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      01-05-2020, 04:26 AM   #1
Setright
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ATE Ceramic pads and Zimmermann drilled discs

After having some serious scares on wet motorways I decided it was time for something other than plain discs. Speeds over 100km/h in rainy weather means the discs are covered in water, that takes just under a second to clear off with pressure on the middle pedal. That equates to 36 meters at the legal speed limit.

I find that quite disconcerting

Since wind and other conditions means the discs aren't equally wet, they also grip at slightly different times, meaning that I can expect a slight change of direction as I am pooping myself waiting for the brakes to work

I know the car periodically applies the brakes lightly when the rain sensor tells it too, with the aim of keeping the discs dry. It just isn't effective enough. I also know that this system has 3 settings. As well as the wet discs problem being "wheel design sensitive".

Anyway, seeking to solve this problem and reduce the dusting provided by factory pads I decided to fit ATE Ceramic pads and Zimmermann drilled discs. On all 4 corners.

Now, before you all tell me they will crack: This is a street car, that doesn't see any trackdays, so I am not worried.

I used to track an Impreza and have worn out many EBC grooved/dimpled discs and Mintex and Ferodo semi-track pads. However, there aren't that many options for a humble single-piston 300mm disc equipped F20. Front pads are especially limited as most aftermarket pads are for the 312mm fronts...or the M-Sport brakes.


Finding useful info this ATE/Zimmermann combination is close to impossible. Most posts are years old and usually filled with the same knee-jerk comments:
"Drilled discs crack" and "Ceramic pads don't work cold".

So! I have decided to conduct the testing and post my findings here, for other curious souls to read.

Right now I have only 200km on the new components, so they aren't even run-in, let alone bedded-in. I haven't been on a wet motorway yet, but last night, I drove in just barely freezing conditions and the brakes take effect immediately. That's nice to know


The real question here is: Does anyone care?

..and did I go on for too long for anyone to read this far
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      01-05-2020, 05:16 AM   #2
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I care, and I would easily have read 10x more about the subject. Several friends of mine have tested Zimmerman drilled discs, and they all got some small cracks eventually. The question is if it matters or not. As long as the car is not used for track driving, I think the probability for disc failure is very close to zero, even with small cracks.

The holes have a gradient, but as they wear down, this gradient will disappear, and then they will crack very easily.

I doubt that it would take much more than one revolution (less than 2 meters) of braking to clear the water off the discs in the wet. Coming from the west coast of Norway, I have done a fair share of driving in very wet conditions, both on roads and tracks. I have always had quick brake bite in the rain, even with solid discs.

If the brakes seem sluggish at first, it could also be knock-back. If you drive for a while without touching the brake pedal, the pads could be pushed a bit back from the discs, so you need significantly more pedal travel to apply the brakes again. The automatic wet maintenance braking helps against this too. Some racing drivers make a quick dab on the brake pedal with the left foot after straights, to make the brakes ready.

The way I see it, holes, grooves or dimples in the discs have two purposes. One is to save weight, and the other is to keep the pads clean. I have noticed that my overcooked brake pads take longer to recover with solid discs after a track weekend. The outer layer of the pads gets soft and slippery, and needs to be worn off before the brake pedal feel is back to normal.
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      01-05-2020, 06:43 AM   #3
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Rain It's not knock back, that would give a low pedal, but no delay. And it wouldn't disappear in dry weather.
It is in fact wet discs for sure. The conditions are quite well defined and I have a good friend with the same experience on a 320d M-Sport. I have also found posts on the web of people describing exactly the same conditions and symptoms. Could be the way the M-Sport bumpers channel cooling air for the brakes. My previous Sport (no M) had different ducting and wasn't that bad in the rain. (It also had different rims)

Do consider that factory pads have a long and very shallow chamfer. This forms a wedge with the disc that can hold a lot of water.

Cracks We have to see what happens. In favour of low risk is the street use (even if I do enjoy a winding road, it's never as hard on brakes as a trackday.)
The Zimmermann discs do seem to have evolved to reduce crack formation and propagation if/when they form. The holes aren't that large, chamfered* and none are radially aligned.

My choice of ceramic pads might be problematic, if indeed ceramic pads aren't good at conducting heat away from the pad/disc interface. Still, this is hard to verify because there are so many rumours and myths on the internet.


*Yes Ovekam, as you say, once worn away the straight edged holes will crack far more easily. However, the disc starts life 22mm thick and minimum is 20.4mm. Once the chamfer is worn away, the disc is strictly speaking ready for replacing anyway.

What pads were your friends running? What type of driving?
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      01-05-2020, 09:17 AM   #4
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I think you are right, and that the chamfering is improved compared to older Zimmerman discs.

My friends were running all sorts of pads, and the whole range from only street driving to frequent track days. Strangely enough, this did not seem to matter much.

At least you don't have to worry much about mountain passes in Denmark! :-D
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      01-05-2020, 09:29 AM   #5
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Yeah, we can stretch to something like 135 meters.
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      01-05-2020, 02:03 PM   #6
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Smile

Quote:
Originally Posted by Setright View Post
I decided to fit ATE Ceramic pads and Zimmermann drilled discs. On all 4 corners.
That's excessive. You should've tried it on 1 first.
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      01-06-2020, 02:16 AM   #7
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Quote:
Originally Posted by No one View Post
That's excessive. You should've tried it on 1 first.
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      01-07-2020, 01:15 PM   #8
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Preliminary results

Right, with roughly 1000km on the brakes now, they are close to run-in and I have starting using them harder. I am a stickler for proper running in of any mechanical device.

Cold Performance
Plenty of initial response. The rumours of bad cold performance all over the internet is either outdated or related to other brands. ATE Ceramic are ready when cold.

Dust
A thousand kilometers, including brand new discs and there has been almost no discernable dust. Either not much is being produced or it is simply not sticking.

Wet Weather
The discs with holes proved themselves today. Wet motorway and the brakes are ready at the first press of the middle pedal. I am very happy with that, since it was the driving force behind this modification.

Feel
I was hoping that the theory of ceramic pads being harder and less compressible would translate to a more solid feel in the brake pedal. It does!

The pedal moves to take up the natural slack in the system and then gets significantly more firm than with regular pads. This is not the level of a fully metallic pad, braided hoses and reinforced mount master cylinder...but a welcome firmness that gives me confidence and also allows for good modulation. For those, like me, with 3 pedals it also serves as a better fulcrum for heel-toe downshifts.


So quite good impressions so far. I have yet to properly bed the pads into the discs and take it for a more spirited drive on a winding road. I expect that under sensible road use there won't be any problems.

It is important to keep in mind that this a street car and ATE are quite clear about their ceramic pads being designed for "comfort".
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      01-07-2020, 03:11 PM   #9
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Sounds good!

But there are several ways to run in brake pads. One of them takes less than an hour.
Do 10 repeated hard stops from 100-20 km/h, then keep driving until the brakes are cold.
Finished! The important part is to never stop. If you need to stop, let the brakes cool down and start over. You will smell the brake pads during the procedure.

I have done this procedure with many sets of brake pads, and it works well. You will however need almost deserted roads, and it is easy to get slightly nauseous from the accelerating and braking.
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      01-07-2020, 03:38 PM   #10
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I am making a distinction between run-in and bed-in.

Straight out the box you should drive normally and avoid hard braking. The pad and disc surface need to wear into each other. That is "run in".

I know lots of internet posts suggest a sequence of progressively hard stops and then a cooling off, as soon as the brakes are mounted. That is a recipe for squeaking and shuddering brakes. I have seen a Youtube video where a big brand name mounts their newest discs and pads on a Mustang, without cleaning rust off the hubs...and then goes out and gives the brand new brakes hell, right out of the shop. I have also seen a lot of videos where buyers complain that this brand squeaks, squeals and shudders. I am drawing my own conclusions on the connection.

Zimmermann and ATE both recommend at least 300km of normal driving before any hard stops.

The idea is also to heat cycle the discs moderately, instead of giving them a shock. Steel is less fickle than many other alloys, but it is best to respect what heat cycling does to the internal structure. Allowing it to "normalize".

I have mounted countless brake discs and pads on my cars throughout the years and this method has provided good results every time
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      01-07-2020, 03:54 PM   #11
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Obviously with a bedding-in procedure once the run-in is complete. Repeated hard stops 'til the green fade arrives, then drive to cool it all down. Visual inspection of the discs surface should show a nice even colour change - the transfer layer.
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      01-07-2020, 03:58 PM   #12
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I have used the quick procedure on maybe 15 or so brake pad sets on my cars, and I have never had a squeak or shudder. I have also removed shudder from some friends' cars by rebedding the pads this way. I guess the manufacturers can't really recommend this kind of driving on public roads, and I am not saying it is better than the slow way. It is however an alternative for impatient drivers who want their brakes ready for action tomorrow, and I also have very good experience with it.

Aren't brake discs heat cycled from the manufacturer?
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      01-08-2020, 03:40 PM   #13
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I have no problems with us bedding brakes in, in different ways

With any semi-metallic I will use the same 100-20 as you describe, but I do give them 300 km of normal driving first.


Heat cycled discs? Well, with my educational background I assume that the discs are cast, cooled off in stages. Then machined (maybe at slightly elevated temperature), and then "normalized" in a heating and cooling staged cycle. The tension around the holes needs to be relieved. Remember, ALL discs have holes....one for the hub and 3,4,5 or 6 for the bolts

I do not expect normal street discs to have been heat cycled multiple times and not to anywhere near the temperature they reach on the road during a hard run.

The extreme temperature at the braking surface is not really possible to simulate in an oven anyway. This is where bedding becomes really important. I am going to simply here, so please don't nit-pick:

Heat attracts the carbon in steel. As the braking surface gets hotter than the rest of the disc, carbon will diffuse toward the surface and harden it. This is good for disc life. However, sudden thermal shocking can create uneven hardening and cause irreparable shudder. Sometimes, as you say Ovekam, you can cure judder with hard braking. Either you are evening out the hardness because there is enough carbon in the discs to allow that, and/or you are cleaning off an uneven transfer layer.


I am having a hard time finding any official recommendation from ATE on how to bed their ceramic pads. Considering the design philosophy these ceramic pads probably create a transfer layer on the disc without needing extreme heat or pressure. Designed for "comfort" and EU regulations, they likely don't need any special bedding for most normal use.

Last edited by Setright; 01-15-2020 at 01:53 PM..
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      01-11-2020, 06:23 AM   #14
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Update

With nearly 2000km on the brakes I am still happy.

I think the ceramic pads are much easier to modulate. They take effect quickly and are very responsive to pressure on the brake pedal. Yeah, that sounds funny when I re-read it, but they point is they are progressive, predictable and not grabby or snatchy.

I have had to stomp on the brakes twice for dozy people with no lane discipline. Instant and decisive reaction from the brakes. Even after many motorway miles with the brakes untouched and therefore cold (5 degrees C). So, cold bite, even at 130km/h is at least as good as the semi-metallic originals.*

When traffic on country roads has allowed I have braked hard repeatedly and not found any fading. Sure, cold weather and sensible public road driving shouldn't produce fade, but it's good to know that these pads aren't a downgrade in terms of street performance.

The pads have been hot enough to create a visible transfer layer. Since the ceramic principle is adhesive friction, I expect the layer to last longer than with a semi-metallic. Hot semi-mets make a great transfer layer too, and then brake really well. However, I find that they are quick to rub the layer off again in normal driving.





*If you want more, then I have good experience with DS Performance pads. Still legal, but much more agressive. Of course, they squeak and squeal...and dust even more than standard pads
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      02-05-2020, 01:21 PM   #15
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Now with 7000km on the brakes, the discs are just starting to lose the concentric rings machined into them from new. Not bad in terms of wear.

The performance of the brakes is still excellent. Alert and ready from frosty cold, progressive, predictable, powerful and with a firm positive pedal.

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