of freedom (they "float" a bit) with respect to how they hold the pads to the disks. I do not think a fractional tilt in angle of the hub in any direction will cause juddering - because such angle tilts should not give rise to disk run-out/wobble if the hub/bearing runs true.

It will remain a mystery to me and I now simply accept that I need to buy a new set of disks once a year (at least!).
It would prevent me from buying an XF again to be honest, even though I really like it.
 

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The calipers float as a means to allow them to adjust as the friction material alters. They're not really designed to float fast enough to take into account undulations in the surface of the disc.
 

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Discussion Starter · #215 ·
I agree and I think there is something about my XF brake judder that appears unique to this car. I have had 8 different cars (both new and second-hand, large and small) and have never experienced this before, either in Scotland or Germany.
It is not a high performance racing car and should not require professional brake bed-in procedures, although I completely agree this may help prevent uneven cementite build-up on disks.

With respect to hubs I am also not too sure this is the main problem.
The new front hubs that I installed a couple of years ago came as very solid units with the large bearing attached to the hub. They should not deform by rusting in any significant way once pressed in and bolted onto the arm.
Even if the angle of the attached disk does not sit absolutely 100% "flush" with the caliper position, it should not result in hub run-out. This is because the calipers should have some degrees of freedom (they "float" a bit) with respect to how they hold the pads to the disks. I do not think a fractional tilt in angle of the hub in any direction will cause juddering - because such angle tilts should not give rise to disk run-out/wobble if the hub/bearing runs true.

It will remain a mystery to me and I now simply accept that I need to buy a new set of disks once a year (at least!).
It would prevent me from buying an XF again to be honest, even though I really like it.
If the hub is not flat or disc doesn’t sit flat on hub, you will have lateral movements in each turn between disc surface and pad/calliper or brackets. I agree floating calliper should make up for this. My tests shows the rubber around sliding pin grabs it so tight when warmed up to 30-40degrees. I couldn’t move it by hand.
 

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Discussion Starter · #216 ·
I watched some videos and I am convinced the rust on hub surface could cause this. Even though I spent 1hr cleaning hub surface with wire brush on a drill, I did start to chip the dirt off by a screw driver following a video on utube. They do come off even do wire brush couldn’t. I ordered hub surface cleaner that sits around studs that should arrive tomorrow morning. I feel I can save the hubs. Also, I am going to drill the sliding pin rubbers with a 13mm drill bit to make it bigger. I am not sure if it works. The idea is to have pins free when calliper gets hot.
 

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If the hub is not flat or disc doesn’t sit flat on hub, you will have lateral movements in each turn between disc surface and pad/calliper or brackets. I agree floating calliper should make up for this. My tests shows the rubber around sliding pin grabs it so tight when warmed up to 30-40degrees. I couldn’t move it by hand.
I not sure what you mean by "hub not flat". I of course agree that the disk will have lateral movement each turn (wobble) if the disk is not completely flat against the hub surface, however the hub itself (assuming it is running true from factory) will not cause disk wobble by itself, even it is is fractionally askew.

Phil1, I did not mean to imply that the floating calipers will absorb disk fluctuations, only minute angle offset of how disc is positioned wrt the caliper.
 

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I watched some videos and I am convinced the rust on hub surface could cause this. Even though I spent 1hr cleaning hub surface with wire brush on a drill, I did start to chip the dirt off by a screw driver following a video on utube. They do come off even do wire brush couldn’t. I ordered hub surface cleaner that sits around studs that should arrive tomorrow morning. I feel I can save the hubs. Also, I am going to drill the sliding pin rubbers with a 13mm drill bit to make it bigger. I am not sure if it works. The idea is to have pins free when calliper gets hot.
sorry, I think I misunderstood what you meant originally. I assumed you were referring to the surface between the hub and where it attaches to on the car (suspension arm).
Now I see that you refer to the surface between the hub and the disk...
 

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Also, I am going to drill the sliding pin rubbers with a 13mm drill bit to make it bigger. I am not sure if it works. The idea is to have pins free when calliper gets hot.
Yes, I was also thinking of doing this however chickened out at last minute as I thought it could potentially do more harm than good if not drilled out perfectly...
Will be interesting to see your results.
 

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Discussion Starter · #220 ·
sorry, I think I misunderstood what you meant originally. I assumed you were referring to the surface between the hub and where it attaches to on the car (suspension arm).
Now I see that you refer to the surface between the hub and the disk...
Yes it looks clean, cannot catch anything by finger nail but some areas are dark and others shiny. I hope this tool kit works. I would be shocked if all 4 hubs are warped.
The movements between hub and axle will be due to bearing and that was within tolerance.
Also, when I focus on dark spots, measured runout improves.
 
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