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Brake master cylinder and brake booster questions (R34)

V28VX37
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V28VX37 Veteran

V28VX37

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I've searched for these with no luck so here goes:

  1. Does anyone know where to get a BM50 brake master cylinder rebuild kit for the R34 GTT OEM BMC?
     
  2. Is the BM57 a plug-and-play upgrade over the BM50? Would I retain existing brake bias and ABS with it? The idea is to go bigger (front) brakes in the future so if upgrading BM57 is similar cost to rebuilding the BM50 that might be the go.
     
  3. Does anyone know if the R34 GT brake booster is the same as R34 GTT? The part numbers seem different but I'm not sure if the P/N is for the booster+master combo, and the GT master is definitely the smaller BM44.

Thanks guys.

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KiwiRS4T Grand Master

KiwiRS4T

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Have you tried Nissan for the rebuild kit? I put a BM57 in my S1 Stagea and retained the original brake booster.  I don't know if bias is different but I put a set of D2 330mm 8 pot brakes on the front and GTR 2 pot on rear and did not have any apparent problems with bias.

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V28VX37 Veteran

V28VX37

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2 hours ago, KiwiRS4T said:

Have you tried Nissan for the rebuild kit? I put a BM57 in my S1 Stagea and retained the original brake booster.  I don't know if bias is different but I put a set of D2 330mm 8 pot brakes on the front and GTR 2 pot on rear and did not have any apparent problems with bias.

Good idea, I'll give that a go.

Does your ABS work ok on gravel/wet with the bigger master?
I'm actually pretty keen on the 330mm rotor size so I could retain my 2 sets of 17" GTT stockies, both with decent tyres...

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KiwiRS4T Grand Master

KiwiRS4T

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24 minutes ago, V28VX37 said:

Good idea, I'll give that a go.

Does your ABS work ok on gravel/wet with the bigger master?
I'm actually pretty keen on the 330mm rotor size so I could retain my 2 sets of 17" GTT stockies, both with decent tyres...

Yes still got ABS. I believe D2 brakes sold in Aus as K sport or suchlike. Duncan has a set on one or more of his cars. Or GTR Brembos are 324mm. You may need to check if stock GTT wheels will fit over. I have used 17in Rays and 18in Skyline wheels.

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V28VX37 Veteran

V28VX37

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Have you pulled your MC apart to see if it is badly scored etc? If not a rebuild kit should be fine.

If you do want a new one Just Jap seem to have them for 395

http://justjap.com/catalogsearch/result/?q=Brake+Master+Cylinder


Thanks mate. I haven't pulled it out yet as I'd prefer at least installing some new seals before putting it back together.

I reckon I'll start with bleeding the abs unit as per the above instructions to see if that improves it at all.
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V28VX37 Veteran

V28VX37

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Has anyone heard of HFM or used their parts? Their BM57 alternative is a decent price, pic below: https://hfm.parts/shop/brakes/nissan-bm57-brake-master-cylinder-abs/

Looks like it's a Chinese re-manufacture of the original Nissan BM57: https://www.facebook.com/gktech/photos/a.479905785391677.98225.133362883379304/729676497081270/ 

HFM-BM57ABS.png

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admS15 Grand Master

admS15

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Do not use hfm bmc. Im not sure if anyone has had success with one but a lot of people have had major issues. The only parts they sell that are any good are their brake calliper adapters for R33 and S15. Just about everything else is junk unfortunately. I recently bought some of their calliper adaptors but wasn't game on trying out their rotors. LOL.

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V28VX37 Veteran

V28VX37

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I rang Race Brakes, they don't have the rebuild kit but suggested testing the master cylinder first.

I've just done the following:

  1. Car off
  2. Pump brake several times, stiff pedal
  3. Put tape measure next to the pedal
  4. Apply consistent brake pressure
  5. Measure pedal drop

I did this for 30 sec (max attention span) and there was zero pedal drop, so it seems like the master seals ok?

EDIT: I also just watched some vids on vacuum assisted brake boosters. I've always had this thing where in traffic lights, applying the same pressure, the pedal drop slightly after a while. Understanding now a bit more how a brake booster works, this could be the engine idle revs increasing ever so slightly > more vacuum > more brake boost > increased drop for same pedal pressure. Does this make sense?

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KiwiRS4T Grand Master

KiwiRS4T

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14 hours ago, V28VX37 said:

I rang Race Brakes, they don't have the rebuild kit but suggested testing the master cylinder first.

I've just done the following:

  1. Car off
  2. Pump brake several times, stiff pedal
  3. Put tape measure next to the pedal
  4. Apply consistent brake pressure
  5. Measure pedal drop

I did this for 30 sec (max attention span) and there was zero pedal drop, so it seems like the master seals ok?

EDIT: I also just watched some vids on vacuum assisted brake boosters. I've always had this thing where in traffic lights, applying the same pressure, the pedal drop slightly after a while. Understanding now a bit more how a brake booster works, this could be the engine idle revs increasing ever so slightly > more vacuum > more brake boost > increased drop for same pedal pressure. Does this make sense?

Yep. To confirm try the brake pedal first thing in the morning before starting the engine. Hit it a few times to make sure there is no vacuum left,  pause,  and then push down on the pedal and see how it feels.

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