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      12-28-2012, 06:35 AM   #1
sparoz
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Brake slack

I have some brake slack after the installation of the Brembos, but it only happens on the initial application. If I release the brakes and immediately reapply, then the brakes work beautifully. However, after I drive for some distance, the slack is there again.

Anyone can shed light on the problem that would be very helpful.

Many thanks.
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      12-28-2012, 09:28 AM   #2
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Pad knock back? Would be hard to imagine given how high end the kit is, but I suppose it's possible. Is there any vibration while braking?
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      12-28-2012, 12:10 PM   #3
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Are you certain they were bled properly? If any doubt, do it again.

Neil
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      12-28-2012, 11:03 PM   #4
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Quote:
Originally Posted by E30 Racer
Pad knock back? Would be hard to imagine given how high end the kit is, but I suppose it's possible. Is there any vibration while braking?
No vibration at all and in fact it felt absolutely amazing after the initial slack where it doesn't seem to do anything.
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      12-28-2012, 11:06 PM   #5
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Quote:
Originally Posted by MDORPHN
Are you certain they were bled properly? If any doubt, do it again.

Neil
I would hope so especially I was charged 4 hours bleeding and testing the brakes as they have bled it six times. However I actually think this might be the problem.
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      12-28-2012, 11:34 PM   #6
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Quote:
Originally Posted by sparoz View Post
I would hope so especially I was charged 4 hours bleeding and testing the brakes as they have bled it six times. However I actually think this might be the problem.
I'm old school on brake bleeding. Even when I use my pressure bleeder to flush the fluid, I still always complete the process the old-fashioned way -- with a buddy sitting in the drivers seat pumping the brake pedal at my direction while I go from one caliper to the next for a final bleed.

If you have a floor jack and a workspace, it's an easy job and worth knowing how to do yourself.

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      12-29-2012, 03:46 PM   #7
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Neil, do use a tube to collect the old fluid? I would love to know if you see any bubbles coming out after a complete job with a pressure bleeder.
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      12-29-2012, 07:14 PM   #8
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Quote:
Originally Posted by CarJunkie View Post
Neil, do use a tube to collect the old fluid? I would love to know if you see any bubbles coming out after a complete job with a pressure bleeder.
Yes, and I generally find some bubbles.

Neil
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      01-01-2013, 06:18 AM   #9
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Okay, I finally managed the drive the car on the back roads today and have the brakes tested thoroughly. I have tried to bed them again - feeling a bit sick afterwards. The problem is still there, but I can now for certain say that the first stroke is spongie and it firms up if I pump the brakes.

Does that mean there's still air in the system?
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      01-01-2013, 11:18 AM   #10
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Certainly sounds like it. Have you discussed the issue with Brembo directly?
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      01-01-2013, 12:05 PM   #11
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I had the same issue when installing my Stoptech BBK. After the pads are somewhat bedded, go out and get the anti-lock to engage a few times. Then bleed the brakes using the two person method with the engine running. This worked for me. This was not required for subsequent fluid changes. A pressure bleeder works fine once all the air is removed from the system but it doesn't seem to build up enough pressure to push all the air out of the system. Also, I believe there is a way to activate the anti-lock system through the ECU, but I'm not sure how to do it?
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      01-01-2013, 06:19 PM   #12
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Quote:
Originally Posted by E30 Racer View Post
Certainly sounds like it. Have you discussed the issue with Brembo directly?
Not yet, as I think the problem is with the installation. The brake works beautifully once the pressure is up.

Quote:
Originally Posted by Pig Farmer View Post
I had the same issue when installing my Stoptech BBK. After the pads are somewhat bedded, go out and get the anti-lock to engage a few times. Then bleed the brakes using the two person method with the engine running. This worked for me. This was not required for subsequent fluid changes. A pressure bleeder works fine once all the air is removed from the system but it doesn't seem to build up enough pressure to push all the air out of the system. Also, I believe there is a way to activate the anti-lock system through the ECU, but I'm not sure how to do it?
Yeah, I will check if they have done the GT1 bleed.
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      01-12-2013, 12:43 AM   #13
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Like to update this thread to potentially help someone else with a brake problem. I found many people with similar problem, but the thread dies without any "resolution". I think things were fixed and they just never bother to post any feedback which I think is a bit selfish and disappointing.

Anyway, thanks to my Dad he's put on another 1000km on my car, and after I tried to rebed the car, I think the brakes had settled somewhat. The other day I wasn't able to string some good runs, but today I was able to get some very clean runs where I can test out the brakes.

The Good part:
The brakes are beautiful and easily modulated. It instils so much more confidence on getting the braking pressure right. No noise, no vibration, just slow down the way you want it to. This is a street test on country roads only, so the speed involve is not big like on the track, but I can feel what I have paid for. The other improvement is the suspension. Turn-in is quicker, sharper; road imperfections rarely unsettled the car where you can feel the full grip available. The car now has a much bigger head start when I start looking into suspension. Unfortunately haven't got a chance to test them on track yet, and looks like it is not going to happen till 28/3. Will try to get one in in February if the problems are sorted.

The problems:

I can distinct two problems which might be related:
1. The brake sometimes have no brake pressure when you lightly press on it and an audible click can be heard, and after that, the pressure will build up slowly initially, but it will just grab the brakes. It usually happens when I haven't brake for a while.
2. When I am in some of braking rhythm, the audible click is gone. However, there is a minor slack before pressure builds up. However, once the slack was gone, the brakes were absolutely fantastic. The slack is predictable, and doesn't actually bother me that much.

So, I am starting to think there is potentially two problems. I think problem 2 is definitely a bit of air in the system which I can cope with for now - and it is consistent so no real concerns. This also pretty much eliminate and MC mismatch.

The first problem might a bit harder to diagnose, but potentially I might have a sticky leading piston that falls too far away? So when the second and piston grab, it really slows down the car? It might not be aligned properly during install? Or there are some loose hose in the system that wasn't tightened? It could still be an air issue after the air no longer aggregate with each other?

Anyway, will report back once it is all sorted.
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      01-12-2013, 10:09 AM   #14
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What a joke!

How much did you pay for this system and who installed it. For the lack of technical and customer support from both, I find your experience totally unacceptable.
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      01-12-2013, 10:32 AM   #15
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I still think the problem is air in the system. I think you may want to read the following technical write-up and consider how this could be exaggerated by air in the system:

http://www.stoptech.com/technical-su.../pad-knockback
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      01-13-2013, 01:17 AM   #16
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Quote:
Originally Posted by bdaddylo View Post
How much did you pay for this system and who installed it. For the lack of technical and customer support from both, I find your experience totally unacceptable.
Nothing wrong with the vendor as I haven't alerted him yet, becuase I strongly believe it is an installation issue. As for the installer, I haven't got a chance to take it in, but I was a bit disappointed that they sent me back the car when it wasn't right and tell me that it is. We have a good relationship, and they are happy for me to take the car back when I have a chance, but I think it may be beyond their technical expertise and hence I want to make sure I analysis the problem before I take it back in.
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      01-13-2013, 01:20 AM   #17
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Quote:
Originally Posted by Pig Farmer View Post
I still think the problem is air in the system. I think you may want to read the following technical write-up and consider how this could be exaggerated by air in the system:

http://www.stoptech.com/technical-su.../pad-knockback
Many thanks for this! I finally plugged in my Solo DL yesterday and I am pretty convinced that it is also air.

1. Car off, very little play - ie not the paddle.
2. Car on, the brake sensor show no pressure until what it felt like an inch before it senses pressure.
3. Brakes feels good after the initial slacks taken down - unlikely MC mismatch.
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      01-13-2013, 09:59 AM   #18
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And why you don't just go out to your garage for 30 minutes and rebleed?
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      01-13-2013, 01:02 PM   #19
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Quote:
Originally Posted by robertm
And why you don't just go out to your garage for 30 minutes and rebleed?
Agree! KISS principle.
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      01-13-2013, 02:27 PM   #20
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One other thing that can cause a soft pedal is a loose or worn wheel bearing. This will let the rotor wobble or shimmy and move the brake pads out some. Then when you NEED to brake... the pedal will feel soft.

I would really suggest you bleed your brakes again. IF you don't feel confident go to another shop. A good shop should not charge you more than 1 hour to bleed your brakes. You might also have them use a rubber hammer and tap each brake caliper as they bleed them. Sometimes you can get trapped air inside of them.

Also on most BBK there are TWO brake bleed screws. Make sure they bleed both with a pressure bleeder.

I bought a Motive Brake bleeder years ago... worth its weight in gold. Saved my butt so many times when bleeding brakes by myself.
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      01-13-2013, 05:45 PM   #21
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Quote:
Originally Posted by robertm View Post
And why you don't just go out to your garage for 30 minutes and rebleed?
Quote:
Originally Posted by M3 Adjuster View Post
Agree! KISS principle.
I am scared of my wife telling off that I don't spend enough time with them . Seriously, I am considering this too, but not very confident with doing it myself.

Quote:
Originally Posted by Dackelone View Post
One other thing that can cause a soft pedal is a loose or worn wheel bearing. This will let the rotor wobble or shimmy and move the brake pads out some. Then when you NEED to brake... the pedal will feel soft.

I would really suggest you bleed your brakes again. IF you don't feel confident go to another shop. A good shop should not charge you more than 1 hour to bleed your brakes. You might also have them use a rubber hammer and tap each brake caliper as they bleed them. Sometimes you can get trapped air inside of them.

Also on most BBK there are TWO brake bleed screws. Make sure they bleed both with a pressure bleeder.

I bought a Motive Brake bleeder years ago... worth its weight in gold. Saved my butt so many times when bleeding brakes by myself.
Thanks for this Dac!
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      01-17-2013, 05:59 AM   #22
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Finally, I got it sorted today and thanks everyone for the help. So, it is just air in the system after all, and the mechanics I went to have an ATE pressure bleeder and got all the air out in the first go. However, they were just checking the work done and also found that the pins and spring on the rear brakes wasn't inserted properly, and they have fixed the loud click that I have.

So, that confirmed Brembo did a fantastic job in engineering the part to suit stock MC and a larger one is not needed for a brake upgrade if the kit doesn't come with it.

So hopefully this will help someone to diagnose the problem if they have similar issue.
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