Thread: Brake slack
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      01-12-2013, 12:43 AM   #13
sparoz
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Drives: VO 1///M; AW X3 30d
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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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