Strange way of brakes bedding in

[46lukasz]

Hello all,

I replaced my brake discs and pads recently and something strange is happening.

I bought Brembo extra drilled (rear) and dimpled (front) discs, and Zimmermann pads for both ends. I did a really thorough job, cleaned and inspected everything, degreased with brake cleaner multiple times before installing, and measured the run-out of the disc when on the hub. I also painted the calipers while everything was taken apart.

The car brakes well and there are no vibrations.



Let me explain everything in chronological order and get to the issue.

I started with the rear brakes. After replacing I took the car for a spin and everything worked fine, nothing unusual.

After doing the front, I had some clicking noise when not applying brakes and some noise when applying brakes.
Upon reading about dimpled/drilled/slotted discs, it appears that it is their characteristic to be somewhat noisy.
The clicking noise when not applying brakes went away after a short time.

Because I test drove the car after doing the rear, it would mean these noises are only coming from the front, but the rear is also drilled so I'm confused?

I did about 200km of gentle driving and did not brake hard to allow the brakes to bed in.
The rear seems to be bedding in fine, pads appear to be depositing some material on the face of the disc, but it doesn't look like it's happening for the fronts, like at all.

After the car sat for a while and there were some rust spots on the discs, I took it for a spin and the rears were cleared to bare metal when I got back but the front looked like the rust got smeared around instead of clearing off. I know you can't smear rust but that's what it looked like.

Yesterday I took it for a spin again and decided to step on the brakes a bit harder this time. The car was braking well, no vibrations or anything, but it looks like the front discs were once again unphased by the stress they were put under. They aren't even shiny. The rear discs turned slightly brown.

Are the front discs not working well with these pads? Have I been practically braking with mostly the rear all this time? Have I started to overheated the rears?
Here are some pictures what it looks like after some harder braking. Rear is slightly discolored and the front are slightly shiny just on the outside edge.

front:


rear:

 

[45bvtc]

Hello all,

I replaced my brake discs and pads recently and something strange is happening.

I bought Brembo extra drilled (rear) and dimpled (front) discs, and Zimmermann pads for both ends. I did a really thorough job, cleaned and inspected everything, degreased with brake cleaner multiple times before installing, and measured the run-out of the disc when on the hub. I also painted the calipers while everything was taken apart.

The car brakes well and there are no vibrations.

View attachment 268537View attachment 268538

Let me explain everything in chronological order and get to the issue.

I started with the rear brakes. After replacing I took the car for a spin and everything worked fine, nothing unusual.

After doing the front, I had some clicking noise when not applying brakes and some noise when applying brakes.
Upon reading about dimpled/drilled/slotted discs, it appears that it is their characteristic to be somewhat noisy.
The clicking noise when not applying brakes went away after a short time.

Because I test drove the car after doing the rear, it would mean these noises are only coming from the front, but the rear is also drilled so I'm confused?

I did about 200km of gentle driving and did not brake hard to allow the brakes to bed in.
The rear seems to be bedding in fine, pads appear to be depositing some material on the face of the disc, but it doesn't look like it's happening for the fronts, like at all.

After the car sat for a while and there were some rust spots on the discs, I took it for a spin and the rears were cleared to bare metal when I got back but the front looked like the rust got smeared around instead of clearing off. I know you can't smear rust but that's what it looked like.

Yesterday I took it for a spin again and decided to step on the brakes a bit harder this time. The car was braking well, no vibrations or anything, but it looks like the front discs were once again unphased by the stress they were put under. They aren't even shiny. The rear discs turned slightly brown.

Are the front discs not working well with these pads? Have I been practically braking with mostly the rear all this time? Have I started to overheated the rears?
Here are some pictures what it looks like after some harder braking. Rear is slightly discolored and the front are slightly shiny just on the outside edge.

front:
View attachment 268535View attachment 268536

rear:
View attachment 268534

With respect, I usually follow a different (Brembo) procedure, such as follows:

Brembo Brake Bedding-in procedure:
The purpose of this procedure is to gradually increase the temperature in the components without thermal shock and to mate the brake pad and disc friction surfaces, generating a uniform transfer layer.

Procedure Part 1:
• Perform 20 (ish) brake applications slowing from 60mph to 20mph
• Allow 15-20 seconds between each brake application
• Use medium deceleration, approximately 60% of maximum
• DO NOT brake to a stop! (Friction deposits are likely to 'bond' to the brake disc and you will believe you have a warped brake-disc...)
• When completed, drive the vehicle for at least 5 minutes with little or no braking allowing the brake discs and pads to adequately cool
• The system is now ready for normal use

Note: When it can be done legally, or on a closed circuit, a secondary bedding operation is beneficial.

Procedure Part 2: Repeat the above procedure for 5 to 10 brake applications increasing the starting speed to 80mph and increasing the deceleration rate to 80% of maximum. After completion, drive the vehicle for at least 10 minutes with little or no braking in order to adequately cool the components.

IMPORTANT: This entire procedure must be complete before driving the vehicle as normal. It is especially important that this process be completed before any extended same-speed driving is done (i.e. Motorway travel). Failure to follow these instructions greatly increases the likelihood of judder development."

 

[Simon]

Just to add I've had drilled disks for years and never noticed clicking when braking

 

[45bvtc]

Just to add I've had drilled disks for years and never noticed clicking when braking

Same here: drilled front and rear on our RS3, SQ5 and TT; zero 'clicking' when braking.

 

[46lukasz]

Hi guys, thanks for the input. Regarding the bedding in procedure, I had a look through the instructions that came in with the discs, they did mention to avoid very heavy breaking immediately after installing, but they were nowhere near as detailed as you posted.

Although I didn't do the hard breaking procedure and braked gently instead, I did pay attention to not come to a complete stop when the brakes are hot, and to allow them to cool down while driving before parking the car. I guess I will keep driving and hope for the best, nothing else I can do at this stage.

The fact that the front discs are starting to have some pad material deposited on the outer edge, looks like it could still be fine.

Regarding the sounds, this video is the best I could find to demonstrate the clicking sound I had for the first few km of driving, when not braking at all.
That sound is gone now thankfully.


This video is similar to the sound I have during braking, although mine is not that bad. I can't hear it unless I am braking next to a wall with the window open.
Hopefully this will go away over time as well.

 

[Simon]

It is not uncommon to go through the hard bedding process again to clear uneven pad deposits so even after doing the gentle process the hard way is still an option.

 

[46lukasz]

So i followed your advice and did the hard bedding process again to see what will happen. I found a short stretch of road with roundabouts at each end and just did a couple laps like that, breaking when approaching the roundabouts

There was something starting to happen on the surfaces of the front rotors, although its clear that one side is doing something else than the other (these pictures were taken the morning after)


So i went to do it again
Fronts looked a lot better i think there is some visible transfer layer forming, and the rears got darker in the middle, not sure what's that about



after another round they look like this:


At this point i think i am happy. The brakes are performing better, with a significant improvement in the initial bite.
I still think i should have went with same brand pads and discs, under the assumption that they are designed to work together, I think that this combination of disc and pads just doesnt work together that well, but it will do for now.

 

[46lukasz]

**********CONTINUED**********

Frankly I am not sure what to expect to see to call it a fully created transfer layer. I searched online and saw a few example pics.
according to the first pic, bedded discs are more shiny with a blueish tint.
according to the second pic, the discolouration i have on the rears is normal.
according to the third pic, a blue colour shows brakes well bedded in, but looks like overheated to me (they are performance brakes on the pic so different rules could apply)
The 4th pic is of my other car, where brembo discs and pads are used. Although a bit worn at this stage, you can see almost a gritty surface, where I assume metalic pieces of pad are embedded in the disc. I would consider them well bedded in, they work great.

I look forward to your comments

 

[Simon]

I would be less concerned with how they look than how they feel, and if they feel good then I’d call it a win.

 

[46lukasz]

Yeah, i can't complain about performance now, but i hope to learn something out of it
I already learned a bit from the bedding in process, but i think it created more questions than answers

 

[45bvtc]

Yeah, i can't complain about performance now, but i hope to learn something out of it
I already learned a bit from the bedding in process, but i think it created more questions than answers

Then here is another interesting article for you and again highlighting the importance of the 'bedding-in' process:

The myth of warped brake discs

Have you ever heard someone say they had warped brake discs? Typically someone had the discs resurfaced to cure the problem and after a relatively short time the roughness or vibration came back. In almost every case, this problem is not caused by a warped discs, but that the brake pad...

alconkits.com

Hope this helps

 

[46lukasz]

thanks for that, that's a very good read, and that's why I was putting such an importance on getting a proper transfer layer on the discs, and in turn that's why i was checking on how they look.

i might put upload some more pictures after some more milage just to update how they are doing.

do you know if i was to change the pads right now, can i just do the bedding in again or does the surface of the disc need to be cleaned off of the old pads transfer layer?

 

[45bvtc]

If the brake discs are 'clean' 46lukasz, as are yours, then I'd fit new pads and undertake a bedding-in procedure to both 'cure' the friction material and apply a 'transfer' layer to the brake disc.
Again, I do so like/prefer/use Ferodo Eco-Friction brake pads for road work, see: https://www.audi-sport.net/xf/threa...drilled-discs-ferodo-eco-friction-etc.429427/

 

[46lukasz]

just had a look, these pads are not that expensive either! And you are giving them glowing reviews, ill give them a try whenever the current ones are worn

 

[46lukasz]

after i thought its going to be fine, the saga continues...
the car was sitting for about 2 weeks, sometimes it rained, discs developed some surface rust, then after quite a long drive the right disc is fine, the left one looks like the surface rust was just smeared across it.
on every other car i dealt with, the discs were cleared and shiny after the first few brakings,

the car still brakes well but i cant help but wonder.

 

[Simon]

I'd be inclined to strip, clean and lubricate those calipers

 

[46lukasz]

it crossed my mind that the caliper is at fault but I'm positive that its working OK
everything was cleaned and lubricated when I was putting these brakes on, as i took a lot of care at every step
I pulled back the dust cover slightly to check the piston, and there was absolutely no corrosion under it, piston was in great shape.

when jacked up, the wheel rotates freely so caliper is not sticking, and then stops rotating when brake is pressed.
the discs also heat up evenly as i checked this after a spirited drive.

the only thing that comes to mind is that these pads really don't go well with these discs, but i would expect any pad to clear any disc simply due to friction.

since last post i took it for another drive with some hard braking to clear it again, and the disc is mostly clean except one area, it's bizarre

 

[Simon]

are the discs directional? perhaps swap from one side to th eother and see if it clears up , could be an issue with the disc material itself - would be super odd but potentially possible.

 

[45bvtc]

it crossed my mind that the caliper is at fault but I'm positive that its working OK
everything was cleaned and lubricated when I was putting these brakes on, as i took a lot of care at every step
I pulled back the dust cover slightly to check the piston, and there was absolutely no corrosion under it, piston was in great shape.

when jacked up, the wheel rotates freely so caliper is not sticking, and then stops rotating when brake is pressed.
the discs also heat up evenly as i checked this after a spirited drive.

the only thing that comes to mind is that these pads really don't go well with these discs, but i would expect any pad to clear any disc simply due to friction.

since last post i took it for another drive with some hard braking to clear it again, and the disc is mostly clean except one area, it's bizarre

View attachment 269747

See your own post #14: "just had a look, these pads are not that expensive either! And you are giving them glowing reviews, ill give them a try whenever the current ones are worn". I think you'd best do it now...

Here's our 2010 TT after 100 miles (Welshpool - Llanfair) on Thursday:


And our 2011 RS3 after 100 miles (Rudyard Lake) yesterday:

Note the lack of brake dust...

Hope this helps

 

[46lukasz]

I gave in and replaced the front pads with Ferodo Eco-Friction FDB4045 about 1000km ago.
I can say right away that the initial bite and brake modulation is better with them. And they also clear all the surface rust off the rotor right away.
Even though Zimmermann pads work OK on the rear, I will stay away from them in the future.


Before:


After Right Side:


After Left Side:


As you can see I now have a few rings on the right side that haven't really cleared. Not sure what that is about.
Initially I thought its a grove left by the old pads, but when I run my finger nail across it, its level with the disc, not lower or higher than the disc surface.

I hope it will clear as well, because its looks botched.

 

[46lukasz]

in desperation i got some 800 grit sand paper and cleaned off the face of the rotor. After a quick drive here is how it looks.
visible lines are still there, where the pad doesn't contact the rotor, which would mean there is a low spot on the pad - possibly caused by the surface rust or whatever it was left on by the previous set of pads.


I guess i could take the pad out and sand it flat again?

lucky me...

 

[45bvtc]

in desperation i got some 800 grit sand paper and cleaned off the face of the rotor. After a quick drive here is how it looks.
visible lines are still there, where the pad doesn't contact the rotor, which would mean there is a low spot on the pad - possibly caused by the surface rust or whatever it was left on by the previous set of pads.
View attachment 272380 View attachment 272379

I guess i could take the pad out and sand it flat again?

lucky me...

How many miles have you done 'braking!'

Be patient, stop 'flatting' them discs and/or pads, it'll ALL clean up once the 'pad' is bedded to the disc-surface

Question: have you actually done this?
"• Perform 20 (ish) brake applications slowing from 60mph to 20mph
• Allow 15-20 seconds between each brake application
• Use medium deceleration, approximately 60% of maximum
• DO NOT brake to a stop! (Friction deposits are likely to 'bond' to the brake disc and you will believe you have a warped brake-disc...)
• When completed, drive the vehicle for at least 5 minutes with little or no braking allowing the brake discs and pads to adequately cool
• The system is now ready for normal use"

 

[46lukasz]

Yes i did that procedure, maybe not exactly down to the seconds between each brake application but i found a road with 2 roundabouts and did a few laps with medium breaking before turning around.

Yeah i realise i probably can just let the pad bed in all the way, or in other words get worn down past the low spot, so I'm not sweating it.
it is already a lot better than it was anyway

 

[45bvtc]

Yes i did that procedure, maybe not exactly down to the seconds between each brake application but i found a road with 2 roundabouts and did a few laps with medium breaking before turning around.

Yeah i realise i probably can just let the pad bed in all the way, or in other words get worn down past the low spot, so I'm not sweating it.
it is already a lot better than it was anyway

And as most of your braking is on the FRONT it the take the REARS longer to bed in.

Plus, if you've a 'mechanical' control handbrake then use that, carefully...

Oh, and when you've the opportunity, put the Eco-Friction on the rear too

 

[46lukasz]

So after driving for 4k km since replacing the front pads with Ferodo set, here is what they look like. They have bedded in enough that the rings on the left wheel are gone.



Things are looking a lot better but both sides are still bedding in, as the outer edges where the pad should touch the disc are still rusting and only silver dots are showing.

I mostly do motorway driving so bedding in slow

Now looking at the rears, I'd say they would also benefit from Ferodo pads



I guess the short message is stay away from Zimmerman pads everyone

 

[Simon]

good feedback and nice to see an update

 

[45bvtc]

good feedback and nice to see an update

Well done Simon

I still maintain Ferodo Eco-Friction the best, and most probably cheapest, brake pad I've used for road-work: still using 'em on 'our' TT, RS3 and SQ5 and NO complaint.

Seemingly VERY brake disc friendly with NO brake squeal, and LOW brake dust!

They do what expected just perfectly.

No wonder Audi and Mercedes are using them for OEM.

 

[issacdyels]

This is just a fantastic place to learn new things!

 

[Simon]

Ferodo are fine pads to use, I always rated Pagid as decent as well. Currently I am running EBC Yellowstuff on the S4 front and rears, I can't actually remember what I have on the GTR!