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      02-07-2021, 06:18 PM   #1
eggman51
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Question Aftermarket Brake Master Cylinders ?

Hey Folks,

I am going to replace my brake master cylinder. After a fair amount of troubleshooting, it seems like the seals are not holding pressure.

My car is a 2006 Z4M Radster. I have an AP Racing BBK on the fronts from Essex. I track the car a fair bit.

The master cylinders are quite expensive, so I want to make sure I have the right part, or, ideally, find an aftermarket part.

I believe the BMW part # for a 2006 Z4M is: 34317838638

Are there any good quality track friendly aftermarket brake master cylinders I should consider?

Are there any other considerations when replacing the brake master cylinder for a car that sees lots of track days?

Thanks!
Eamonn aka eggman

Last edited by eggman51; 02-07-2021 at 07:45 PM..
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      03-01-2021, 02:33 PM   #2
elerner61
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I need to change my master cylinder as well and haven't found any alternatives. My fluid is turning dark in the reservoir (non-tracked car) in less than a year. It would appear the seals in the mc have started to deteriorate after 14 years. Wish there was a rebuild kit.
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      03-01-2021, 08:45 PM   #3
eggman51
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I spoke with a few qualified people and they all recommended the BMW master cylinder, even for performance applications. The part number is listed above which appears to supersede an older part number. Some of us may have that older part. I have no idea if there is anything wrong with the older parts.

I could not find any rebuild kits for our cars.

I will be replacing my master cylinder in April as part of my track season prep. I have an Essex / AP Racing bbk on the fronts and stock brakes in the rear. The pedal feel degraded materially since I started tracking the car so I am hoping the master cylinder fixes that.

Cheers
Eamonn
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      03-04-2021, 07:20 AM   #4
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Quote:
Originally Posted by eggman51 View Post
I spoke with a few qualified people and they all recommended the BMW master cylinder, even for performance applications. The part number is listed above which appears to supersede an older part number. Some of us may have that older part. I have no idea if there is anything wrong with the older parts.

I could not find any rebuild kits for our cars.

I will be replacing my master cylinder in April as part of my track season prep. I have an Essex / AP Racing bbk on the fronts and stock brakes in the rear. The pedal feel degraded materially since I started tracking the car so I am hoping the master cylinder fixes that.

Cheers
Eamonn
Let us know how this goes and if it is an increase in pedal feel.
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      03-04-2021, 08:58 AM   #5
wss4
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Make sure you bench bleed the master cylinder during installation. Impossible to get a normal pedal feel on this car without doing so, in my experience.
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      03-04-2021, 09:12 AM   #6
eggman51
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Quote:
Originally Posted by wss4 View Post
Make sure you bench bleed the master cylinder during installation. Impossible to get a normal pedal feel on this car without doing so, in my experience.
What does bench bleed entail? My indie is an enthusiast shop, but I don’t want to make any assumptions they understand our cars to this level of detail.
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      03-04-2021, 09:38 AM   #7
wss4
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You essentially fill the brake master cylinder and reservoir outside of the car, attach some fittings and hoses to the outlet ports that recirculate fluid into the reservoir, and pump the piston by hand to bleed out any air. I rotate master cylinder through a range of inclination while pumping piston to make sure air doesn't get trapped anywhere. At least that's how I did it, and it made a huge difference versus installing without doing so.

The only tricky part is the removal of the fittings/hoses and installation of brake lines once positioned in the car. You have to be quick so that you don't lose too much fluid or introduce air.
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